Gulf

This basin comprises rivers which drain the southern Zagros Mountains to the head of the Persian Gulf, but which are not now tributaries of the Tigris River nor are they the salt streams of Hormozgan. None of these rivers has a significant fishery. At its northern edge, the Zohreh River flows across the Khuzestan plains and is close to Tigris River tributaries. Other major rivers are the Helleh, which debouches into the Gulf north of Bushehr (28°59'N, 50°50'E) and the Mand or Qarah Aqaj (= the classical Sitakos), which, with its tributaries, drains much of Fars Province to the Gulf south of Bushehr. Near Shiraz it is known as the Qarah Aqaj or Kavar River. The Band-e Bahman, a weir or small dam on this river near Kavar, is probably pre-Islamic.

The Mand River is 480 km long and occupies a basin of about 60,000 sq km. Its flow is reduced by a low snow cover (although there can be torrential spring flow), water seepage, evaporation and abstraction for irrigation purposes. Discharge has been estimated to range from 10-2025 cu m (Merchant and Ronaghy, 1976). It is also polluted near Kavar (29°11'N, 52°44'E) by sewage and agriculture residues and does dry up to a series of isolated pools there. A fish kill, numbering in the many thousands, occurred in the Mand near Shiraz in 1977 and was attributed to chemicals used in spraying against malarial mosquitos. The people hired to spray village houses either dumped quantities of the chemical into the river to reduce their work load or washed out containers in the river (Coad, 1980c). Temperature range is at least 20C° between winter and summer. The delta of the Mand is a Protected Area of 46,700 ha. There are thin oxbow lakes and associated marshes.

The Mand has a number of tributaries, at least two of which are called Shur (= salt) River. Conductivity near Firuzabad on the Shur River is 695-715 µM/cm but rises to 20,000 µM/cm below salt domes further downriver. The more southerly headwaters are close to those of the Shur River of the Hormozgan basin between Darab (28°45'N, 54°34'E) and Fasa (28°56'N, 53°42'E). The headwaters of the Mand lie north-west of Shiraz near Kuh-e Tabask at 2318 m (29°52'N, 51°49'E) and there are a series of springs in this area called Chehel Chashmeh (= Forty Springs) which feed the Mand. Nearby is the Dasht-e Arzhan (29°39'N, 51°58'E), a small enclosed basin with a flooded plain encompassing about 24 sq km at maximum. It is fed by small springs and streams. The water is fresh since swallow holes in the southeast corner of the plain drain water away with a salt flushing effect. Shiraz was once "chiefly supplied with fish from this lake" (Ouseley, 1819-1823) but it does not now support such a copious ichthyofauna. A report from Reuters (8 June 2000) cites a fish kill numbering in the hundreds of thousands from the "Arjang lagoon, in a suburb of the southern city of Shiraz", presumably this lake, after it dried up (www.iran-sabz.org/news/fish2.htm). The Haft Barm-e Kudian lie about 20 km north of Dasht-e Arzhan at 29°49'N, 52°02'E at 2200 m. The seven lakes lie in rolling country and the largest is about a 1 sq km. Some may dry up in certain years but fish were found suggesting that there is a perennial water supply (Cornwallis, 1968a). Scott (1995) says the southern 5 lakes generally dry out completely in summer. In winter the lakes freeze over. They are about 2-3 m deep and some are slightly saline. These lakes have been stocked with Esox lucius, Hypophthalmichthys molitrix, Ctenopharyngodon idella and Gambusia holbrooki.

Surber (1969) gives some spot data on pH, total alkalinity, calcium-magnesium hardness, chlorides and free CO₂ in the Mand basin. Near Firuzabad, the concentration of total dissolved solids is 333 mg/l while near Jahrom it reaches 6937 mg/l, indicating how there can be great variations in habitat within the same river basin over short distances, depending on local geology.

The Zohreh River and its tributary the Shul, are over 400 km long and have their headwaters near Kuh-e Barm Firuz at 3673 m (30°25'N, 51°58'E) whose northern flank spawns the Khersan River, a Karun tributary in the Tigris basin. Its basin is estimated to be 15,500 sq km. The Kowsar Dam at Gachsaran is 337.5 m high, its crest is 126 m and the reservoir capacity is 450 million cu m (http://netiran.com/news/IRNA/html/941126IRGG10.html). Gorjipoor et al. (2007) carried out a limnological investigation of the Zohreh River.

The Helleh River receives the Dalaki (205 km) and Shapur (231 km) rivers which drain the lower Zagros ranges west of Shiraz. Its basin is estimated to be 20,300 sq km (Shiati (1989) gives 10,000 sq km) and includes Lake Famur. Shiati (1989) gave an account of salinity in the rivers of this basin. Saline springs and salt domes increase the salinity about 10 times as the rivers flow down from the mountains. Total dissolved solids in the upper reaches of this basin are 366 mg/l, rising to 4219 mg/l in the lower reaches. Geological sources of sulphur also add to the chemical make up of these waters. There are no important sources of industrial pollution along these rivers but humans, domestic animals and agriculture are the main pollution sources. The levels of pollution are in the acceptable range (Gh. Izadpanahi, pers. comm., 1995). Aquaculture in the area (Helleh and Mand river basins) has not had obvious effects on coastal water quality (Omidi, 2006). The delta of the Helleh River is a complex of brackish and fresh marshes and lagoons with a maximum depth of 3.5 m. It is the largest freshwater marsh system on the Persian Gulf coast in southern Iran. It is designated as a Protected Area (42,600 ha). This area developed in the early 1970s when the main river channel was diverted onto the coastal plain.

A cave at Bishapur above the Shapur River is reputed to house a deep lake full of fish but this has not been investigated and may only be a local legend (Mounsey, 1872).

Endorheic Lake Famur, Perishan or Parishan (29°31'N, 51°48'E) is a particular feature of the Gulf basin which encompasses 42 sq km at about 820 m near Kazerun, is fed by about 80 fresh and brackish springs with a discharge of about 800 litres/second and supports a fish fauna near the springs. In years of heavy rainfall the fresh areas expand only to contract in dry years.

The ringing marshes are eutrophic and have halophytic plants of the genera Salsola, Kochia, Camphorosma and Halocnemum along with extensive reedbeds of Phragmites communis and Typha. This marshy shore attained 31°C in early June when air temperature was 43°C. Maximum depth is about 6 m, falling in summer to 3.87 m. pH is 7-8. The drainage basin encompasses about 290 sq km. Conductivity is 5 to 6,000 micromhos.

Södergren et al. (1978) recorded pollution in fish from this lake and the Shapur and Kupor rivers. Only small amounts of the organochlorine chemical p,p^'-DDE were found in the lake but the rivers had very high levels of DDT and its metabolites DDE and TDE. At this time DDT was used for indoor spraying against malaria-infected mosquitos and insecticide containers were cleaned in the rivers after spraying.

An account of the lake is given in Farsi by Maafi (1996a; 1996b; 1996c). The lake is eutrophic and low concentrations of oxygen periodically cause fish mortalities. The reed beds are set on fire to increase the available agricultural land and this results in a sediment input with the consequent decrease in water depth, fingerling habitat destruction, and fish mortality through sediments clogging gills. Overfishing is also a problem. Wastewater and sewage enter the lake untreated and this enhances algal growth and eutrophication. Fishery ponds are established west of Lake Parishan resulting in exotic escapes. During periods of low rainfall, Parishan becomes a shallow saline lake and presumably fish habitat is limited to the immediate vicinity of freshwater springs.

Lake Parishan and the nearby Dasht-e Arjan (29°37'N, 51°59'E) are a Ramsar Site (World Conservation Monitoring Centre, 1990). They lie within the Arjan National Park and International Reserve which encompasses 65,750 ha as established in 1973. However the Park has been downgraded to a Protected Area of 52,800 ha with the Ramsar Site being the wetlands of Lake Parishan at 4200 ha and Dasht-e Arjan at 2400 ha (Khan et al., 1992). Dasht-e Arjan at 1950 m is a shallow, eutrophic freshwater lake fed by runoff, precipitation and the Salmon springs. The lake area in winter may be 1950 ha but shrinks in summer to a few hundred hectares. It dried completely in 2001. There is an outflow through swallow-holes in the south-east, traditionally linked to Lake Parishan. The lake margin and the spring-fed marshes have Phragmites communis, Typha and Juncus along with aquatic vegetation. Dasht-e Arjan is cooler than the environs of Lake Parishan because of its higher altitude - 15-35°C in summer and -10-15°C in winter as opposed to 22-40°C and 5-15°C.

As well as the rivers described above, springs and qanats are important in the Gulf basin. The Dalaki mineral springs have a temperature range of 30-38°C and a discharge of 200l/s. They are at 130 m above sea level and their hydrology, geology and chemistry is reviewed in Kompani-Zare and Moore (2001). The fishes in this area have not been investigated.

Rabbaniha et al. (2003) surveyed the larval ichthyofauna in the Farakeh Creek estuary area in the northern Gulf and found 15 families to be represented, Clupeidae, Gobiidae and Sillaginidae making up almost 94% of the catch.

The Shabankareh Dam is a diversion dam in the lower Helleh River basin and several other dams have been planned for this basin. Small canals or diversions are also present in this basin (Borowicka, 1958).

Berg (1940) places this basin, the Hormozgan basin and the Makran basin as part of the Sind Province of the Indian Subregion of the Sino-Indian Region. Its eastwards extent is the lower and middle Indus River. The Iranian portion is called the Southern Iranian District. Small southern Iranian rivers belonged to a single river basin in the Pliocene, facilitating dispersal according to Berg.

Hormozgan

The Hormozgan basin comprises a number of intermittent streams and rivers which drain to the Straits of Hormuz. None of the rivers has a significant fishery. The basin has a catchment of 55,800 sq km. Rainfall is low and sporadic at this southern end of the Zagros Mountains and streams are not always perennial. Qanats are an important feature and there is a hot spring (41°C) at Genu (27°26'N, 56°20'E) just north of Bandar-e Abbas. This area of Iran is rich in salt domes rising to over 1200 m above the surrounding land surface and consequently surface water is often contaminated and stream banks are rimed with salt (Lehner, 1944; Shearman, 1976; Kent, 1979). Some of the islands off this coast are salt plugs, e.g. Hormuz Island. Temperatures in winter are high in the lower streams, 15-33°C, and must be much higher in summer. These warm and saline streams are home to the endemic cichlid, Iranocichla hormuzensis, and so are distinguished from the fresh waters to the north, east and west. This species has been collected in the Minab River where my collections in the 1970s did not find it. The Minab River was therefore included in the Makran basin but may well form the easternmost part of this basin. However the possibility of an introduction of this species to the Minab cannot be ruled out.

The principal river is the Kul with its tributary the Shur (= salt) River. The upper reaches of the Shur lie west of Darab (28°45'N, 54°34'E) and mountains here exceed 3000 m. The headwaters of the Shur approach those of the eastern tributaries of the Mand River basin. The lower valleys parallel the coast and drain eastwards. The Rasul River is a tributary of the Kul, while the Mehran River drains directly into the sea. The Mehran delta lies in the Hara Protected Area (Biosphere Reserve) described by Zehzad et al. (1998). The offshore islands such as Qeshm, are poor in fresh water, but have not been explored. A number of streams cross the plain east of Bandar-e Abbas (27°11'N, 56°17'E) draining the Kuh-e Furgun at 3279 m and associated ranges. Although many streams are salty, a freshwater oasis is found at Sar Khun (27°23'N, 56°26'E).

Several islands in the Persian Gulf are included as part of this basin. The largest island is Qeshm but it lacks rivers although there are some small dams to collect rainwater runoff (A. R. Zeanaie, pers. comm., 1999). Species observed are Aphanius dispar, a mudskipper and the introduced Gambusia holbrooki. Water temperatures reach 32°C.

Makran

The Makran is the coastal region of southeastern Iran between the Straits of Hormuz and the Pakistan border. In the west of this region the relief runs in a north-south direction parallel to the coast but from Jask eastwards the relief runs west-east, again paralleling the coast, to the Pakistan border. The rivers and streams of the Makran all drain to the sea at the Straits of Hormuz and the Sea of Oman. The inland Hamun-e Jaz Murian basin is isolated by mountain ranges reaching peaks in excess of 2000 m. The coastal drainages are often incised and the larger watercourses pass through tangs over 1000 m deep (Harrison, 1968).

I have not seen the watercourses between Jask and the upper Geh (= Nikshahr, Kaeyr or Kalar) River drainage (mouth is at 25°37'N, 60°08'E) but descriptions by Harrison (1941) indicate they are similar to other areas of Makran. It seems probable that only the Minab and Sarbaz Rivers have, or nearly have, a perennial and continuous flow along most of their course. Even these rivers are quite shallow and the Sarbaz in particular is easily fordable on foot along its entire length (ca. 280 km). The Minab River flows over a shorter course (ca. 220 km) than the Sarbaz, but has a greater flow regime. At Minab (27°09'N, 57°05'E) and at Rudan (27°26'N, 57°12'E) the Minab River was up to 100 m wide with an estimated maximum depth in pools of 2-3 m. The lower Sarbaz River was a series of shallow, muddy pools in the bottom of a canyon with some water flowing over sills connecting the pools (in early December 1977). The lower Sarbaz has been designated a Wetland of International Importance. In its middle and upper course the Sarbaz varied from a very shallow and narrow stream connecting pools (some of which were fishless) to what must be termed a river in the semi-desert environment of Baluchestan, with a width of 10 m, a depth of about 1 m and fast current. The rockfill embankment Pishin Dam built over the rivers Pishin and Sarbaz is 63 m high, has a crest length of 400 m and can store 175 million cu m of flood waters (http://netiran.com/news/IRNA/html/930418IRGG10.html).

The other streams of the Makran have little running water, often become isolated pools a kilometre or more apart, and regularly dry up along much of their length. Several rivers between the Mazavi (= Geru) River (mouth is at 26°56'N, 56°56'E) and the port of Jask are named and marked prominently on maps, but these were all dry in their lower reaches in late November 1976. Some flow in their upper reaches is to be expected, but its extent will depend on topography and recent climatic conditions. A dam and irrigation network is to be constructed on the Jaghin River east of Jask (IRNA, 26 June 2000).

Coad (1997a) combined the basins of the Makran, Lut, Jaz Murian, Mashkel and the Pakistani Pishin Lora as a single entity, expanding on earlier work by Mirza (1980). Mirza proposed the name Gedrosia for the Baluchistan Plateau west of the Central Brahui and Hala Ranges in Pakistan. The easternmost river along the Makran coast is the Hingol in Pakistan. East of this river the fauna becomes much more diverse at all taxonomic levels and the fauna is an Indus River one. In the north, the Pishin Lora River basin lies partly in Pakistan and partly in Afghanistan. Beyond this basin to the north and northwest lies the Registan Desert and then the Sistan basin, with its distinctive faunal mix including schizothoracines (Schizothorax, Schizocypris and Schizopygopsis) and a crested loach (Nemacheilus rhadineus). To the northeast lies an area designated as Yaghistan by Mirza (1980), with its unique faunal association. The westernmost river is the Dasht, whose upper reaches cross the Iranian border. The western limit of Gedrosia is the Mashkel River basin which has several tributaries from Iran. Coad (1997a) proposed that the limits of Gedrosia be extended westwards to encompass the Iranian part of the Mashkel basin, along coastal Makran as far west as the Minab River, and internally to include the Jaz Murian and southern Lut basins. West of the Minab River, the fauna was deemed to be unique in having an endemic cichlid, Iranocichla hormuzensis and in having members of such Euro-Mediterranean and Southwest Asian (= Middle East) cyprinid genera as Barbus, Chalcalburnus (= Alburnus), Leuciscus (= Squalius) and the cobitid genus Cobitis not found further east. However specimens of Iranocichla hormuzensis have been collected from the Minab River by H. R. Esmaeili (examined by me in 1997) and this river may properly belong to the Hormozgan basin. I did not collect this species in the 1970s and it is possible that the record is an introduction since that time from adjacent rivers as there have been many accidental movements of fishes in Iran associated with fish farming.

Generally basins within Gedrosia appear most closely related to their geographical neighbours and support the argument for containing these endorheic basins in one division. No basins are strongly and uniquely linked although Makran and Jaz Murian uniquely share Garra persica and Channa gachua, and Mashkel and Makran uniquely share Aspidoparia morar and Nemacheilus baluchiorum.

At the species level Gedrosia is most closely related to the adjacent Yaghistan and Indus basins to the east, then to the adjacent Sistan and Hormozgan basins, and least of all to the remoter Tigris-Euphrates basin. Its principal relationships are eastern, to some extent northern and very little to the west.

The generic pattern is different from the species one. The Sistan basin has the highest share of genera, followed by Yaghistan and Hormozgan. The Indus and Tigris-Euphrates share far fewer genera but they have a greater diversity (5.8 and 2.3 times that of Gedrosia). It is therefore not surprising that Gedrosia shares proportionately more genera with immediately neighbouring basins whose fauna at the generic level is also limited. However, omitting genera found in all basins or unique to a single basin, reveals that Yaghistan and Indus share 5 of 7 such genera exclusively with Gedrosia. Only Capoeta shows a different pattern being found in the western basins but not Yaghistan and Indus. The last genus is Crossocheilus which is found in the Indus, Yaghistan and Sistan basins. Therefore, generic level comparisons also show that Gedrosia is most closely related to the east.

The transitional nature of Gedrosia is evidenced by its having the distributional limits of certain wide-ranging species. This is most notable for species reaching their westernmost limits, namely Aspidoparia morar, Crossocheilus latius, Channa gachua, Labeo dero, Puntius sophore, and Tor putitora (the last three not recorded from Iran). Species are probably limited by environmental conditions such as temperature in comparison with the warm waters of South Asia. However a significant factor, as recognised by local people, must be the poor physical condition of Baluchistan. Freshwater marshes, lakes and large rivers are all absent. Desiccation of water bodies is common and many streams are intermittent. Habitat diversity for fishes is severely limited. All the common fish species are non-predatory - most fishes feed on small insects or scrape aufwuchs from the rocky stream beds.

In contrast to western limits, only one species has a distribution which is principally Southwest Asian and reaches its eastern limit in Gedrosia, namely Capoeta damascina. The remaining species have distributions which are centred on Gedrosia and immediately adjacent basins. There is also a link northwards in that some species have an extensive north-south distribution, namely Garra rossica, Nemacheilus kessleri and N. sargadensis.

One of the most interesting features of Gedrosia is its paucity of fishes. Diversity is low, presumably a result of the physical conditions noted above, compounded by desiccation and during climatic variations both past and present. Gedrosia is presumably an important former route of dispersal for taxa from South and Southeast Asia to Southwest Asia and beyond. The significant absences are of taxa found in the Tigris-Euphrates basin to the west and in the Indus basin to the east.

At the family level, five families are found both west and east, but not in, Gedrosia. These are Cobitidae, Bagridae, Siluridae, Sisoridae and Mastacembelidae. No cobitid or silurid genera are shared. They may be quite ancient and their absence from Gedrosia is by a vicariant event or their dispersal was via a northern route to the Tigris-Euphrates and separately to the Indus. The most significant absences are of such genera as Mystus in the Bagridae, Glyptothorax in the Sisoridae, Mastacembelus in the Mastacembelidae (Mastacembelus is not found in eastern Iran and hence does not have a continuous range throughout the Orient (pace Travers (1984)), and also Barilius in the Cyprinidae. The last three genera are found in drainages entering the upper Persian Gulf separate from the Tigris-Euphrates basin but probably had a recent connection with that basin during the Pleistocene lowering of sea levels when the Gulf was drained.

Berg (1940) suggested that fish dispersal across this region was facilitated by the coastal rivers of Iranian and Pakistani Baluchestan being part of a single river system in the Pliocene, since submerged by subsidence. This distribution of these genera is not, therefore, a remnant of the dispersal across Iran from Asia. It is possible that the Pleistocene fore-deep of the Himalayas had connections with the Tigris-Euphrates basin which extending down the Persian Gulf as a river valley. Hora (1937) and Menon (1957) refer to wet, marshy, tropical conditions and headwater captures along the whole southern face of the Himalayas and westwards during the Pliocene and early Pleistocene facilitating the spread of fishes from the east to what is now Southwest Asia (= Middle East) and Africa. However, it is here considered unlikely that the Tigris-Euphrates and Gedrosian rivers were once tributary to the Indus when sea levels were lower during glaciations as the Gulf of Oman descends to an abyssal plain at 3340 m as noted above. These taxa probably reached the Tigris-Euphrates basin across the Iranian land mass and subsequently became extinct as desiccation increased. Their absence from Gedrosia is probably by loss.

Hora (1937) and Briggs (1987) consider that cyprinids entered Africa from southeast Asia 18-16 MYA, in the early Miocene, while other groups moved through Iran and the Arabian Peninsula beginning in the early Eocene. Kosswig (1951; 1952; 1955a; 1955b) notes the similarity at the generic level between Indian and African fishes, e.g. the cyprinids Barilius, Garra and Labeo, indicating that these fishes arrived in Africa from India after the desiccation of the Syrian-Iranian Sea in the Pliocene. The primary route, according to Kosswig and to Por (1987), was a northern one around the barrier of the Persian Gulf and Sea of Oman via northern Arabia, Syria and the Levant. Cooling conditions in these areas, and presumably too in Gedrosia, during the Pliocene and especially the Pleistocene glaciations, and arid climates at times, were unsuitable for tropical forms.

Potential endemic taxa are Cyprinion milesi, N. bampurensis (in Iran), Labeo gedrosicus, Labeo macmahoni, Nemacheilus baluchiorum, and N. brahui (in Pakistan). The systematic position, as species, of Cyprinion milesi and Labeo gedrosicus need further study, and the distributions of the three Nemacheilus species are in contention. Endemism may be relatively high or low dependent on the resolution of these problems.

Fishes in the easternmost part of the basin have a unique predator to contend with among Iranian species. The gandoo (marsh crocodile or mugger, Crocodylus palustris) is found in the Sarbaz, Khaju and Bahu Kalat rivers including the Pishin Dam, makeshift lagoons and fish culture ponds. It is feeds on Cyprinus carpio and Periophthalmus (Crocodile Specialist Group Newsletter, IUCN, 18(1), WWW Edition, downloaded 16 December 1999 from www.flmnh.ufl.edu/natsci/herpetology/newsletter/news181b.htm; report by A. Mobaraki; A. Mobaraki, pers. comm., 2000). The Cyprinus carpio are escapees from fish farms.

Tigris River

The Tigris-Euphrates basin is the largest and most important river system between the Nile and the Indus. Details of its biology can be found in Rzóska (1980) but comparatively little is based on the Iranian part of this basin although Nümann (1966) gives some limited data on chemical and physical parameters. Studies on limnology and pollution were restricted mostly to waters of Iraq, but probably apply equally well to Iran, certainly as far as those marshes which cross the border are concerned and for the Shatt al Arab, part of which forms the southern border of Iran and Iraq. Such studies include Cressey (1958a), Jacobsen and Adams (1958), Al-Hamed (1966c), Mohammed (1965; 1966), Salonen (1970), Al-Saadi and Arndt (1973), Al-Sahaf (1975), Al-Saadi et al. (1975), Arndt and Al-Saadi (1975), Antoine and Al-Saadi (1982), Maulood et al. (1979; 1981; 1993), Sarker et al. (1980), Saad (1978a; 1978b), Saad and Antoine (1978a; 1978b; 1978c; 1982; 1983), Saad and Kell (1975), Kell and Saad (1975), Al-Hamed (1976), Al-Daham et al. (1981), Huq et al. (1981), Schiewer et al. (1982), Antoine (1983), DouAbul et al. (1987; 1987; 1988), Abaychi and Al-Saad (1988), Abaychi et al. (1988), Mohamed and Barak (1988), Al-Saadi et al. (1989), Hussain et al. (1991), Kassim and Al-Saadi (1995), Partow (2001), among others. Ionides (1937) describes the river regimes of the Tigris-Euphrates basin, MacFadyen (1938) the water supplies, El Kholy (1952) the hydrology of the Tigris River, Buringh (1957) the physiographic regions, shores and irrigation systems on the lower Mesopotamian plain, and Al-Khashab (1958) the water budget of the Tigris-Euphrates basin, mainly referring to waters in Iraq. Scott (1995) gives details of wetlands in Iraq, some of which border and/or are contiguous with Iranian wetlands, and whose general ecological features are very similar. Shapland (1997) reviews water disputes in the Middle East although western Iranian rivers flow out of the country and are not likely to be affected apart from any losses in shared habitats or refuges in border areas.

Por and Dimentman (1989) regard the Tigris-Euphrates or Mesopotamian basin as a cradle for inland aquatic faunas. A proto-Euphrates collected water from the Levant and had contacts with the Black and Caspian sea drainages before the Pliocene orogeny. Berg (1940) points out that the upper reaches of the Tigris-Euphrates basin today lie on a plateau close to the upper reaches of the Caspian Sea basin. The basin acted as an area where African and Asian species could meet or transit such as the cichlid Iranocichla. These connections were interrupted in the early Pliocene by orogeny, rifting and desert formation. Banarescu (1977) and Por and Dimentman (1989) regard the area to be a zoogeographic crossroads with elements from the Palaearctic such as the cyprinid genera Leuciscus (= Squalius) and Chondrostoma, Mediterranean genera such as the cyprinid Acanthobrama (although Krupp (1987) refers to this genus as Palaearctic, of Mesopotamian origin), and Oriental genera such as the cyprinid Garra and the spiny eel Mastacembelus.

Khalaji-Pirbalouty and Sari (2004) studied the biogeography of amphipods crustaceans in the central Zagros Mountains. They consider habitat diversification and climatic fluctuations to be the principal factors influencing species diversity and endemism in this area, with the mountains acting as a barrier to species distribution. Endemism is evident in lizards, plants and amphipods as well as fish.

An analysis by Coad (1996f) shows that this basin is mainly Black-Caspian sea basin in its connections, with minor links to Asia and possibly Africa. Numbers of families, genera and species shared between the Tigris-Euphrates and neighbouring basins are summarised in this analysis. Relatively few taxa appear to have made the transition between Asia and Africa or survived subsequent climatic and habitat changes.

Certain families are absent from the Tigris-Euphrates but are found in the Indus and the Nile (Notopteridae, Schilbeidae, Clariidae, Anabantidae, Channidae). These are assumed to be of Gondwanic origin and are separated today by plate tectonic movements. A representative of the Channidae is found in eastern Iran but this species is at the western limit of its range there. Only two families are shared between the three basins but are not found to the north, Bagridae and Mastacembelidae, and the relationships of the two species in these families are with the Indus (Travers, 1984).

At the generic level, some have dispersed into eastern Iran from the Indus and other eastern basins but have not reached the Tigris-Euphrates basin, presumably for reasons of time or lack of suitable environmental conditions, e.g. Aspidoparia, Crossocheilus, schizothoracines. However two genera have reached the Tigris-Euphrates (Glyptothorax, Barilius) and Howes (1982) considers Cyprinion to be related to the eastern genus Semiplotus. Barilius resembles Indus and other eastern species superficially although its relationships have not been fully worked out. Assuming that these taxa dispersed westward from the Indus and the east, the route must be determined. All but Cyprinion are absent from much of Iran, including the bagrid Mystus and the mastacembelid Mastacembelus referred to at the family level above (Mastacembelus is not found in eastern Iran and hence does not have a continuous range throughout the Orient (pace Travers (1984)). It is unlikely that rivers of the Tigris-Euphrates basin were once tributary to the Indus when sea levels were lower during glaciations as the Gulf of Oman descends to an abyssal plain at 3340 m. I suspect, but cannot prove, that these taxa reached the Tigris-Euphrates basin across the Iranian land mass and subsequently became extinct as desiccation increased. Many of the rivers in southern and eastern Iran today are very small, regularly dry up and some are highly saline. They may be unsuitable for these taxa. Barilius, it should be noted, appears to prefer, in Asia and the Tigris-Euphrates basin, large lowland rivers and its dispersal across Iran is difficult to envisage by headwater capture (the other genera can be found in small streams at higher altitudes as well as lowland rivers). However Berg (1940) suggested that fish dispersal across this region was facilitated by the coastal rivers of Iranian and Pakistani Baluchestan being part of a single river system in the Pliocene, since submerged by subsidence. The presence of Mastacembelus and Barilius in western Iranian basins is attributed to headwater capture and/or colonisation from the Tigris-Euphrates basin when Gulf rivers were tributary to an expanded Tigris-Euphrates basin during lowered sea levels in glacial times. This distribution of these genera is not, therefore, a remnant of the dispersal across Iran from Asia.

At the generic level, only Garra is found from the Indus to the Nile and in the Tigris-Euphrates basin. Menon (1964) suggests that Garra reached the Tigris-Euphrates basin and Africa in two "waves" from Asia, the first wave being in the Miocene to the Tigris-Euphrates basin, the second through southern Arabia to Africa during the Pliocene. Karaman (1971) disputes Menon's Garra waves based on anatomy and zoogeography. Garra presumably dispersed from Asia to Africa via the Tigris-Euphrates basin and the Levant. The apparent continuous distribution of Garra across southern Arabia is not borne out in systematic analyses by Krupp (1983). Garra (and Cyprinion) species of southeastern Arabia are clearly related to southern Iranian species, having crossed the Persian Gulf when it was drained during the Pleistocene and part of an extended Tigris-Euphrates basin. Southwestern Arabian species (and a Barbus species) are a mixture of African and Levantine elements. Krupp (1983) found no evidence in his studies for the Arabian Peninsula serving as a transition area in an exchange of freshwater fishes between Asia and Africa.

Nemacheilus also has a similar wide distribution but is probably polyphyletic and requires a detailed revision to enable adequate zoogeographical analyses to be made. The systematics of loaches in the Middle East is a contentious subject (Por and Dimentman, 1989). The absence of Nemacheilus species from southern Arabia also argues for a dispersal route through the Tigris-Euphrates basin as these cryptic fishes are found today in many small streams throughout Southwest Asia and are unlikely to have been eliminated from southern Arabia through desiccation.

The only Nile (or east African) genus present in the Tigris-Euphrates basin is Barbus. Certain members of this polyphyletic genus in Southwest Asia are characterised by sharing 6 branched anal fin rays, last unbranched dorsal fin ray a smooth spine, large scales, few gill rakers, high dorsal fin ray counts, reduced barbel numbers, compressed body, and other characters which set them apart from European Barbus as a monophyletic group, probably related to east African species (suggested by Banister (1980)). These Barbus species are found from southwestern Arabia (but not southeastern Arabia), through the Levant and the Tigris-Euphrates basin to rivers at the Strait of Hormuz in Iran. They may represent an African element in the fauna of the Tigris-Euphrates and may reflect the route of the cichlid Iranocichla or its ancestor from Africa to the Strait of Hormuz. Bănărescu (1992b) considers African elements in Southwest Asia to be the oldest, of at least Miocene age.

A significant proportion of the families and genera in the Tigris-Euphrates basin is also found in the Black-Caspian sea basin. Such widespread, northern cyprinid genera as Alburnoides, Alburnus, Aspius, Alburnus, Chondrostoma, and Leuciscus (= Squalius) reach their southern limit in the Tigris-Euphrates basin (and neighbouring Iranian basins) suggesting that they reached the Tigris-Euphrates basin from the north.

The presence of Glyptothorax in the Black Sea basin of Anatolia (Coad and Delmastro, 1985) is a recent event through headwater capture from the Tigris-Euphrates basin and thus far is the only example of a clearly-defined Indus genus reaching the Black-Caspian seas basin. It is probably an example, in reverse, of the colonisation of the Tigris-Euphrates basin in recent times from the Black-Caspian seas basin. Headwaters of a number of Tigris-Euphrates basin rivers interdigitate with the upper reaches of Black-Caspian seas basin rivers, e.g. the Aras River of the Caspian Sea and the Kizilirmak of the Black Sea with the Euphrates near Erzurum and Sivas respectively; the Qezel Owzan of the Caspian Sea with Tigris River tributaries. Headwater capture is common in the Zagros Mountains (Oberlander, 1965) and in Anatolia and pluvial conditions in the past would have facilitated fish dispersal. Por and Dimentman (1989) mention direct connections of a proto-Euphrates with Black Sea and Caspian sea fluviatile drainages before the Pliocene orogeny which would serve to allow entry of taxa to the Tigris-Euphrates basin. Direct connections were interrupted by the early Pliocene as orogeny, rifting and desertification took hold. Almaça (1990) has reviewed possible routes for Barbus species into Iran and the Tigris-Euphrates basin from the north via what is now Anatolia and east of the Caspian Sea dating from the early Oligocene. A continuous route for exchange of taxa has been possible since the upper Miocene, almost 12 million years ago. These routes have been variously available down to modern times for Barbus and other taxa as exemplified by some species being in common between the Black-Caspian seas basin while others are distinct but related at the generic level. Bănărescu (1992b) considers that northern or European elements penetrated to the Tigris-Euphrates basin earlier than Asian ones, and that this partially explains their prevalence.

Iranian internal and Gulf basins and the Levant show evident affinities with the Tigris-Euphrates basin. The ichthyogeography of the Levant has been dealt with by Krupp (1987) and will not be reviewed here. Krupp considers that parts of the Levant were colonised separately via branches of the Tigris-Euphrates river system. Iranian basins to the west of the Tigris-Euphrates basin have a very similar fauna to that of the Tigris-Euphrates at the species level. The diversity falls off rapidly with distance (Coad, 1987). Headwater capture in the Zagros Mountains is an evident route for species found in common with the Tigris-Euphrates basin but not in Iranian rivers draining separately to the Gulf. The draining of the Gulf during Pleistocene lowering of sea levels enabled Tigris-Euphrates basin fishes to colonise tributary Iranian rivers now separated by a rise in sea level. The melting of the Laurentide ice sheet and drainage of Lake Agassiz in Canada caused this rise in sea level world-wide, including the shallow Persian Gulf (Perkins, 2002). By about 11,500 years B.P., the Gulf was filled with present shorelines attained shortly before 6000 B.P. and exceeded by 1-2 m (Lambeck, 1996).

Por and Dimentman (1989) regard the Mesopotamian subregion or Tigris-Euphrates basin as one of the most isolated major freshwater areas in the world. However, as Coad (1997f) points out, endemism is only at the species level and diversity is low with only about 52 primary division species in 7 families, 34 species of which are Cyprinidae.

The Zagros Mountains form the western flank of Iran and store water as snow. The higher peaks are snow-capped even in summer. Zard Kuh, for example, reaches 4548 m (32°22'N, 50°04'E). Rivers drain south and west to become tributaries of the Tigris River in Iraq or its confluence with the Euphrates River, the Shatt al Arab (known as the Arvand (= swift) Rud in Iran). The Shatt al Arab has a course of 190 km to the head of the Persian Gulf and is navigable by ocean-going ships. It forms part of the Iran-Iraq border. The origin of the Tigris River is the Hazar Gölü of Elazig (38°41'N, 39°14'E) between the Murat Nehri and the Euphrates. It flows south-east, forming a short section of the border of Syria with Turkey, before entering Iraq to parallel, roughly, the course of the Euphrates River. It is a larger and swifter river than the Euphrates because of its left bank tributaries from Iran. The Tigris is over 1900 km long (1851 km and 2032 km are extremes cited in the literature). It is the 81st river in size in the world. The Tigris-Euphrates basin encompasses 784,500 sq km of which 19% or 146,000 sq km lies in Iran (Gleick (1993) gives 238,500 sq km and 27% for Iran and 884,000 sq km for the whole basin; the Iraqi Government in the same publication gives 378,834 sq km for the Tigris basin alone with Iran's share 28.8%). Iran contributes 7% of the water supply of this immense basin. The Tigris catchment is 166,155 sq km.

The Tigris is an alkaline river (pH 7.8-8.2) with a total hardness of 200-350 mg/l. Water temperatures range from 8.5°C in January to 31.4°C in August. The flow pattern of the Tigris and its tributaries has a sharp peak in April at about 9 billion cu m, falling rapidly to about 1 billion cu m from August to October before beginning to rise again. The water level may fall by as much as 2 m over the summer. Interannual variation in spring flood levels are marked. Approximate streamflows over the past 6000 years are given by Kay and Johnson (1981) based on proxy data from paleoenvironmental sources. They found an increase in streamflow over this period. The southern province of Khuzestan in the Tigris river basin with 9% of Iran's surface area has an estimated 37% of its surface water flow.

The Shatt al Arab is under tidal influence up to 110 km from the mouth. Its waters are therefore strongly mineralised. Salinity varies with distance from the sea. Crops are irrigated by means of the tidal rise which is used to push fresh water into the fields (Harrison, 1942; Gholizadeh, 1963; Gholizadeh and Fatemi, 1969). This has obvious effects for the fish fauna and its composition as well as for increased salinisation of habitats. There are appreciable diurnal and seasonal fluctuations in physico-chemical conditions. Tidal waters probably penetrated far inland through the Holocene as evidenced by faunal remains in boreholes of the Hammar Formation (MacFadyen and Vita-Finzi, 1978). Al-Hassan and Hussain (1985) describe the hydrological parameters affecting the penetration of marine fishes into the Shatt al Arab. Recently an increase in the Tigris River discharge has decreased salinity in the Shatt al Arab: previously marine species were common at Basrah in Iraq but they became rare, Carassius auratus appeared in Basrah fish market and Cyprinus carpio was caught in large numbers down to the estuary (N. A. Hussain, in litt., 1994). Pollution is widespread in the Shatt al Arab from industrial, agricultural and untreated human wastes. Hussain et al. (2001) evaluate environmental degradation in the Iraqi portion of the Shatt Al-Arab and its effects on the fish fauna.

The principal Iranian tributaries of the Tigris River are the Little Zab River (= Zab-e Kuchek) which drains a small stretch of mountains south of Lake Orumiyeh, and the Diyala River (= Sirvan River) which drains the western mountains of Kordestan. The Diyala River is 442 km long. A principal tributary of the Diyala in Iran is the Qeshlaq River which flows through Sanandaj (35°19'N, 47°00'E). Lake Zaribar, Zarivar or Zeribar is a permanent freshwater body with fringing reed beds and extensive marshes lying at 1435 m in the Diyala River drainage just west of Marivan at 35°32'N, 46°08'E. It has an area of 8 sq km and a maximum depth of 6 m and an average depth of 2.5-3.5 m. Reputedly the lake is fed by 600-700 springs. At high water it overflows into a small river at its southern end. In winter it often freezes over. It was damaged in the Iran-Iraq War suffering rocket and missile hits and chemical warfare (Scott, 1995; 1997). There is a small resort at the southeast corner of the lake, the surrounding land has livestock grazing and agriculture with drainage channels for the peripheral marshes, forests are cut for fuel, and there is waterfowl hunting and fishing. Exotic fish species have been introduced by a government organization, including Alburnus alburnus, Ctenopharyngodon idella, Cyprinus carpio (in two varieties), Hypophthalmichthys molitrix, H. nobilis, Pseudorasbora parva and Gambusia holbrooki. Native fish include Capoeta buhsei (sic),Leuciscus (= Squalius) cephalus and Mastacembelus mastacembelus (Scott, 1997). Jalali et al. (2002) add the species Capoeta damascina (probably the correct identification of the C. buhsei listed above), Carassius auratus and Chalcalburnus (= Alburnus) sp.

A number of minor streams also cross the Iran-Iraq border, but the principal rivers drain through anticlines in spectacular gorges or tangs, funnelling the waters of the Zagros onto the Khuzestan plains through a narrow gap near Dezful (32°23'N, 48°24'E). Stream flows in late winter are at least ten times that of summer and 116,500 sq km of mountains and three big rivers debouch onto 38,800 sq km of plain. Lowlands may be inundated for more than 100 days. Early accounts of floods in Mesopotamia, dating back to Sumerian times almost 5000 years ago, are discussed by Mallowan (1964). Floods can encompass close to 100,000 sq km in Iran and Iraq at the head of the Persian Gulf (Naff and Matson, 1984). Progressive clearing of woodland over the last 7000 years increased runoff, causing higher and more severe floods, soil erosion, increased turbidity in streams and higher sedimentation (Wagstaff, 1985). Erosion is three times the world standard rate at 30 tonnes/hectare and will rise twofold over the next ten years (IRNA, 20 December 1998). All these must have, and continue, to affect the fishes in this and other basins, favouring those species able to cope with these conditions. Even artificial habitats such as small dam reservoirs in Chahar Mahall and Bakhtiari are affected by high sedimentation rates and their utility as fish habitat must be affected (Mousavi and Samadi-Boroujeni, 1998).

The main river is the Karun, with a catchment of 67,340 sq km (Naff and Matson, 1984) and a length of 820 km. It now drains to the Shatt al Arab but once drained directly into the Persian Gulf. The Karun is also connected to the Gulf via the Bahmanshir River, paralleling the Shatt al Arab, and enclosing Abadan Island. The Bahmanshir is the only river along the Persian Gulf coast to have a significant fishery. The Karun headwaters are extensive and lie near both the Esfahan and Kor River basins. The environmental conditions in a headwater dam, the Hanna Reservoir, in the Karun basin are described by Esteky (2001), two-thirds of the reservoir being covered by macrophytes. The Dez River is a Karun tributary and is 400 km long. The Karkheh River (with the Cherdavel, Kashkan, Qareh Su, Gav Masiab and Simareh in its upper reaches) is 320 km long, but is lost in the Hawr-al-Azim marshes of the Tigris after draining 43,000 sq km. Sutcliffe and Carpenter (1967) described runoff from the Karkheh basin. The Karkheh and Dez flows were depleted by 70% in 2001 during a drought and it was thought that these rivers might dry completely (Foltz, 2002). The marshes along the Karkheh and Dez rivers, with oxbow lakes and riverine forest, are a habitat now rare in southern Iran and Iraq outside protected areas. The severe drought of the year 2000 dried up the natural Dez reservoirs south of Dezful (www.irna.com/newshtm/eng/08130315.htm, IRNA, 29 July 2000). The Karkheh Dam, 20 km northwest of Andimeshk, has a crest 3030 m long, a height of 127 m and is the sixth largest dam in the world with a capacity of 7.8 billion cu m, nearly a third of the total dam capacity for the country. The dam is meant to produce electricity, for fish farming and to control floods and drought (IRNA, 17 April 2001; 19 April 2001; Aftab Yazd, Tehran, 346(18 April 2001, 7 pp.; Sadegi, 2003). The Qareh Su near Kermanshah is about 30 m wide and less than a metre deep at its deepest. The Qareh Su or "black water" derives its name from its transparency over a dark, pebbly bed, distinguishing it from the muddy rivers of the lowlands. The Qareh Su is the Classical Choaspes, the water of which the ancient monarchs of Persia carried with them on their military expeditions for its taste, a superiority confirmed by Buckingham (1829). The Gawshan Dam is located at Kamyaran near Kermanshah on the "Gaweh" River and is scheduled for completion in 2002. The dam will be 136 m high and the complex includes a 19 km long tunnel for water transfer (http://netiran.com/news/IranNews/html/94111305INEC.html). Other dams include the 40 million cu m Zarivar Dam in Marivan and the 563 million cu m Kavoshan Dam 35 km south of Sanandaj (http://netiran.com/news/TehranTimes/html/95111803TTPL.html).

Partow (2001) lists 18 dams in the Tigris basin of Iran, either constructed or planned, and these will affect the environment markedly in changing flow regimes, impounding water and eliminating fluvial habitat, removing silt, affecting temperature downstream, causing salinisation as return water from irrigation projects flows back into rivers, and so on. The Karkheh Dam is planned to carry water via pipeline over land (330 km in length) and under the sea (210 km) to Kuwait. The supply rate would be 200 million gallons per day (Partow, 2001) or 300 million cu m (www.irna.com, downloaded 29 January 2003).

The Dez (formerly Mohammed Reza Shah Pahlavi) Dam on the Dez River at 32°38'N, 48°28'E contains 3350 million cu m of water (another source states 60 billion cu m) and has a maximum surface area of 4000 ha. Surface water temperatures can exceed 30°C while at 50 m plus depths it is 15-16°C in summer. Its original life span was estimated at 100 years but this had to be reduced to less than 50 years because of the rapid accumulation of sediment from erosion. Sediment prevents development of a bottom fauna and steep banks with water fluctuations limit vegetation. Nümann (1966, 1969) gives some limnological information on this reservoir. Nümann (1966) recommended introduction of Acanthobrama terraesanctae and Tilapia galilaea from Israel to the reservoir, and later Sander lucioperca and even trout. Sabzalizadeh (2006) gives a description of the ecology of this reservoir and Eskandary et al. (2007) a description of fish populations. Capoeta trutta, Barbus grypus and Barbus esocinus were the most numerous species and the fauna includes the exotics, Carassius auratus, Hypophthalmichthys molitrix and Oncorhynchus mykiss. There is also a diversion dam, the Sadd-e Gotvand. The Gotvand Dam is under construction and will be 180 m high with a reservoir capacity of 4,500 million cubic metres making it the second largest dam in Iran (sic) (IRNA, 25 January 2000). The 205 m high Karun-3 Dam near Izeh, to be completed in the year 2001 (filling actually started in 2003 - www.netiran.com, downloaded 15 November 2004), is a major hydroelectrical plant as is the Karun-4 Dam (Shahid Abbaspour) near 25 km northeast of Masjed-e Soleyman (http://netiran.com/news/IranNews/html/95040822INPL.html). A major dam is also planned at Shushtar (IRNA, 26 September 1998). A tunnel is planned from the Dez River to Golpayegan to supply water to Markazi Province in central Iran (www.iranmania.com, downloaded 19 January 2004).

Some literature refers to the Seymarreh-Karasu-Gamasiab (and variant spellings) as an important complex of rivers. These are the Simareh, Qareh Su and Gav Masiab in gazetteers. A giant dam is planned for the Simareh (IRNA, 26 September 1998). Nümann (1966) notes pollution in these rivers from an oil refinery and sugar factory which decreased fish populations, a condition exacerbated through the use of explosives, insecticides and herbicides by local people to catch fish. He also lists explosive usage on the rivers Khairabad and Zohreh.

Lake Mirabad lies in the basin of the Karkheh at 33°05'N, 47°43'E. While it measures only 100 by 200 m it is important for establishing past vegetation and environments based on sediment cores (Griffiths et al., 2001). The Hashelan or Hashilan Marsh at 34°33'N, 46°55'E occupies 260 to 400 ha (accounts differ) northwest of Kermanshah at about 1310 m. It is a complex of permanent spring-fed pools and associated marshes with much submerged, floating and emergent vegetation. The surrounding plains are heavily grazed and cultivated and ducks are hunted in the marshes. The Sabz Ali spring feeding the marsh has an average annual discharge of 323.4 l/sec, range 208.3-442.5 l/sec, highest in March and lowest in September. The total average volume of water in the marsh is estimated at 1.02 x 10⁷ (Karami et al., 2001). Local people and those from Kermanshah fish in the marsh.

A truck carrying diethyl hexanoyl plunged into the Kashkan River, a Karkheh tributary in Lorestan, 15 km from Pol-e Dokhtar resulting in the poisoning of thousands of fish on 13 April 1998 (IRNA, 14 April 1998; Brief on Iran, 880, 16 April 1998). The river suffered an oil slick in October 2001 when the Khuzestan-Tehran pipeline fractured 4 km from Pol-e Dokhtar. Oil pollution caused a fish kill numbering about 70,000 fish in the Kambel River near Gachsaran, a centre of oil production (Tehran Times, 24 November 2002). Varkouhi and Sobhani (2005) studied the presence of various pollutants in the livers of fishes in the Khorramabad River.

The Jarrahi River is a southern Karun tributary from the east. The Marun River is a major Jarrahi tributary. The Marun and Jarrahi feed the Shadegan Marshes, the largest Iranian wetland according to Kurdistani and Bajestan (2004). The Marun Reservoir Dam northeast of Behbahan was scheduled for completion in 1996 with a crest of 345 m (IRNA, 11 November 1998) but was to be completed in 2004 with a crest of 175 m and containing 1.2-1.3 billion cu m of water (IRNA, 12 January 1999; IRNA, 5 February 2002). There are also four diversion dams on the Marun and one of these, the Jazaeen, has a fishway but fish are trapped downstream of it during their migration (sic)(Kurdistani and Bajestan, 2004). Other dams in this system lack a fishway. Later Kurdistani and Bajestan state that there are no migratory fishes in the Marun, only resident species (which presumably undergo local movements blocked by dams). They mention Barbus grypus and B. pectoralis as the affected species. The Jareh Dam on the Zard River northeast of Ramhormoz dates back to the Sassanid era and is still in use (IRNA, 26 June 2000).

The Karun has the greatest mean discharge, followed by the Dez and Karkheh. The Karun mean discharge is the largest in Iran. The Karun carries a heavy silt load with a hundredfold increase during flood. The Karun discharge ranges from 207 cu m per second to 2225 cu m/sec, average 1100 cu m/sec, while the Dez is 63-1227 cu m/sec, average 288 cu m/sec. The Jarrahi range is 8-770 cu m/sec, average 78 cu m/sec. These figures vary among different sources indicating fluctuations between years and gauging stations; however the relative importance of these rivers is shown. The peak discharge of the Karun is in April, with high values also in March and May; the lowest discharge is in October when flow is only about a ninth of the peak. The combined Tigris-Euphrates-Karun in flood carries five times the load of the Nile (Fisher, 1968). Most of this is deposited north of Basrah (30°30'N, 47°47'E) and much is lost to evaporation in the marshes, e.g. of 27 cu km of discharge into the Persian Gulf through the Shatt al Arab, 22 cu km is from the Karun River. 22 million metric tons of dissolved chemicals are deposited each year and hence there are siltation and salinity problems in the lower parts of this basin.

The Karun River on the Khuzestan plains was examined in 1992 for various parameters and at various localities (courtesy of the Iranian Fisheries Research and Training Organization, Ahvaz). It has a pH of 7.07-8.85, mean 8.17, dissolved oxygen 5.6-12.38 p.p.m., mean 9.29 p.p.m., bicarbonate 79.3-214.72 p.p.m., mean 154.4 p.p.m., carbonate 0.6-21, mean 5.53 p.p.m., total alkalinity 1.9-3.8 meq/l, mean 2.84 meq/l, carbonate hardness 5.32-10.64 p.p.m., mean 7.95 p.p.m., total hardness 168-474 p.p.m., mean 287 p.p.m., ash residue 40-1142 p.p.m., mean 425 p.p.m., chloride 45.4-518.3 p.p.m., mean 207.28 p.p.m., total dissolved solids 226-1374 p.p.m., mean 696 p.p.m., sulphate 43.75-325 p.p.m., mean 101.73 p.p.m., calcium 33.63-101.7 p.p.m., mean 61.8 p.p.m., magnesium 16.8-78.24 p.p.m., mean 33.8 p.p.m., phosphate 0.05-4 p.p.m., mean 0.24 p.p.m., iron trace to 0.32 p.p.m., mean 0.069 p.p.m., manganese trace to 0.657 p.p.m., mean 0.483 p.p.m., and nitrate trace to 0.657 p.p.m., mean 0.039 p.p.m. Esmaili et al. (1999) report heavy metals in water, sediments and fish from the Karun River and Jafarzadeh-Haghiehi et al. (2005) report on the poor water quality of the river.

As lowlands at the head of the Persian Gulf receive waters from this vast drainage basin, floods occur, increasing the depth and extent of marshes. Flood waters may increase depths by 1-1.5 m, with 2-3.5 m in more permanent basins. Most of the large marshes lie in Iraq, but the Hoveyzeh or Hawr-al-Azim marshes are on the border, and occupy 3000 sq km at high water. They are fed by the Karkheh and other rivers from Iran. Construction of the Karkheh Dam in Iran (and pipeline water transfer to Kuwait) will reduce input of water to this marsh, compounded by canal construction and draining of marshes in Iraq. Additionally, irrigation return waters will be salinised (Partow, 2001). A dam has been built by Iran across the Hoveyzeh marsh to retain water on the border with Iraq. Marsh temperatures range from 15°C in January to 31°C in August and fish may retreat to deeper areas or move upriver at the higher temperatures. Flooded marshes tend to be warmer than rivers in winter. The Shatt al Arab has temperatures of 32°C in July and 16°C in December.

Floods are often a feature of these southern rivers and some loss of fish stocks must occur as they recede. For example, the Jarrahi and Zohreh rivers overran their banks in November 1994 after torrential rains causing widespread flooding (http://netiran.com/news/IranNews/html/94112109INEV.html).

The Zagros Mountains consists of tightly packed ranges in the Tigris basin trending north-west to south-east. A trellis drainage pattern is imposed on this. The tangs, their formation and the drainage pattern are described by Harrison (1937) and Oberlander (1965; 1968a). These deep defiles may exceed 2400 m in depth with vertical walls of 300 m splitting anticlinal mountain ranges instead of taking apparently easier routes around their ends. They may well be barriers to the movement of less vagile fish species or a highway into the interior for those with some dispersal ability. Tangs formed because an antecedent drainage over lower relief was gradually uplifted at a rate slow enough to permit streams to cut through ridges and retain the original pattern of drainage once the softer material was washed out of the valleys between the anticlines.

The uppermost parts of the basin show evidence of headwater captures and this orogenic zone is very unstable. The divide between endo- and exo-rheic basins is not the snowline of the Zagros but is east of it, so streams must first cross the Zagros peaks to start on their journey to the Persian Gulf.

Springs are important in the mountains, tapping aquifers and helping to maintain river flow. The Karun River traditionally has its source in springs. Keivany et al. (1992) surveyed 72 springs in Chahar Mahall va Bakhtiari Province, in the upper Karun River basin, and found them suitable for trout culture with a potential production of about 6000 tonnes per year. Flows varied from 50 to 4000 l/second, temperature from 6 to 15°C, pH from 6.2 to 7.8, conductivity from 128 to 570 mMoh/cm, total alkalinity from 20-220 meq/l, total hardness from 140-250 mg/l, oxygen from 7 to 11 mg/l, carbon dioxide from 5 to 20 mg/l (falling rapidly to less than 2 mg/l within a few tens of metres of the spring source), H₂S 0 mg/l, Cl^- 1-28 mg/l, SO₄^-- 14-135 mg/l, PO₄^-- 0.1-0.3 mg/l, Ca⁺⁺ 16-82 mg/l, Mg⁺⁺ 3-34 mg/l, K⁺ 0.2-1.0 mg/l, Na⁺ 0.5-1.5 mg/l, Fe⁺⁺⁺ 0-0.06 mg/l, Fe⁺⁺ 0 mg/l, NO₂^- 0-0.2 mg/l, NO₃^- 0-13 mg/l, NH₄⁺ 0-0.5 mg/l, and HCO₃^- 48-220 mg/l. Springs (or sarabs) in Kermanshah Province have been described by Khatami and Shayegan (2003) and are regarded as a significant water supply for rivers. Sarabs are used for drinking water and irrigation, and are threatened by pollution and fish farms. Qanats are also found, in drier parts of the basin, but they are not as significant for fish habitat as in other parts of Iran.

Marshes and ponds as well as seasonally flooded arable land along the Karun River in the lowlands of Khuzestan provide temporary and permanent habitats for fishes. Some are reviewed below.

The "Hawr-e Bmdej"? or "Sadi Shavour" Marshes lie between the Karkheh and Dez rivers northwest of Ahvaz at 31°45'N, 48°36'E and encompass 12,000 ha. This is the most extensive permanent freshwater marsh with tall reeds of Phragmites and Typha in Khuzestan. There is relatively little open water. Some parts are being drained for agriculture, a continuing trend for marshes with concomitant loss of fish habitat. The "Hamidieh" plains at 31°20'N, 48°20'E comprise 20,000 ha of seasonally flooded (winter) plain and arable land along the Karkheh River. Hamidieh Lake, an old oxbow of the Karkheh, is included in this area and is permanent fresh water. The lake is 3 ha and has extensive reed beds.

The "Susangerd" Marshes or Hawr-e Susangerd at 31°45'N, 47°55'E are northwest of Ahvaz near the Iraqi border and form the extreme eastern edge of the Hawr-al-Azim, most of which lies in Iraq. The marshes occupy about 30,000 ha and are made up of permanent and seasonal fresh and brackish marshes and seasonally flooded arable land. The marshes are on the floodplain of the Karkheh River. Irrigation projects, grazing by livestock, reed cutting and fishing all occur here. Parts of the marsh were damaged by the Iran-Iraq War. The Iran-Iraq marshes declined in area from 1089 sq km to 758 sq km from 2000 to 2002 and was predicted to dry up in 5 years from 2002 because of the Karkheh Dam. Reports conflict since once the dam was full, a relatively normal flow regime would help maintain the marshes. Restocking with 490,000 Barbus sharpeyi and and B. xanthopterus took place in this marsh (www.shilat.com, downloaded 12May 2006).

The Shadegan Marshes at 30°20'N, 48°20'E occupy 282,500 ha (Jones, www.ramsar.org/lib_dir_2_3.htm, downloaded 4 April 2000) gives 296,000 ha) and form the southern part of the seasonal floodplain of the Dez, Karun and other rivers at the head of the Persian Gulf. There are adjacent tidal mudflats. The central and southern part of the marshes are part of a Ramsar Site, along with the mudflats (World Conservation Monitoring Centre, 1990). Sabzalizadeh and Amirineia (2003) give some physical and chemical characteristics of 5 sample stations in this marsh. Range of pH was 7.2-9.4, maximum water temperatures occurred in July and August. Maximum levels of dissolved oxygen were found in November and February but were more than 5 p.p.m in most cases, optimum for fish growth and reproduction. The water quality was hard and brackish. The whole area may dry out in late summer, a natural condition exacerbated by dams and irrigation schemes on the major inflowing rivers. In a November 2000 visit, much of this area was dry although it had been flooded in 1999. When the marsh dries, fish concentrate in the deeper pools where they are easily caught, even the smaller ones. The marsh is re-colonised from the rivers. The fishes of this marsh in order of abundance are kopur, shirbot, touyeni, esbele, binni, berzem, biah and very few himri and gattan (Y. Mayahi, pers. comm., 2000). Rice paddies occupy part of the Ramsar Site and reed cutting, fishing and grazing goes on. There is extensive reed cutting, some livestock grazing, some rice paddies and potential pollution from main roads, shipping and oil terminals. Over 100,000 ha were contaminated with oil from a leaking pipeline in 2000 and 35,000 cu m of refinery wastes were dumped in the marsh in 2004 (www.payvand.com, downloaded, 5 September 2006). Chemical weapon use occurred here in the Iran-Iraq War and acid rain fell from the burning of the Kuwaiti oilfields in the Gulf War. About 10% of the marshes were destroyed (Anonymous, 1988b; Scott, 1993; Jones, www.ramsar.org/lib_dir_2_3.htm, downloaded 4 April 2000). Fishing is important. The Shadegan Wildlife Refuge, encompassing 296,000 ha, is on the threatened list for National Parks since it was substantially damaged in the Iran-Iraq War, both physically and by chemical agents.

The principal fishes appearing on fish stalls in Ahvaz from marshes such as Shadegan are Barbus xanthopterus, Liza abu, Barbus sharpeyi and Cyprinus carpio as well as cultured Hypophthalmichthys molitrix as escapes or plantings. Farm ponds in Khuzestan have Barbus barbulus, Ctenopharyngodon idella, Hypophthalmichthys molitrix and Cyprinus carpio. Hawr-al-Azim, Hawr-al-Hoveyzeh and the Shadegan marshes are important refuges for fishes in Khuzestan (Korki, 1992; N. Najafpour, pers. comm., 1995). 490,000 fingerlings of Barbus sharpeyi and B. xanthopterus were stocked in this marsh in 2005, a 40% increase over the previous year (www.iranfisheries.net, downloaded 30 November 2005).

Izeh and "Shiekho" lakes at 31°52'N, 49°54'E occupy 1400 ha in the Zagros foothills. These small freshwater lakes are shallow with extensive sedge marshes. Izeh is the deeper of the two with much more open water. They are fed by runoff and springs. Shiekho, the larger lake, is almost overgrown with emergent vegetation except where cattle have grazed and trampled areas leaving some open water. Some fishing occurs in the lakes and water is abstracted for irrigation.

"Choghakor" or "Chaghakhour" Marsh or Wetland at 31°55'N, 50°54'E lies in upper Karun River drainage in the Zagros Mountains in Chahar Mahal va Bakhtiari at ca. 2100-2270 m and occupies 1600 ha. Maximum depth in spring and winter is 2 m but in summer it is almost entirely dry and overgrown with emergent vegetation. Construction of a dam may enable a more permanent marsh to exist (Taqvaie and Ramezani, 2002) although others consider dam construction to be a threat to the habitat and its diversity as the habitat changes from a wetland to a lake (Ebrahimi and Moshari, 2006). After the dam was built, water depth increased from 1.5 m to 6 m or more.

"Gandoman" Marsh at 31°50'N, 51°07'E at 2250 m and occupying 1500 ha (or 1200 ha, Khan et al. (1992) or 3510 ha Taqvaie and Ramezani (2002)) is a similar habitat but it has a stream running through it. "Sulegan" wetland or marsh in the same area encompasses 164 ha and is spring fed. These marshes have been proposed as a Ramsar Site although not yet formally designated (Scott and Smart, 1992).

The southern areas of this basin are areas with high temperatures and large cities (Abadan in Iran and Basrah in Iraq). Adjacent waters are highly polluted with sewage, agricultural waste and other chemicals (e.g. see DouAbul et al., 1988; Diagomanolin et al., 2004; Karamouz et al, 2005; Afkhami et al., 2007). The increased use of motor boats has led to oil pollution. DDT is still sprayed against malarial mosquitos on stagnant pools adjacent to the main river course leaving a brown stain on the rocks (observations in 1995; a letter of complaint to the appropriate agency carrying out this spraying by the Iranian Fisheries Research and Training Organization elicited no response). Scott (1995) records sale of Chloridrin, a persistent insecticide, to residents of the Hawr-al-Hoveyzeh in Iran as a means of poisoning large numbers of fish for sale. Phytoplankton blooms are common and in canals the chlorosity increases, transparency decreases and pH is reduced because of the dying plant material. The Shatt al Arab is more affected by physical factors as it is an estuary. Historical problems with salinisation of soils (and presumably water) extend back 5000 years in southern Mesopotamia including Khuzestan, a consequence of over-irrigation and inadequate drainage (Goldsmith and Hildyard, 1984). The irrigation systems rose and fell with the vicissitudes of history. There was a large-scale irrigation network in Khuzestan during the Sassanian period (A.D. 226-639), lost through conflict and natural disasters after this date and reconstructed in modern times (Adams, 1962).

A theory has been advanced that the silt-laden discharge of the Tigris-Euphrates-Karun rivers has built out a delta into the Persian Gulf. The head of the Gulf would have reached Baghdad and Samarra about 7000-6000 B.P. and since then the land area is supposed to have extended some 200 km southward. The present plains would not then have been as extensive and rivers from Iran would have entered directly into the Gulf. The Admiralty Naval Staff (1918), Mason et al. (1944), Adams (1962), Hansman (1978), Maltby (1994) and Lambeck (1996) provided illustrations of this recession of the head of the Persian Gulf in historic times along with details of historical and archaeological evidence. The sea coast was then supposedly as far inland as Ahvaz in Iran for example. Lees and Falcon (1952) proposed that in fact downwarping occurs under the weight of sediment. Certainly the silt load has not built up a land surface. The coastline, under this theory as interpreted by Fisher (1968), has been constant since the end of the Pliocene and presumably as a marsh habitat for fishes too. However Lees and Falcon did state that there were advances and retreats through historic and prehistoric time. Ionides (1954), Larsen (1975) and Nützel (1975) refuted Lees and Falcon and maintained that marine clays and silts indicate a marine embayment as far inland as Amara in Iraq (31°50'N, 47°09'E) and that the third millennium cities of Ur and Eridu have left cuneiform sources placing them on the sea although now they are 100 km from the head of the Persian Gulf. Lees and Falcon did not take into account sea level changes such as the postglacial rise of 100 m and interglacial rises of 30-100 m. Active growth of a delta at the head of the Gulf over the last 20,000 years may only have occurred from 10,000 to 2000 B.P. and again in the last 300 years. Subsidence levels are probably not as great as postulated (Vita-Finzi, 1978). Nevertheless, there were probably marshes to the north and they may have just become more available and extensive in recent centuries (Aqrawi, 2001). As Larsen and Evans (1978) and Wagstaff (1985) point out, the Persian Gulf shoreline at the head of the Gulf has been affected by, and rendered difficult to interpret by, a complex of factors including confusion of marine and freshwater fossils in an estuarine environment, subsidence, eustatic sea level fluctuations, local seismic activity, climate and therefore hydrologic changes, and cultural changes such as irrigation. Jacobsen (1960) detailed some of the changes in the courses of rivers and canals, based on evidence of ancient settlements which were presumed to be linearly arranged along water courses. Mallowan (1964) also maps some ancient river courses. The fish fauna has evidently had to cope with a changing availability of habitat through the post-glacial period. Floods and changes in river courses over this time have no doubt facilitated movement of fishes between Iran and the Tigris-Euphrates basin. It seems unlikely that the separate entry of rivers from Iran into the Gulf would have led to isolation of the faunas to any significant degree.

Canals and other irrigation structures have long been a feature of the Mesopotamian plains, forming habitats for fishes dating back thousands of years (Bagley, 1976). Their loss through natural and man-made disasters must have affected fish populations but sufficient natural habitat no doubt remained to ensure survival. The construction of dams upstream in Turkey and the large scale, modern drainage programmes in Iraq bordering Iran such as the "Three River Project" are drying up the extensive marsh systems and these are regarded as an eco-disaster leading to desertification in Iraq and adjacent regions of Iran (North, 1993; Pearce, 1993, 2001; Ryan, 1994; National Geographic, 185(4):unnumbered page, 1994; Scott, 1995; Munro and Touron, 1997; Maltby, 1999; Partow, 2001; www.amarappeal.com/documents/Draft_Report.pdf, downloaded 15 November 2001). The 32 km long "Fish Lake" was constructed as a barrier to Iranian attacks on Basrah. The Iranians dug several drainage ditches from "Fish Lake" northeast of Basrah to the Karun River, to dry up land for infantry attacks on Basrah. This whole marsh area of about 17,000 sq km, is the most important wetland in the Middle East and one of the top ten in the world. The Central and Al-Hammar marshes in Iraq by 2001 have had 97% and 94% of their land converted into bare ground and salt crusts. Less than one-third of the Hawr al Hawizeh (= Hawr al Azim in Iran) survives. It was estimated in the 1990s that the marsh area would be a desert within a decade and this seems to be an accurate assessment. The effects on the fishes in Iran are unknown but much habitat is being lost which could have served as a reserve against loss in Iran through natural and man-made changes.

The Iran-Iraq War of 1980-1988 severely damaged the Hawr-al-Hoveyzeh in Iraq, and presumably to some extent in Iran. Bombs and shells, chemical weapons, pollution, burning of reed beds, reed cutting and armoured boats used to smash through obstructing reeds all had deleterious effects (Scott, 1995). The Iraqi shores of this hawr have been drained by dyke construction and river control presumably for military reasons in this border area. Some marsh will survive in Iran because it is fed from wholly Iranian rivers but Iran News (19 February 1995) reports that draining of Iraqi marshes will lead to desertification inside Iran.

The Southeast Anatolia Project (known as GAP after its Turkish acronym) incorporates 21 dams and 19 hydroelectric facilities including the massive Ataturk Dam on the Euphrates completed in 1993. It plans to draw off one-third of the waters originating in Turkey and will also use water from the Tigris River (Ottawa Citizen, 10 November 1994; Morris, 1992; Biswas, 1994; Beaumont, 1998). The reduction in flow for Iraq may reach 60%, especially when water is taken from the Euphrates or ath-Thawrah Dam (its reservoir is Lake Assad) at Tabqa in Syria (Vesiland, 1993). This will have major downstream effects, less so in Iran than in Syria and Iraq, but flow into the Shatt al Arab shared between Iran and Iraq will be greatly decreased perhaps allowing greater penetration of saline water and restricting migrations of fishes.

Between 20 and 15 thousand years ago, the Persian Gulf was dry as water was locked up in ice-caps and sea level was 110-120 m lower than today (Sarnthein, 1972; Kassler, 1973; Nützel, 1975; Al-Sayari and Zötl, 1978; Vita-Finzi, 1978). The floor of the Gulf was then thought to be a generally waterless, flat depression with a few swampy tracts rather than a "Garden of Eden" as has been proposed. A marine transgression occurred between 12 to 8 thousand years ago and by 6 thousand years ago the present sea-level was attained. Streams now isolated from the Tigris River basin by the sea in the Gulf and Hormozgan basins would have been tributary to an extended Shatt al Arab, extending 800 km down the gulf to form an estuary at the shelf margin in the Sea of Oman, now under 110 m of sea. Earlier regressions no doubt occurred and facilitated the movement of fishes.

Construction of fish farms is widespread throughout this basin in Iran. For example in Lorestan Province, 772 tonnes were produced by the Lorestan Province Fishery Company in 1997, 50 fish farms were under construction and 125 pools built for aquaculture uses. The long-term aim was to increase fish production to 20,000 tonnes worth 156 billion rials and employing 10,000 people (Tehran Times, 22 September 1998). In Chahar Mahall va Bakhtiari Province in the highlands of this basin, 4360 tons of trout fingerlings were produced with plans to produce 8000 tons in future years (Tehran Times, 14 March 2005).

Berg (1940) places this basin in the Mesopotamian Transitional Region, since the boundaries of three zoogeographical regions meet here, namely the Holarctic (i.e. its Palaearctic part), Sino-Indian (= Oriental) and the African (= Ethiopian). The Mesopotamian Transitional Region includes the Tigris and Euphrates basins and the Quwayq River, Syria, forming a single Mesopotamian Province. The province is transitional between the Mediterranean Subregion and the Indian Subregion. Genera such as Leuciscus (= Squalius) Aspius, Chondrostoma and Alburnus point to a Mediterranean or European association while such genera as Glyptothorax, Barilius, Mystus and Mastacembelus point to an Indian association.

Endorheic Basins

Bejestan Highland

This basin comprises the drainages of the eastern highlands north of Birjand (32°53'N, 59°13'E) flanked by the Kavir basin to the west, the Lut and Sistan basins to the south, the Tedzhen to the north and the Afghan border to the east. The Tedzhen basin is separated by three ranges, from west to east, the Kuh-e Sorkh (35°30'N, 58°36'E) at 3017 m, the Kuh-e Bizak (35°11'N, 60°20'E) and the Kuh-e Khvaf at 2517 m east of Khvaf (34°33'N, 60°08'E). These receive snow in winter from moist Caspian Sea air. The highlands are relatively low compared with other parts of Iran and nowhere exceed 3000 m except for the Kuh-e Sorkh. The lowest points are in the sumps on the Afghan border at about 610 m. There are a number of minor sumps and the drainage patterns have been described as indeterminate. The total area is about 82,000 sq km. Tectonism commonly causes drainage disruptions (Krinsley, 1970).

The distinction of the western parts of the basin from the Kavir basin is somewhat arbitrary since the Kavir-e Namak near Bejestan (34°31'N, 58°10'E) lies at a similar level to the Kavir-e Bozorg and is separated by only a low rise in the land. This kavir receives intermittent streams from the east and north. The Bejestan basin does receive tributaries from Afghanistan but these are minor and do not begin to approach the input received by the Sistan and Tedzhen basins from the east. Streams drain mostly to the east, to three small terminal basins straddling the border; from north to south these are the Namakzar-e Khvaf, the Daqq-e Patargan and the Daqq-e Tondi.

The Lut basin to the south is separated by the drainage divide of the Birjand-Qa'in highlands, which trend north-west to south-east. Kuh-e Kalat is at 2605 m (34°18'N, 58°22'E) in the north-west and altitudes of 2779 m are reached in the south-east.

This whole basin has seasonal streams and a few springs with qanats a prominent feature. Water temperatures in qanats is 22-25°C year round and their is little fluctuation in water flow and chemical composition. Springs in contrast are influenced by the local geology and have a variable chemical composition, as well as being influenced by climate and pollution (Ruttner-Kolisko, 1964; 1966).

Caspian Sea

The Caspian Sea (Darya-ye Khazar, Darya-ye Mazandaran) basin is here taken to include both the rivers draining to that sea and the sea itself within Iranian territorial waters. This basin, in its land part, is elongate, extending from the Turkish border almost to the Afghan border and only acquires some width where the Safid River and its tributaries penetrate the Alborz Mountains in the west. According to Pirnia (1951) the Caspian basin in Iran (excluding the sea) encompasses 182,100 sq km while according to Zakeri (1997) this figure is 256,000 sq km, 15.5% of the whole country. Zakeri (1997) records 864 small and large rivers, including the Safid River with a catchment of 67,000 sq km. Much of the information on the Caspian Sea itself is restricted to waters of the former U.S.S.R. and there is relatively little on Iranian territorial waters. Rozengurt and Hedgpeth (1989), Kosarev and Yablonskaya (1994), Mandych (1995) and Golubev (1996) summarise much of the recent Soviet literature and a general review is given by Mamaev (2002).

An ongoing and developing source of information on this sea, the surrounding land, its history, its management, biodiversity strategy and action plan, and a wide sweep of environmental problems is the Caspian Environment Programme (CEP), Baku, Azerbaijan at www.caspianenvironment.org. This site has numerous documents and reports on-line, some with authors, e.g. Katunin (2000), Ivanov and Katunin (2001), ERM-Lahmeyer International GmbH, DHI Water & Environment and GOPA Consultants (2001a), others appearing under CEP or TACIS (Technical Assistance to the Commonwealth of Independent States, European Union), e.g. TACIS and UNDP (2000), TACIS (2002), CEP (1998, 2000b, 2002). These reports include information on the fishes and fisheries but are best referred to for the interactions between people and the environment. Kiabi et al. (1999) describe the wetlands and rivers of Golestan Province at the southeast corner of the Caspian Sea. Razavi (1999) gives an introduction to the ecology of the sea in Farsi. Nezami et al. (2000) and CEP (2001) give recent general descriptions of the Iranian Caspian coastal zone, the important rivers, wetlands, water quality, climate, pollutants, and fisheries. www.bibliothecapersica.com/articlenavigation/index.html, under Caspian Sea, downloaded 24 December 2004 also gives an overview of this basin. Nadim et al. (2006) review the management of coastal areas in the Caspian Sea.

The Caspian Sea is the largest "lake" or inland water body in the world at 436,284 sq km, a surface area encompassing 18% of the total area of all lakes in the world, about the same area as Great Britain (other surface area figures are 378,400 sq km, 384,400 sq km and 390,000 sq km - data of this nature varies quite markedly between apparently authoritative sources). The volume is 78,100 cu km, 44% of the total volume of inland lakes of the world. Its north-south extent is 1204 km and width is 204 to 566 km. The shoreline, including islands, extends for 7000 km, 1000 km of which is Iranian. The catchment area is 3.6 million sq km. Dumont (1998) presents arguments for this water body being a true lake and not a sea.

North, Middle and South Caspian basins are recognised, divided by shoals. Iranian waters fall within the South Caspian Basin which occupies 148,700 sq km and is separated from the Middle Caspian by the Apsheron Bank. The South Caspian holds over 65% of the sea's water and is the deepest basin, to -1000 m in depressions, average - 325 m. The northern basin holds only 1% of the water.

The sea receives 291 cu km from river run-off and 87 cu km from precipitation but loses 374 cu km from evaporation and 11 cu km to overflow into the Kara Bogaz Gol (Gerasimov, 1978b). The Volga River accounts for 76.3% (82% according to Dumont (1995)) of the inflow of rivers, the Kura River 4.9%, the Ural River 3.7%, the Terek River 3.2% and the remaining rivers including all those of the Iranian shore 11.9%. Iranian rivers account for only 5% of the Caspian inflow, Iran has 7% of the catchment area, 14% of the coast, contributes 3% of the settling solids, and 2% of the fishery (Badakhshan and Shayegan in Glantz and Zonn, 1997). The Volga has its headwaters near Moscow and is 3688 km long with a catchment area of 1,360,000 sq km and a mean annual flow at Volgograd of 8380 cu m/sec. The Volga is of prime importance in the Caspian Sea basin to migratory fishes as a spawning site and the biology of these species has been studied extensively. Often these studies provide the basis for much of the knowledge of Iranian fishes to the south.

Zenkevi(t)ch (1957; 1963) and Barimani (1977) have reviewed the geography, hydrology and biology of the Caspian Sea, Moiseev (1971) summarises the living resources of the whole sea, Karpinsky (1992) aspects of the benthic ecosystem, and Knipovich (1921), Il'in (1927a), and Nevraev (1929) give accounts of Iranian coastal waters and regional fisheries in the early twentieth century. Zahmatkesh (1993) describes the gammarids and bottom sediments, Fallahi (1993) the plankton and Soleimani (1994) the benthic fauna in Iranian waters. Mamaev (2002) is a recent general overview.

Water balance for this sea depends on a delicate balance of inflow, evaporation, precipitation, climate, and abstraction for human needs. Water 10 m deep or shallower has a bottom of sand and gravel while at greater depths of 50-100 m clay and softer sediments increase. There is more sand in these greater depths off Gilan compared with off Mazandaran.

Maximum depth is 1025 m, mean depth is 184 m, and depth below sea level is -28 m (-27.66 m averaged over the past 2,500 years according to Dumont (1998)). There are natural water level fluctuations - the figure cited is from 1983; in 1978 it was -29.02 m, the lowest recorded since observations began (Voropaev and Velikanov, 1985). Petr (1987) has pointed out that a decline below -28.5 m would result in a change in salinity distribution and in water currents mixing riverine and sea water. A decline in productivity would follow. A fall of only 1 m would cause a 60% reduction in fish food supply and, since this fall poses barriers to migration to better feeding grounds, a further 20% loss in food supply. Recently however, since 1978, the sea has begun to rise, by 2.1 m from 1978 to 1993 to -26.95 m, with a possible rise of 3 m in the next 25 years. Vaziri and Borghei (1995) give an average rise of 1.2 cm a month for the period 1986-1993. The sea rose 26 cm in 1994. However, over the past 2500 years the sea level has not exceeded -25 m and is not anticipated to do so in the near future; the level is cyclical (Rychagov, 1997; Gorji-Bandpy and Hooman, 2004). The reason for the rise is probably a climatic shift (Mandych, 1995; Shayegan and Badakshan, 1996; Kobori and Glantz, 1998) but a sheen of oil from pollution may be helping in the reduced evaporation of 7-10% observed over two decades. Tectonic shifts of the sea floor may also be a contributing factor. Predictions of water level changes have proved unreliable so schemes to ameliorate rises or falls are unwarranted and could be catastrophic (Abuzyarov, 1999). Georgievskiy (2001) however, predicts a lowering of the sea level to -27.6-28.9 m by the year 2030 from -27.0 m in 2000. Klige and Myagkov (1992) examined the water balance of the Caspian Sea and predicted a rise in sea level to 1995-1997 and then future declines of the order of several metres in the next century.

The rise in water level is engulfing buildings including industrial sites which will pollute the waters of the Caspian further. Iranian towns and cities damaged include Babolsar, Tonekabon, Ramsar, Ashuradeh, Bandar-e Torkoman, Anzali, Astara and Kolachai (Zonn in Glantz and Zonn (1997)). Fish caught near Nowshahr in 1999 were contaminated with oil pollutants (Tehran Times, 1 November 1999). The complex of chemical, petrochemical and metallurgical plants at Sumgait near Baku in Azerbaijan produces 335,000 tonnes of mostly toxic waste including dioxins. Hundreds of waste lakes of oil near Baku are being slowly engulfed by the rising Caspian. Nasrolazadeh Saravi (2001) and Khatoonabadai and Dehcheshmeh (2006) describe oil pollution in Iranian coastal waters although it is much less than near Baku, particularly in Mazandaran and Golestan. Heavy metals enter down the major rivers from mining and industry and the effects from the Kura River may have rendered the coast of Azerbaijan almost untenable for life (Bickham, 1996; Pohlman and Naismith, 1996; Rowe, 1996). Radioactive waste, both liquid and solid, is found in low lying depressions around nuclear power plants and is liable to enter the Caspian (Rodionov, 1994; Dumont, 1995).

On the plus side, sturgeons may benefit from easier access to spawning grounds (Ottawa Citizen, 9 July 1994; 3 July 1995) but this is probably offset by the pollution load of the major spawning rivers.

In contrast to the recent rise in sea level, a series of reports have appeared in past scientific and popular literature on the falling level of the Caspian Sea and diversionary schemes to combat this (e.g. Kovda, 1961; Lamb, 1977; Hollis, 1978; Gribbin, 1979; Micklin, 1979; 1986; Golden, 1982; Rich, 1982; 1983; Voropaev and Kosarev, 1982; Voropaev and Velikanov, 1985; Pearce, 1984; Ryan, 1986; Perera, 1989; Rozengurt and Hedgpeth, 1989; among others). The Caspian dropped 2.3 m between 1930 and 1962 and area has decreased by 10% or 40,000 sq km. Recent historical levels appear to be between -25 and -26 m, average -25.8 m. Changes in level of the Caspian due to natural or other causes in historical and pre-historical times have been reviewed above. Fall in the sea level increases salinity, destroys habitat and blocks spawning migrations, although some effects are less in the southern, Iranian Caspian because of the larger water mass. The Volga accounts for 76% (some reports say more than 80%) of the river input to the Caspian Sea. The Volga is now extensively dammed, as are other rivers in this basin, and its waters used for industry and agriculture. There are 8 large dams on the Volga, the largest being the Kuibyshevskaya with a reservoir area of 6450 sq km and a total volume of 58 cu km. Dams in the Caspian basin provide almost one third of the hydropower of the former U.S.S.R. (Rozengurt and Hedgpeth, 1989). Flow into the Caspian has been cut by at least 25% and in spring, the time of spawning migrations, by as much as 37% for the Volga-Kama systems. Berka (1990) reviewed the effects of water level changes on the northern Caspian fisheries. The North Caspian was designated as an "ecological disaster area" in 1992 because of water pollution input from the Volga. The delta is eutrophic with cyanobacterial blooms being common, affecting fish survival (Saiko in Glantz and Zonn, 1997).

The decline in sea level has been reversed in recent years and a rise of nearly 2 m was reported and, in Turkmenistan, a shoreline advance of 2-3 km in places (Rich, 1991; Anonymous, 1992a; Golub, 1992; Ottawa Citizen, 9 July 1994; Priroda, 5:3-25, 1994). This will have positive effects for some fisheries and wetland conservation but negative effects on recent, low-lying construction including oil refineries and wells in Azerbaijan and a nuclear waste dump in Turkmenistan which would cause massive pollution from oil and radioactive compounds (Pearce, 1995). Environmental hazards to the fisheries caused by sea level rise include eutrophication from farmland covered by the sea, pesticides and herbicides from inundated farmland, salt water penetration into wetlands, input of solid municipal and industrial wastes and vegetation, destruction of fish habitat, and input of soil altering the ecosystem (Shayegan and Badakhshan in Glantz and Zonn, 1997).

It has been suggested that the rise in sea level is due, in part, to seepage from the Aral Sea basin and that this could be halted by setting off underground explosions. This smacks of the large-scale alteration to the environment favoured by Soviet planners to combat the fall in sea level - both are grandiose and have unknown consequences for the environment. Climate change is probably a major factor abetted by the closing off of the Kara Bogaz Gol (responsible for an estimated 40-45 cm rise alone) and diversion of Siberian rivers into the Ural River in the northeastern Caspian (Khan et al., 1992).

Much of the former southern U.S.S.R. is water poor and a solution to this and the falling Caspian level has been advocated. This would involve diversion of north flowing Siberian rivers at a cost $40 billion. The potential for environmental damage on a local and even global scale caused this scheme to be shelved in 1986. The project involved excavations using nuclear explosives, drowning of forests and construction of canals thousands of kilometres long. Reduced flow into the Arctic Ocean could affect ice cover which influences atmospheric pressure and circulation patterns over the whole northern hemisphere. This Soviet plan has recently been revived (Pearce, 2004).

There is an abundance of historical and other evidence for variations in Caspian Sea level and its connections with other water bodies in both recent times and over several million years (Huntington, 1907; Ehlers, 1971; Lamb, 1977; Gerasimov, 1978b; Hsü, 1978; Coad, 1980c; Rögl and Steininger, 1984; Wossugh-Zamani (1991c); Oosterbroek and Arntzen, 1992; Sal'nikov, 1995; Mamedov, 1997; Rychagov, 1997; Caspian Environmental Programme, 2000; Grigorovich et al., 2003; Kotlík et al., 2008). Brooks (1949) maintains that the Oxus (= Amu Darya) flowed into the Caspian in the 14th century instead of the Aral Sea. Shnitnikov (1969) and Gerasimov (1978a) report flow along the Uzboi channel north of the Iranian border into the Caspian from the Aral Sea basin at several periods from the third millennium B.C. to the 16th century. Sal'nikov (1998) illustrates connections between the Amu Darya and the Caspian Sea from the Pleistocene to the 20th century. The connection between the Caspian and Amu Darya and Aral Sea was interrupted about 20,000 years ago when the Amu Darya turned north, was reconnected about 10,000 years ago, and essentially interrupted about 4000 years ago. These regular contacts have resulted in an Aral Sea ichthyofauna with "weakly pronounced endemics", although the Amu Darya ichthyofauna has a number of clearly defined endemics which are not yet found in the Caspian Sea basin (but see below under Tedzhen River basin). Dunin-Barkovsky (1977) records level fluctuations of up to 50 m during the Holocene due to variations in the general moistening of Eurasia and intermittent warming and cooling variously associated with changes in precipitation and evaporation. Ice melt from the Fennoscandian ice cap, as late as 4000 B.C., added large volumes of water to the Caspian and an overflow to the Black Sea was then possible. Berg (1948-1949) maintains that Atherina presbyter and Syngnathus abaster entered the Caspian at about this time. Some fishes, such as Salmo trutta, are probably immigrants from Arctic regions and certain cyprinoids and percids are freshwater immigrants. Bianco (1990; 1995b) points out that, at every glacial- interglacial ice melting phase, a network of connected rivers and lakes allowed primary freshwater fishes to disperse in the northern Palaearctic. Other fishes are relicts of earlier transgressions. Such species as herrings (Clupeidae), gobies (Gobiidae) and possibly sturgeons are believed to have evolved from the marine fauna of the Tethys Sea which ran from the modern Atlantic to the Indian Ocean before the Sarmatian basin formed. The uplift of eastern Anatolia and the Alborz in the Early Miocene between 20 and 17 million years ago (MYBP) closed a seaway from the Indo-Pacific which had extended into the Eastern Paratethys (= Black-Caspian-Aral sea in modern terms). The connection reopened in the Middle Miocene 16.8-16 MYBP) but by the Late Miocene a Sarmatian basin was cut off from the open seas and developed a unique marine fauna (Ekman, 1953). This was mostly lost as salinity decreased from freshwater input and a new fauna developed. A series of connections and breaks with the Black Sea, Mediterranean Sea and the Atlantic Ocean in various combinations with brackish and freshwater episodes gave varying opportunities for faunal interchanges and evolution. The Caspian fauna differs from the Mediterranean one because its only communication was via the Black Sea which acted as a "filter". When the Black and Caspian seas were well connected, the link to the Mediterranean was broken, and when the Black and Mediterranean seas were connected, the Caspian connection was not well developed. Mamedov (1997) and Rychagov (1997) review late Pleistocene and Holocene changes in Caspian Sea level, Chepalyga (1984) and Gerasimov (1978b) review water level changes and connections with the Black Sea over the last 80,000 years, Kosarev and Yablonskaya (1994) and Mandych (1995) for the last 500,000 years and Grigorovich et al. (2003) for the last 12.5 million years. Bianco (1990) gives an overview of the palaeohistory of the Paratethys Basin. Fluctuations in water level are correlated with climate changes Kotlík et al. (2008) using multiple gene phylogeography found the Black and Caspian seas supported separate populations of Rutilus frisii during the last glaciation, although this separation was not complete and gene exchange occurred, with the majority of migrations in the Pleistocene.

The total Caspian Sea drainage area is said to be 3,700,000 sq km, about 25% of the continental land mass of the U.S.A. (Rozengurt and Hedgpeth, 1989). The basin includes about one fifth of the crops and one third of total industrial output of the former U.S.S.R. (Rozengurt and Hedgpeth, 1989). Its northernmost waters are north of St. Petersburg (= Leningrad) in Russia while its southernmost waters rise on the flanks of the Zagros Mountains in Iran. This ranges from the subarctic to the subtropical region and is very diverse in climate and geology. Natural runoff in the South Caspian Basin ranges from 8 to 18 cu km while in the North Caspian it is 207-375 cu km. However the North Caspian is very shallow (mean 4-5 m, maximum 20-25 m) compared to the south Caspian (mean 325-334 m, maximum 980-1025 m). This is also reflected in the volume, 400-700 cu km compared to 49,000-77,500 cu km. Salinity is about 12-13‰, increasing in isolated bays and decreasing near river mouths. Summer temperatures in the south reach 27°C and in winter 9°C but the northern parts ice over. The Gorgan River area reached 30.9°C (Laloei, 2006). Surface water temperatures for the South Caspian are reported as 7.0-10.3°C in winter, 7.9-14.0°C in spring, 25.0-29.0°C in summer and 12.0-19.0°C in autumn (Rozengurt and Hedgpeth, 1989). These authors also report salinity ranges of 12.5-13.0, 12.3-13.2, 12.6-13.6 and 12.3-13.5‰ for the same seasons, oxygen levels of 7.0-7.8, 7.0-8.2, 5.0-6.0 and 6.0-8.0 ml/l, and pH values of 8.48, 8.44, 8.44 and 8.50. Vertical mixing occurs down to 50-150 m in the South Caspian (Mellat-Parast, 1992). There is little oxygen below 200-300 m and no fish life although changes to the hydrological regime of the Volga have increased aeration and oxygen content of deeper layers in the south Caspian, down to 600-800 m. The Caspian has no tides but sustained winds can cause seiches, local and temporary rises in sea level. There is a current along the Iranian shore from west to east. The shelf along the Iranian coast is narrow (6-10 km) and steep (Kosarev and Yablonskaya, 1994). Beaches are usually sand with shell gravel on the bottom further out. The extreme western coast has some shingle beaches and west of Alamdeh in the central part is some rocky shore but there are no major cliffs or headlands. The shore has coastal dunes, spits and bars with lagoons inland, either brackish or fresh, grading into the higher and dryer foothills.

Much of the coast was once forested, but it has been actively cleared and marshes reclaimed as rice paddy. Rice paddies are now being investigated for fish cultivation. About 300-500 kg of carp "seed" and a 10% increase in paddy production per hectare was recorded during the rice cultivation season. Extending this into the fall gave a production of 750-1000 kg of fish and duck and in winter 5.5-8.0 t of rainbow trout (Tehran Times, 1 October 2000). Gilan is attempting a production of 2 kg of trout per sq m of paddy field, with the aim of harvesting 46,000 t of fish (IRNA, 14 November 2001). Mazandaran has the highest farm fish production in Iran at 28,000 tonnes (2006-2007) and is expected to reach 50,000 t by 2010 (www.mehrnews.ir, downloaded 8 February 2007). The area of forests in northern Iran has been reduced from 3.4 million hectares in 1962 to 1.8 million hectares in 1977 and about 1 million hectares or less in 1995. In Gilan, 975,000 cu m of wood from the forests are burnt annually by cattle breeders for heating or cooking purposes or for production of dairy products. Additionally 450,000 cu m of wood are used for industrial purposes. Reforestation cannot keep up with the losses and forests have been reduced by half over the past 50 years (Barzegar, The Agricultural and Cattle Breeding Publication, No. 761, 22 December 1997, from www.netiran.com/Htdocs/Clippings/Deconomy/971222XXDE01.html). As a result floods now occur with destruction of fish habitat after 30-40 hours of rain where previously no flooding occurred after even 4 days of rain (Hamshahri, Tehran, 628, 20 February 1995). Abstraction of water for irrigation (60% of water use) has severely reduced water levels and runoff rates necessary for reproduction of fishes. Estuarine habitats have been degraded inhibiting the survival of eggs, larvae and juveniles of anadromous and semi-anadromous fishes (the latter are species which spawn in the lower stretches and deltas of rivers where salinity is optimal at 8 g/l for many commercial species, e.g. Sander lucioperca, Cyprinus carpio, Rutilus rutilus). Over 90% of coastal streams along the Caspian shore are dry in July in Iran because of irrigation demands. As a result larvae of spring spawners are flushed into fields where they die, migration and late summer spawning of Aspius aspius and Barbus brachycephalus are obstructed, and Salmo trutta caspius and Rutilus frisii kutum populations are depleted because they cannot spawn in the shallow, warm, weed-choked water. Nursery and reproductive areas for Abramis brama, A. sapa, Blicca bjoerkna, Aspius aspius, and Sander lucioperca among others are confined because of their low tolerance to salinities above 7-8‰. Without an adequate runoff, the sea encroaches on the estuary. Nasri-Chaari (1994) cites physical obstacles, sand removal from river banks, overfishing and water pollution for declines in fish migration in recent years.

An earlier, general work including fishes of the Iranian Caspian Sea and coast is Berg (1948-1049). A more recent work is the atlas of the fish species in the Iranian Caspian Sea in English and Farsi by Jolodar and Abdoli (2004).

The commercially important species of fish were summarised in Abzeeyan, Tehran, 5(7):VII-IX (1995) and are divided into sturgeons (Acipenseridae, 4 species) and bony fishes (3 species of kilkas in the genus Clupeonella of the family Clupeidae; herrings or Alosa spp. also in Clupeidae; 5 species of the family Cyprinidae namely Rutilus frisii, Cyprinus carpio, Abramis brama, Rutilus rutilus and Aspius aspius; 2 species of mullets, family Mugilidae, Liza auratus and L. saliens; a member of the perch family, Percidae, namely Sander lucioperca; and a member of the salmon family, Salmonidae, namely Salmo trutta caspius). About 70% of Rutilus frisii is caught in Gilan Province, while 60% of mullets and 75% of sturgeons are caught in Mazandaran Province. More than 50% of the sturgeon catch is Acipenser stellatus and 10% is Huso huso, the remainder being A. gueldenstaedtii and A. persicus, with a yearly catch for all sturgeons of about 2500 tonnes. Sturgeon fishing is carried out by the government and no private sector fishing is allowed because of the value of this fishery and the need for careful management. Accidentally caught sturgeon must be released or turned over to the government operation. Ivanov (2000) summarises the biological resources of the Caspian Sea from a Russian perspective with some comparative figures from Iran. Generally, catches in Iranian waters are always less than those in former Soviet Union countries combined. A particular exception is Rutilus frisii (safid mahi), an esteemed fish in Iran.

About 25% of the Iranian total fish catch is from the Caspian coastal area (CEP) and figures for the Iranian Caspian Sea in tonnes are:-

Year	All fish species	Kilka	Sturgeon flesh	Caviar
1976/77	8,428	1131	2368	221
1981/82	10,466	1341	1914	234
1986/87	11,084	2384	2500	303
1991/92	34,596	13,817	2208	283
1992/93	40,598	21,527	2198	262
1993/94	52,768	28,730	1170	217
1994/95	69,700	51,000	1700	218
1995/96	58,300	41,000	1500	182
1996/97	74,100	57,000	1600	195
1997/98	76,200	60,400	1300	151
1998/99	101,500	85,000	1200	157

The fish harvest from the southern Caspian coast of Iran for the 7 month period October 1999-April 2000 dropped by 11% over the same period from the year before, from 8630 t to 7710 t (IRNA, 10 May 2000). The decline was attributed to a rise in fish prices which encouraged illegal fishing and to habitat loss. The value for the whole Caspian fisheries is given as $6 billion by Nezami et al. (2000). A proposal for a Caspian Fisheries Commission is given by TACIS (1999; 2000b) and ERM-Lahmeyer International GmbH et al. (2001b). It would aim to conserve and utilise the living aquatic resources, including the management of fish stocks such as kilka, herrings and mullets, as well as the famous sturgeons. These species all have transboundary stocks requiring cooperative management between countries. Articles aim to protect traditional fishing for sturgeon along the Iranian coast, establish state monopolies for the export of caviar, set up cooperative research programmes to conserve sturgeon species, establish annual total allowable catches and fishing regulations, and so on.

About 50,000 tonnes of kilkas are caught each year by the Industrial Fishing Company and fishing cooperatives using deep conical nets and air lifting with artificial lights as attractants. About 20,000 t of other species are caught by licensed cooperatives using beach seines and gill nets although a report in IRNA (27 March 2000) cites more than 16,000 t including whitefish (Rutilus), Mugilidae, Cyprinidae, "anchovy" (sic), bream (Abramis) and zander (Sander). An account of site selection for beach seining is given by Zanoosi (1993). Beach seining has been restricted to the period from sunrise to 8 p.m., and to 10 p.m. in Miankaleh (www.iranfisheries.net, downloaded 14 November 2006). The 1994-1995 finfish catch (excluding sturgeon and kilka) using gill nets, coastal purse seines and beach seines, was 17,000 t, perhaps over 22,000 t with the illegal catch included. About 87% of this catch is Rutilus frisii kutum, Liza auratus and Liza saliens (Annual Report, 1994-1995, Iranian Fisheries Research and Training Organization, Tehran, p. 37, 1996). Gill nets showed a 39% decline compared to the previous year and beach seines were 16% less. Rutilus frisii kutum comprised 53%, mullet 39% and others 8% of the total catch (Abzeeyan, Tehran, 6(5, 6):IV, 1995). The harvest from the southern Caspian Sea coast dropped 11% in the year 2000 from the same seven month period in the preceding year, to 7710 t, as a consequence of poaching, neglect of river maintenance, and substandard capture methods (IRNA, 10 May 2000). The catch in Golestan Province rose from 470 t in 2000 to 3278 t in 2005, attributed to artificial propagation, restrictions on beach seining, training about closed seasons and beach seine standards, increased fishing effort, and a favourable climate (www.iranfisheries.net, downloaded 14 November 2006).

There are 5 regional fishing centres namely Bandar Anzali with 14 fishing stations, Keyashahr with 12 stations, Babolsar with 13, Ashuradeh with 9 and Nowshahr with 9 (Iranian Fisheries Research and Training Organization Newsletter, 7:7, 1995). The Caspian Environment Programme (2001c) gives 15 stations for Bandar Anzali, 9 for Keyashahr, Babolsar, Ashuradeh and Nowshahr for sturgeon fisheries. Fixed gill nets are used with a standardised mesh. The Ashuradeh Peninsula, where more than half of Iran's caviar is processed, was threatened by the rising Caspian Sea in a 1991 radio report. A 1995 agreement between Iran, Azerbaijan, Turkmenistan, Kazakhstan and Russia gives each nation an exclusive fishing zone of 20 nautical miles from shore (Iranian Fisheries Research and Training Organization Newsletter, 7:7, 1995).

Inland freshwaters of Gilan are divided into three categories by Bakhshizod-Mahmoodi (1996): natural and impounded ponds, the Safid River reservoir, and wetlands. The ponds are used primarily for cyprinid and acipenserid culture, the reservoir is fished by seining, by spreading wheat grains in littoral areas to attract fish and by using the shemshad or shaghoul net (a giant dip-net), and the wetlands are fished by seining, by the salik or mashak (cast-nets), by the la'kesh (drifting gill net using one and two boats), by fixed gill nets, by the shemshad and by angling (for ordak mahi).

Pollution is an important factor in the ecology of the sea, from offshore oil drilling, ship discharges of oil wastes and contaminated water as well as garbage and even discharges from ship collisions, radiation from underground, non-military explosions and nuclear waste dumped in inflowing rivers (radiation levels are 100 times above normal (Time, 1 November 1993)), manure and pesticides from farming on the surrounding land mass, city waste water, sewage and garbage, industrial wastes including mercury and other heavy metals, discharges from water desalinating plants, extraction of minerals such as sodium sulphate, mirabelite and espomite, and untreated sewage (see Sardar (1979), Nuhi and Khorasani (1981), Coad (1980c), Khalili (1994), Raiss-Tousi (1999), Namazi (2000), Abaee (2001), Charamlambous (2001) and Laloei (2006) for Iranian problems; Anonymous (1988c), Edwards (1994), Specter (1994) and Kasymov and Rogers (1996) for former Soviet waters; Stone (2000b) is a recent, short general overview).

Data collected in 1991 showed the Caspian Sea received effluents comprised of 3000 tonnes of oil products, 28,000 t of sulphites, 315,000 t of chlorides, 200,000 t of tar and 25,000 t of phenols (Namazi, 2000). In Daghestani rivers, the same author records heavy metals, pesticides, phenol, arsenic, boron and selenium, among others, at 60-100 times the maximum permissible for fisheries. The oil industry is considered to be the main source of ecological problems in the Caspian Sea (Karpyuk, M. and Shavandin, V. 1996. Astrakhaners on the Caspian Sea. International Affairs, 42(1) from http://home.eastview.com/ia/42_01_15.htm). Prospecting uses blasting operations which have caused sturgeon deaths on more than one occasion. A single offshore well during its life releases into the water 30-120 tonnes of oil, 200-1000 t of sand, clay and other waste and 150-400 t of drilling mud paraffin fractions, baryta, lime, detergents, emulsifiers and lubricants. The ecology is affected 5-12 km from each well. The oil industry in the Caspian has reserves estimated at $4 trillion and a new oil rush will further contaminate the sea.

Charamlambous (2001) concludes that municipal wastewater from 11 million people is the primary pollutant in Iranian coastal waters. Industrial discharge accounts for 31%. of organic loading, the rest being municipal discharge. The most industrialised area is around Rasht with waste going into the Anzali Mordab. TACIS (2000c) reports that in Gilan, 32 of 36 major cities discharge wastewater untreated into a river and 89 of 90 industries discharge treated wastewater to a river. Ayati (2003) also reviews pollution in the mordab. Mirkou (2001) details agro-chemical usage along the Caspian shore comprising various fertilisers and pesticides.

Chlorinated pesticides have been used in anti-malarial campaigns throughout Iran and to eliminate pests on cotton, rice and other products in Mazandaran. Herbicides and pesticides are widely used in rice paddies. DDE, DDT, DDD, Lindane, Dieldrin, Eindrin and Kelthane have been identified in such rivers as the Babol and Chalus (Annual Report, 1995-1996, Iranian Fisheries Research and Training Organization, Tehran, p. 11-13, 1997). Ebadi and Shokrzadeh (2006) examined Rutilus frisii, Vimba vimba, Clupeonella delicatula and Liza aurata for lindane at Chalus, Babolsar, Khazarabad and Miankaleh but levels detected were less than the FAO/WHO recommended permissible intake and were no cause for public concern. Similar studies on DDT and DDE and on chlorobenzilate from the same sites and fish and levels were also less than the permissible intake (Shokrzadeh and Ebadi, 2005; 2006). The Chalus River also contains various heavy metals, such as lead, zinc, copper, iron, cadmium and chromium from mining activities (Annual Report, 1995-1996, Iranian Fisheries Research and Training Organization, Tehran, p. 18, 1997). Hashemy-Tonkabony and Asadi Langaroodi (1976) have shown the presence of DDE, DDT, TDE, Dieldrin, Lindane, Aldrin and Heptachlor in a wide variety of Caspian fishes in Iran. However, Ebadi and Shokrzadeh (2006) examined Rutilus frisii, Alburnus, Clupeonella and Liza species in Mazandaran for the organochlorine pesticide lindane and found levels in muscle tissues to be less than FAO and WHO recommended permissible intake and so were not a public concern. Rutilus frisii, Cyprinus carpio, Liza species and Acipenser stellatus were tested for DDT, aldrin and heptachlor with only the latter slightly elevated above standard levels at Hashtpar (Iran Daily, 11 January 2006). Phytoplankton diversity in the western Caspian Sea fell from 74 to 40 species, biomass from 8.7 to 2.1 g/ sq m and biomass of benthic organisms in coastal areas fell from 1724 g/ sq m in 1961 to 21 g/sq m in 1969 (Clark, 1986). These declines were noted particularly in the nursery grounds for sturgeon, Abramis brama, Esox lucius and Cyprinus carpio among other fish species. In the 1980s, catches of Abramis brama, Cyprinus carpio, Rutilus rutilus and Sander lucioperca fell by as much as 80% and Salmo trutta caspius and "shad" had almost disappeared. It was estimated that for 1985, 10,200 tonnes of oil products and 104,200 t of sewage were dumped in the sea. One-fourth (or 40 billion cubic metres) of all the wastewater in Russia enters the Caspian Sea and petrochemical factories alone release 67,000 t of waste annually (Anonymous, 1988c; Platt, 1995; Hamshahri, Tehran, 3 (639), 7 March 1995). Salinity increased as more water was taken for irrigation - two-thirds of the Terek and Kura flows did not reach the sea (Markham, 1989). In Iran, sewage is discharged into the Caspian Sea from coastal towns, and via rivers, from towns inland. Industrial solid wastes enter the sea through the larger rivers such as the Safid, Gohar and Siah as well as the Anzali Mordab complex. The use of agricultural chemicals such as fertilisers and pesticides has led to pollution, e.g. in Gilan Province 88,851 t of fertilisers were used in the year 1992-1993, an 18.7% increase over the previous year. A survey of 30 towns in Gilan shows that 80% of rubbish dumps are located by rivers, marshes or the coast (Hamshahri, Tehran, 3 (639), 7 March 1995). An estimated 200,000 fish were killed in the Kacha River, a branch of the Siyarud in Rasht, poisoned from a dump in the Saravan region which receives 390 t of rubbish daily. Heavy rains had washed poison into the river (Tehran Times, 7 October 1998). As many as 1000 trout (presumably mahi azad, Salmo trutta) died in the Kileh River in Mazandaran from release of wastes from a dairy manufacturer; sand extraction was also blamed for affecting fish populations (Iran Daily, 21 July 2005).

The biology of the Volga River and its effects on the Caspian ecology has been reviewed by Rozengurt and Hedgpeth (1989) and Pavlov and Vilenkin (1989). This river is of critical importance for marine fisheries. Fish production is less in the central and southern parts of the sea as nutrient supply comes from upwelling and circulation rather than a riverine input. However the Volga has effects even here, changing the Caspian Sea from its regime in the 1950s. Abstraction of water for irrigation, industry and household use caused salinity increases of about 0.2-0.3‰, increased aeration of deep layers and in their oxygen content down to 600-800 m by as much as 2-3 ml/l due to convection and thermal winter mixing, an increase in the euphotic zone to 50 m and depths open to total photosynthesis to 100 m, a decrease in organic matter and its vertical gradient, and an increase in wind-driven circulation and its effects on temperature and salinity layers. In the period 1956-1972, the Caspian Sea was transformed from a fishery based on valuable species (listed above) to one dependent on kilka which now occupies 80% of the catch (or 107 times the catch in 1930). Even including the kilka, catches in the 1970s were 245 x 10³ tonnes or only 37% of the 1913 catch. The catch of Caspian herrings (a complex of species in the family Clupeidae) ceased to exist commercially by the 1970s and in fact was banned. In 1967-1972 it was 0.6-2.1 x 10³ compared to 56-62 x 10³ in 1945-1953 or 82-307 x 10³ in 1900-1917 (Rozengurt and Hedgpeth, 1989). Moghim et al. (1994) report that, in the southern areas of the Caspian Sea, nearly 90% of the catch is composed of Rutilus frisii, Liza saliens and Liza aurata (with biomasses of 24,000, 7000 and 2400 t respectively and maximum sustainable yields of 7000, 2900 and 960 t  respectively). The Volga is a major pollutant of the Caspian Sea, carrying sewage, agricultural waste, PCBs, petrochemical wastes, tannery waste, etc. from a population base of 60 million people (Golub, 1992). In 1989, 40 million t of polluted wastewater entered the Caspian via the Volga River, more than a quarter of all the wastewater of Russia (http://www.oneworld.org/patp/pap_overview.html). A report in 1995 gives the volume of pollutants and industrial wastes entering the Caspian Sea each year as 11 billion cu m. Russia accounts for 50%, Azerbaijan 16% and Iran 11% (http://netiran.com/news/IRNA/html/950731IRGG17.html).

The Volga-Don canal in the former U.S.S.R. connected the Caspian Sea with the Black Sea in 1952 and formed an invasion route for various benthic organisms while others came in attached to boats transported by rail or were deliberately introduced (Kasymov, 1982). The molluscs Abra ovata and Mytilaster lineatus, two invaders, accounted for over 90% of the total benthic biomass. Invaders provided 95.1-99.3% of the total benthic biomass in the western part of the south Caspian Sea in 1976. East of the mouth of the Safid River, the Azov-Black Sea molluscs Abra ovata and Cerastoderma lamarcki accounted for 80% of total benthic biomass. In Gorgan Bay, 99.9% of the benthos fauna is comprised of invaders. The Volga is also connected to the Baltic and White seas via the White Sea-Baltic Canal opened in 1933 (Pavlov and Vilenkin, 1989).

The fisheries may well collapse if the 10 cm long ctenophore or comb jelly Mnemiopsis leidyi from the northwestern Atlantic Ocean enters the Caspian Sea via the Volga-Don canal in ballast water. It reached the Black Sea in the early 1980s and destroyed the local pelagic food chain (Travis, 1993; Dumont, 1995; Pearce, 1995; GESAMP, Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection, 1997; Negarestan et al., 2002; Kideys, 2002a; 2002b; 2003). The ctenophore eats fish eggs and larvae directly as well as zooplankton and crustaceans which are foods for fish (Bagheri et al., 2005). The Black Sea fish catches fell 90% in 6 years and the biomass of the ctenophore reached an estimated 900 million tonnes, ten times the world annual fish catch (or 1 billion t, about equal to the world fish catch - sources differ). The wet weight biomass of the whole Black Sea at times was 95% ctenophore. This suggestion of the mid-1990s was borne out, as detailed below. A continuing series of reports, magazine articles and studies on this invader are not all cited here.

The earliest report for the Caspian appears to be in 1995 by the Iranian Fisheries Research Organization (Bilio and Niermann, 2004; www.caspianenvironment.org/mnemiopsis/mnem_attach13.htm). The Islamic Republic News Agency (IRNA) on 12 May 1998 reported that a number of jellyfish had been observed in the Caspian Sea recently, presumably brought in the ballast of oil tankers, and its occurrence is documented by Esmaili Sari et al. (1999) and in numerous other studies by this author and co-authors. Various studies on the biology of the comb jelly have been carried in the Iranian Caspian Sea including, e.g. Movahedinia et al. (2002) and Yussefian (2002).

The kilka fisheries are now threatened by the comb jelly which spread through the entire sea by the year 2000. J. Muir (http://news.bbc.co.uk/hi/english/world/middle_east/newsid_1453000/1453117.stm, downloaded 30 August 2001), Kideys (2002b) and Kideys and Moghim (2003) report a 50% drop in kilka numbers with catches down from 3-6 t per night to half a tonne for one boat. A 50% decrease in kilka catches meant a minimum U.S.$15 million loss to the fishermen (Kideys and Moghim, 2003). Iran's kilka fishery fell from 85,000 t in 1999 to 15,000 t in 2004 and losses exceed $125 million (Stone, 2005a). This comb jelly can double in size in one day, reaches maturity in 2 weeks and then produces 8,000 young every day. Maximum abundance reached 5122 individuals per square metre in October 2001 and biomass 1024.5 g/sq metre in august-October 2002 (Roohi et al., 2003; Bagheri, 2004; 2006). The fisheries may recover somewhat after the comb jelly population collapses (Tidwell, 2001b). The website www.caspianenvironment.org/mnemiopsis/index. htm, downloaded 9 April 2003 and Dumont (2002) have extensive information on this problem and Stone (2002b) and IFRO Newsletter (29:4, 2001) confirm a severe depression in kilka and herring stocks. Beroe ovata, a comb jelly that preys on Mnemiopsis, is being cultured in Iran (Kideys, 2002b; Kideys et al., 2004; Rezvani Gilkolaei et al., 2005; Mirzajani, 2006; Mirzajani et al., 2007) and does not appear to feed on other organisms in the Iranian Caspian (Iranian Fisheries Research Organization Newsletter, 38:3, 2004). Reproduction and growth are slower, and mortality higher, than in the Black Sea, due either to the lower salinity in the Caspian Sea water or damage to individuals during transportation for the experiments. If this comb jelly fails to control Mnemiopsis, the introduction of the exotic American species, the butterfish (Peprilus triacanthus), known to feed on ctenophores has been advocated but this fish could also feed on other fishes (Harbison, 2002; Bilio and Niermann, 2004). The complex politics of the nations surrounding the Caspian have prevented the introduction of Beroe (Stone, 2005a).

The Kara Bogaz Gol ("Black Throat Bay"), an eastern arm of the Caspian Sea in Turkmenistan, is 160 km long by 140 km broad (18,389 sq km) but only 2-3 m deep. It acts as a salt precipitator. This water body was blocked off by a dam to conserve the water lost in it by evaporation in 1980. The Caspian Sea has a net annual water deficit of 15 cu km with 5 cu km being lost through the Kara Bogaz Gol alone (Rich, 1982; 1983). However this resulted in salts being spread by the winds, ruining fish spawning grounds and fish farms in the Caspian basin, and ultimately would lead to the salinisation of the Caspian Sea. A dike has now been constructed to allow some flow into the Kara Bogaz Gol and allow the flushing effect to operate. The refilling process over 3 years prevented a 35 cm rise in the Caspian Sea level (Dumont, 1995). Use of this water body to reduce level rises in the Caspian Sea and prevent flooding has been proposed (Wardlaw, 2001). Fish which enter the salty Kara Bogaz Gol lose their swimming capacity, become blind and thrashing about often come to lie on the shore. Birds eat them but those that are missed become salted and dried and may be preserved for a year or so. The Turkmenistan government re-established natural flow into the Kara Bogaz Gol in 1992 because of the Caspian Sea level rise (Zonn in Glantz and Zonn (1997)).

The Caspian coastal plain in Iran runs for almost 650 km from Astara (38°26'N, 48°52'E) in the west to Bandar-e Torkeman (= Bandar-e Shah) (36°56'N, 54°06'E) in the east. This plain has a width of about 25-32 km, but is as narrow as 2 km in places, although it opens out in the east. The Alborz Mountains are almost 1000 km long, on average less than 100 km wide but very high. Damavand reaches 5766 m - an estimate - at 35°56'N, 52° 08'E and is the highest of any mountain to the west of it in Europe and Asia. It has a continuous snow cover. There are persistent snow fields and Alam Kuh at 4849 m has small icefields. The north or Caspian slope is very steep and streams tend to be short and torrential, fed by snow melt and year-round rain. However there are some longer rivers and the principal ones are detailed below. There are about 128 small to large rivers along the Caspian shore. Nümann (1966) gives some limited biological, chemical and physical data on these streams based on spot recordings. Surber (1969) gives values of total alkalinity and calcium-magnesium hardness for a number of streams and reservoirs along the Caspian shore. Most were moderately to relatively hard and therefore productive for aquatic organisms such as insect larvae on which fish feed. The Caspian Environmental Programme (2001b) gives an overview of habitats and biodiversity along this Iranian shore. Environmentally managed areas are listed along with factors affecting their status under the headings of development, drainage, land use alteration, pollution, destruction of vegetation, over-grazing, mining, hunting and fishing, exotics, dams, and roads. Of 123 fish species only 10 or just over 8% are protected with one protected species on the verge of extinction.

Most rivers along the Caspian shore have less than 30% of their discharge in the two wettest months and 40% in the six driest months so discharge is well distributed through the year. In contrast, the Gorgan River at the eastern end of the Caspian basin has 70% of its discharge in the two wettest months, figures comparable with drier areas such as Azarbayjan at 50-60% and the Zayandeh and Kor rivers at 40-60%. Annual discharges can vary markedly, e.g. the Lar River had 545 mm on its basin area in 1949-1950 and 1560 mm in 1950-1951 (Ghahraman, 1958).

The Aras (= Araxes or Araks) is a tributary of the Kura River of Azerbaijan. The Kura rises in Turkey and is 1510 km long. The Aras forms the border between Iran and the former U.S.S.R. (now Azerbaijan and Armenia) for 430 km and has its source near Erzurum (39°55'N, 41°17'E) in Anatolia and the headwaters of the Euphrates River. Its total length is 1072 km. The Aras can be wide and meandering with braided channels and backwaters. Depth range of the Aras is 0.5-4.0 m, average 2.5 m (Zakeri, 1997). The Araxes or Aras Dam was a joint Iranian-Soviet project on this river. Iranian authorities stocked the dam with 1.8 million fingerlings (species not specified) weighing over 10 g each in 1997 to enhance fish farming (Islamic Republic News Agency, 29 December 1997). Akh Gol occupies 600 ha at 820 m in the Aras River valley in northeastern Iran (Scott, 1995). It comprises a small brackish lake with associated marshes and springs and rains to the Aras 5 km away. The area is being converted to agriculture and the lake is being drained. Principal tributaries of the Aras in Iran are the Qareh Su (= black water, draining easily eroded, volcanic soil) draining from the Kuhha-ye Sabalan at 4810 m (38°15'N, 47°49'E) near Ardabil (38°15'N, 48°18'E) and the Qotur River draining past Kuh-e Zaki at 3079 m on the Turkish border through Khvoy (38°33'N, 44°58'E) to the Azerbaijan border near Jolfa (38°57'N, 45°38'E). The Aras and the Safid are two of the three largest rivers in Iran (with the Karun River of Khuzestan). The Kura-Araks basin encompasses 225,000 sq km of which 28,000 sq km or 12.4% is found in Iran (Gleick, 1993). Azerbaijan discharges 303 million cu m of waste into the Caspian Sea annually according to Golub (1992), presumably through the Kura and other major rivers.

Derzhavin (1929a) gave an interesting account of the formation of a new channel of the Aras north of the Iranian border in 1896 which led to the freshening of the Kyzylagach Bay. This favoured migrations of fishes into the Kura River. However, irrigation schemes on the Mugan steppe severely reduced catches as well as causing salinisation of soil. Water abstraction prevented entry of adequate numbers of sturgeons onto the Kura spawning grounds. This type of water usage is paralleled along the Caspian shore in Iran with deleterious effects on a variety of sedentary and migratory fish species.

The Safid (= Sefid or White from its sediment load, up to 60 g/l) River is the only one to completely pierce the Alborz Mountains and has a considerable basin (54,100 sq km) on the plateau. Various sources give differing accounts of its length, up to 800 km. The Safid has the greatest mean discharge of Iranian Caspian rivers, over three times that of the Heraz, the next most important. In flood the Safid discharge is twice that of the Karun, but its minimum is less than a tenth, because the Karun drains a greater area with higher elevations and a more extensive snow pack. The Safid discharge is 4000 cu m per second at maximum, falling to only 15 cu m per second. An average discharge is 182.17 cu m per second. There used to be two freshets before the dam was constructed at Manjil, one fed by spring snow melt in March-May and one by rainfall in the autumn. The rise in water levels and increased sediment load attracted sturgeons, in particular Acipenser persicus. The catch of this species and A. gueldenstaedtii in the Safid River area reached 733,127 kg in 1927/1928 representing 46,500 fish and a caviar yield of 120,958 kg (Vladykov, 1964).

The width of the Safid River varies from 100 to 250 m and depth from 2 to 8 m. The average instant yield is 128.79 m/sec, range 76.5-288.5 m/sec. The average annual yield is 3,998.4 million cu m (Zakeri, 1997).

The Safid is formed from the Qezel Owzan from the west and the Shah River from the east which meet on the plateau and flow through a narrow gorge. This gorge is dammed by what was named the Shahbanou Farah Dam at Manjil (now the Safid or Manjil Dam) (dam height 106 m, length 425 m; reservoir 1860 million cu m, surface area 56 sq km maximum, 14 sq km minimum, maximum depth 80 m, minimum 30 m, summer temperature 24°C, winter 7°C, pH 7.8, 31 g/l turbid materials, Cl^- 229 mg/l, SO₄ 178 mg/l). Strong water level fluctuations prevent the development of a belt of vegetation and the heavy sedimentation inhibit a bottom fauna. Khodjeini and Mohamed (1975) detailed the rate of sediment accumulation in this dam, 757 cu m/sq km/year, evidence of severe erosion of a devegetated drainage basin. The reservoir was half filled with sediment after only 20 years despite an expected life span of 100 years. The reservoir is apparently drained at intervals to remove some of the accumulated sediment. This would severely affect littoral spawning and feeding habitats for fishes. Nümann (1966, 1969) gives details on the limnology of this reservoir. The dam decreased turbidity in the river, raised water temperatures at the river bed in summer and caused marked diurnal temperature changes. This prevented ascent of Salmo trutta to the upper reaches and the dam itself prevented ascent of Rutilus rutilus. Nümann (1966) recommended introducing Sander lucioperca, Acanthobrama terraesanctae (a Levantine species) and cichlids to the reservoir.

Lower dams on the Safid, such as the Tarik (10 m high) and the Sangar (3 m high), divert water for irrigation purposes on the Gilan plain, the former through a 16.7 km long tunnel.

The Safid breaks up into distributaries near its mouth and its flow is carried off into a complex of canals and irrigation ditches. The Safid has changed its delta several times, (Vladykov, 1964). In 1911 it shifted 2-3 km east from the fishing post of 12 Bahman to Hasan Kiadeh. An account in Farsi on the Safid River is given by Wossugh-Zamani (1991b).

The headwaters of the Qezel Owzan lie in Kordestan, near the Iraqi border, and so drain part of the northern Zagros Mountains as well as areas near Lake Orumiyeh such as the Kuh-e Sahand (37°44'N, 46°27'E), mountains near Hamadan (34°48'N, 48°30'E) and the southern slopes of the Alborz Mountains. The Qezel Owzan is about 550 km long. The Taham Dam project 12 km northwest of Zanjan lies in the Qezel Owzan basin on the Taham Chay. This dam is to be 120 m high with a crest length of 450 m and a capacity of 82.7 million cu m. The fish fauna behind the earth dam at "Maljiq", 50 km southwest of Hashtrud in the upper Qezel Owzan basin, suffered severely in the drought of the year 2000. Twenty-five tonnes of fish died after the reservoir dried up (www.irna.com/newshtm/eng/09151847.htm, IRNA, 30 July 2000).

The Shah River is much shorter (ca. 175 km) than the Qezel Owzan and drains the southern Alborz as far east as Takht-e Soleyman at 4819 m (36°22'N, 50°58'E).

The 500 ha Bandar Kiashahr Lagoon (= Bandar-e Farahnaz) Ramsar Site (World Conservation Monitoring Centre, 1990) at 37°25'N, 49°19'E east of the mouth of the Safid Rud was a freshwater coastal lagoon and swamp fed by two streams from the Safid Rud to the west and draining to the Caspian Sea via a channel to the north. The recent rise in Caspian Sea level has converted this area into a bay of the sea as it was in the 1950s before the fall in sea level (Khan et al., 1992). The lagoon bed is sand and mud and the water was oligotrophic except near the marshes to the west. There were reedbeds of Phragmites communis, Typha and Juncus, now restricted to the extreme west end. There were several factors affecting this habitat including a fishery with a fish-processing warehouse, grazing, reed cutting, irrigation abstraction and recreational activities. It was an important spawning and nursery ground for fishes (effects of recent changes unknown) and is still an important centre for commercial fishing.

The Heraz River drains the Alborz east of Tehran and has a number of longitudinal tributaries in the mountains. These depend on snow melt and are cold even in summer. Fishes are reported to be present in these high streams, but were not easily caught. The Heraz debouches onto a plain and splits up into distributaries. It is polluted from rainbow trout farms (Kazemzadeh Khajuie et al., 2002) and heavy metals (lead and cadmium) are present in fish (Riahi Bakhtiyari, 2001; 2002). The Tajan or Tadjan River was studied by Ro(o)shan Tabari (1995; 1996) who reported on its hydrology and biology. Its mouth lies at 36°49'N, 53°05'E. The maximum flow is in April, decreasing from May onward. In April 1989 flow was 45 cu m/sec falling rapidly to 0.11 cu m/sec in June. Over 70% of the fishes are anadromous with sturgeons being the most important species (Acipenser persicus, A. gueldenstaedtii and Huso huso). Salmo trutta is the most important species in the upper reaches. Other species found in this river are Cyprinus carpio, Alburnus sp. (presumably Alburnus alburnus), Capoeta capoeta, Barbus capito, Vimba vimba, Alburnus chalcoides, Rutilus frisii, Rutilus rutilus, Liza sp., Gobiidae, and Esox lucius. Rural, agricultural and industrial pollutants are found in the Tajan and affect the fishes along with dams and other physical obstacles, sand removal and overfishing. The Shahid Rajaee Reservoir Dam, inaugurated in 1997, is found on this river 41 km south of Sari (http://netiran.com/news/IRNA/html/951016IRGG15.html and http://netiran.com/news/IRNA/current.html#HLNO4). The Independent (London) reported on 13 July 1994 that tens of thousands of fish died in this river after poachers poured poison into it about 9 miles (14.4 km) above the estuary. Dead fish covered the river bed for 6 miles (9.6 km).

The south-eastern corner of the Caspian Sea receives two major rivers, the Gorgan and the Atrak or Atrek (ancient Sarnois). Their courses are roughly east-west and parallel each other with the Atrak forming part of the border with Turkmenistan. The Atrak is 495 km long (with 145 km of this in Turkmenistan; Nezami et al. (2000) state 715 km for the Atrak) and the Gorgan 240 km. The Gorgan drains 10,200 sq km and has an average discharge of 9.39 cu m per second (cf. Safid River with 182.17 cu m per second; the Chalus River, directly north of Tehran, has a discharge of 12.65 cu m per second). The Voshmgir or Sangarsavar Dam at 37°12'N, 54°45'E on the Gorgan stores 60 million cu m of water. The water level fluctuates markedly, banks are steep and there is little emergent vegetation. The Golestan Dam (same as preceding?) is 20 km north of Gonbad-e Qabus on the Gorgan River and has a capacity of 86 million cu m. Keivany et al. (1990; http://gause.biology.ualberta.ca/Keivany/bsc/html - 1996) report an irregular pH range for the Gorgan River from 6.3 to 7.9 with an average of 7.1. Temperature range was 8 to 33°C. Conductivity varied greatly from 667 to 10,000 µM/cm, with an average of 875 µM/cm. Chlorides, especially sodium chloride, were the most abundant soluble salts. Total dissolved solids varied from 21 mg/l to 4300 mg/l in an inverse relationship with water volume. Water volume at the dam inlet varied from 2 to 75 m³/second and almost 52% of the sediments entered the dam during a high flood. Water quality was assessed as polluted. The major fish species were Cyprinus carpio, Barbus barbus (sic - possibly B. capito), Alburnus spp., Cobitis taenia, Gambusia affinis, and Carassius carassius (sic - presumably C. auratus). A fish kill noted by Coad (1980c) in 1978 was attributed by local informants to careless insecticide spraying on fields neighbouring the Gorgan. Newspaper and radio reports variously stated that 200 barrels of a highly toxic chemical spilled into the river when a truck overturned and that the chemical, identified as Turbidan from the Trintext chemical plant, was dumped by a technician commissioned to get rid of the waste product (Kayhan International, 7 May 1978).

The Atrak headwaters are close to those of the Tedzhen basin. The Atrak basin comprises about 40,000 sq km. The Atrak is only about 10-15 m wide and about 0.5 m deep over much of its lower course. It only reaches the Caspian Sea during floods. A tributary of the Atrak from Turkmenistan is the saline Sambar River, about 203 km long. Petr (1987) reports that efforts were being made to divert this river so as to increase the water quality in the Atrak. The fresh section of the Atrak has a conductivity of 2362 µS and the saline section 23,500 µS. The Caspian Sea off the Atrak River is an important fishery economic zone. Gasan-kuli or Hasan Kuli is a town in Turkmenistan near the Iranian border referred to in fishery reports from this area. The catch of Rutilus rutilus, Cyprinus carpio and Sander marinum was nearly 1.44 x 10⁴ tonnes with only 1.9% being accounted for by Clupeonella cultriventris. However by 1972 the catch of the commercially important species had declined to 1.5% and the less desirable Clupeonella had increased to 5.73 x 10⁴ t or 98.3% of the catch. The causes were reduction in the Atrak runoff through irrigation withdrawals, pollution from agriculture, overfishing in the sea and the drop in sea level. Flows of the Atrak did not reach the sea in 1984, 1986, 1990 and 1991and spawning of species using the lower reaches did not occur (Caspian Environmental Programme, 2000).

There are 5 lakes along the Atrak, fed by the river, which have been recently dyked to improve water retention. Their fauna is dominated by native cyprinids. The lowest lake is saline and they range in size from 400 to 2500 ha.

The lakes Alagol or Ala-Gol at 37°21-22'N, 54°35'E, Ulmogol, Alma-Gol or Ulmagol 37°24-25'N, 54°38-39'E and Ajigol or Adji-Gol at 37°24-25'N, 54°40'E comprise a Ramsar Site (World Conservation Monitoring Centre, 1990; Scott, 1995) near the frontier with Turkmenistan just east of the Caspian Sea. Alagol occupies 1400 ha (Scott (1995) states 900 ha) and both Ulmogol and Ajigol 200 ha (Scott (1995) states 280 ha and 360 ha respectively). The Alagol Lake is slightly saline with a mud and sand bottom. It is fed by springs, seepage and precipitation and may dry out completely in summer. It overflows westwards when full. Vegetation is sparse with Juncus, Carex and grasses mainly in the northeast and small patches of Phragmites communis. It is oligotrophic and vegetation poor. The other two lakes have seasonal fresh water fed by precipitation and have a mud and clay bottom. They are eutrophic and water levels vary greatly so that they may dry up completely. Ulmogol has little vegetation such as Juncus, the duckweed Lemna, Phragmites communis, Alhagi and algae while Ajigol has extensive Phragmites reedbeds at its eastern end and abundant submerged vegetation. Fishing occurs in the lakes and the habitats are affected by cattle grazing and reed cutting. Water is abstracted for irrigation and for a fish hatchery. In Alma-Gol and Ala-Gol, 90.91% and 82.18% of the total frequency of fishes was comprised of exotic species. Hemiculter leucisculus was the most frequent in Alma-Gol (58%) and Adji-Gol (16.82%) and Carassius auratus in Ala-Gol (77.6%). Other exotics were Gambusia holbrooki, Pseudorasbora parva and Cyprinus carpio (Patimar and Kiabi, 2005).

The Qareh Su (= Gharesoo) is another river entering the Gorgan Mordab. In its upper reaches it has a rocky bed and a fauna of Nemacheilus malapterurus, Capoeta capoeta and Alburnoides bipunctatus, resembling the grayling zone of Europe. The central part of the river dries up (the barbel zone) while the lower river (bream zone) is brackish from gulf input, has high temperatures and pollution. This lower zone has Carassius auratus, Alburnus alburnus, Cyprinus carpio, Pseudorasbora parva, Gambusia holbrooki and Gasterosteus aculeatus with Atherina boyeri, Neogobius kessleri, Neogobius melanostomus, Neogobius fluviatilis, Knipowitschia caucasica, and Liza saliens feeding in the estuary, and Acipenser stellatus, Alburnus chalcoides, Cyprinus carpio, Rutilius rutilus and Vimba vimba migrating into the river for reproduction.

Incheh Borun Lake at 37°13'N, 54°30'E is a small and isolated freshwater body of 50 ha about 40 km north of Gorgan. Lake Bibishervan at 37°09'N, 54°52'E and Lake Eymar at 37°08'N, 54°52'E are two more small isolated freshwater lakes occupying 300 ha and 250 ha respectively. All three lakes lie on a cultivated plain. The fish faunas of these lakes are unknown.

The Golestan National Park lies between Bojnurd and Gonbad-e Qabus and is divided by the Tehran-Mashhad highway. The Iran Nature and Wildlife Magazine (volume 3, 1999; downloaded from its English website) states that fish in the Doogh River include rainbow trout and Umbra krameri (sic), both exotics. The latter species is an error of translation from Farsi to English of common names (B. Kiabi, pers. comm., 23 February 2000). A description of the park is given by Kiabi et al. (1994).

The Anzali (= Enzeli or Pahlavi) Mordab (37°26'N, 49°25'E) is a freshwater to brackish lagoon (Firouz, 1968b) separated from the Caspian Sea by a sandy barrier about 1 km wide. The more modern term is "talab" (= pool or marsh, which lacks the association with death) but the older literature refers to mordab and the term is still in common use. It is surrounded by ab-bandans such as the Selke Ab-bandan of 360 ha at 37°24'N, 49°29'E which is protected as a Wildlife Refuge. Ab-bandans are a feature of the Caspian coastal plain, being a shallow and artificial freshwater impoundment managed in winter for duck hunting and in summer as an irrigation reservoir. The Anzali Mordab complex of 15,000 ha is a Ramsar Site and this includes the whole mordab, the Siah-Kesheem marshes, Selke Ab-bandan and several other ab-bandans. The main mordab comprising open water is 26 km long and 2.0-3.5 km wide encompassing about 11,000 ha. Reed beds extend the eastern limit by a further 7 km. The Siah-Kesheem (or Siah-Keshim) Protected Region has a lagoonal surface area of 4500 ha (Khara, 1994; 6700 ha in Scott, 1995) and is about 12 km long by 4.5 km wide. It lies to the southwest of the main mordab, of which is was probably once part, and is fed by the Esfand River. Note that Khan et al. (1992) state that the Anzali Mordab is unprotected except for the Siah-Kesheem Protected Region and the Selke Ab-bandan of 360 ha. A description of the Siah-Keshim Protected Area is given by Riazi (1996) and of the wetland generally by Monawari (1990). Important fishes are listed as Sander lucioperca, Cyprinus carpio, Silurus glanis and Esox lucius (Iran Nature and Wildlife Magazine, 5, www.neda.net/inwm/no.5/english/pre_sites/pre_sites01.html, downloaded 8 March 2000).

The main mordab is drained by the Sowsar Roga, Pir Bazar Roga, "Raste-Khaleh" (? Rasteh Kenar) Roga, Nahang Roga and Pahlavi or "Koulivar" (? Kolver) Roga over a distance of about 4 km to the Caspian Sea. Warm, dense and saline sea water is able to penetrate up these effluent rivers for as much as 10 km, which generally have low flow because of water abstraction and seasonally low precipitation, because of the rise in sea level since 1977. Fresh water flows across the surface of the saline water mixing at depths of 0.5-2.0 m. Salt water contamination is always a danger as more water is abstracted in this heavily populated and farmed area (Kimball, 1973; Kimball and Shayegan, 1973; Sharifi, 2006). Abdolmaleki (1994) gives some data on the benthic macrofauna of this lagoon. Hosseinpour (1995) surveys the zoobenthic resources of the Siahdarvishan and Pasikhan, two principal rivers which enter the lagoon. Other entering rivers are the "Bohambar, Chakoor and Esfand".

Forest clearance around the mordab, rice production and other agriculture, dams and weirs on inflowing rivers, river bed erosion through decline in Caspian Sea level, influx of pesticides such as Diazinon (Talebi, 1998), Paraquat, Glyphosite, and chemical fertilisers, domestic and agricultural sewage, excessive aquatic plant growth and natural decay of vegetation (Nezami and Khodaparast, 1996; Filizadeh and Khodaparast, 2005), phytoplankton blooms, some toxic (Nejatkhah et al., 2003) anionic surfactants (Dadaye Ghandi et al., 2005), siltation from deforestation of feeder streams, introduction of exotic species of fish and plants such as Azolla (Iran Daily, 2 November 2006), grazing for livestock, reed cutting for mats, fences and building materials, and a high urban population growth of 4.6% per year, all affect the habitat and the marsh is highly eutrophic. These factors also contribute to the fall in commercial fishing success. In the 1930s the catch was dominated by the valuable Rutilus frisii kutum but in the 1990s the catch was 50-75 times lower and the mordab now has a low value to fisheries. The situation is compounded by the absence of effective fishery management. The introduced Carassius auratus dominates catches. The mordab was a principal breeding ground for Rutilus frisii kutum, Abramis brama and Cyprinus carpio, and to a lesser extent Sander lucioperca, and was an important habitat for Esox lucius. Fish kills occur, more than 100,000 dying in August 1997 due to a lack of oxygen after "torrential rain and the growth of aquatic herbs had created an unsuitable environment" (a Reuters report) and more fish died in 2005 (Iran Daily, 21 August 2005).

The bottom of the shallow west basin was completely covered by perennial submerged vegetation in the early 1970s (Chara, Nitella, Ceratophyllum, Myriophyllum, Hydrilla, and Vallisneria). Water chestnut (Trapa natans) was the predominant floating plant and covered the central basin in 1966. The Caspian lotus, Nelumbium caspium is found all across the lagoon and is a significant part of the standing stock. Phragmites, Sparganium and Typha are emergent plants which engulfed open water. Reeds were formerly cut extensively for building purposes but are now replaced by sheet metal and cement blocks. Falling Caspian Sea water level and eutrophication from domestic sewage and fertilizers aided plant growth. The fern, Azolla filiculoides, was introduced as an additive to cattle feed and rice cultivation from the Philippines in 1986. It soon entered the mordab from the rice fields and mats up to 20 cm thick covered much of the open water in 1991 (Holčík and Oláh, 1992). Dense growths of macrophytes have contributed to declines in commercial fish catches as spawning grounds have decreased, eutrophication is enhanced, and light penetration is decreased and so oxygen declines. There are about 200 sq km of marshes and 30 sq km of shallow open water fed by rivers from the Alborz Mountains. The area of open water in 1989 was only 22.5% of that in the late 1930s (Holčík and Oláh, 1992). However the rise in Caspian Sea level since 1978 has led to a salt water intrusion during the summer months when the Caspian level is at its highest and freshwater input from rivers is at its lowest. Deeper and more saline water may well inhibit plant growth in the future (Khan et al., 1992).

The marsh is only a few metres higher than the Caspian Sea and had a maximum depth of 2.5 m in the early 1970s. Caspian Sea level fluctuations have serious effects on the level of the mordab and hence its utility as a habitat for fishes. The optimum level for the fish industry in general in the Caspian basin is given as -27±1 m (Mandych, 1995). The rise in Caspian Sea level since 1977 is gradually returning the mordab to its supposed, natural brackish state and may improve the fisheries situation which had declined over the last 50 years. Emergent and submergent aquatic macrophytes were decreasing and such fish as Atherina boyeri, Alosa caspia, Liza aurata, Syngnathus abaster and Clupeonella cultriventris were increasing in numbers since 1989. However the fishery will require extensive engineering and management innovations to recover.

Hydrorybproject (1965), Kimball (1973), Kimball and Shayegan (1973), Kimball and Kimball (1974), Hagh-Panah (1992), Holčík and Oláh (1992) and Caspian Environmental Programme (2001c) give details of the limnology of the marsh. Water temperatures vary seasonally from 0° to 28.8°C (average about 16ºC) and dissolved oxygen from 0 to 17.5 mg/l for example. Phytoplankton blooms have killed fish in the mordab, e.g. on 5 June 1997 when dissolved oxygen in the western part was at 0-0.2 mg/l and hydrogen sulphide was at 2.0-2.5 mg/l (Iranian Fisheries Research and Training Organization Newsletter, 17:7, 1997).. Conversely, low phytoplankton populations have probably resulted in lowered fish catches. High water temperatures and chlorophyll inactivation through high light levels reduce the numbers of phytoplankton and hence zooplankton, on which fish feed, also decline. Higgins (1973) found that DDT levels in sturgeon, sturgeon caviar, Cyprinus carpio and Rutilus frisii taken near Anzali were not hazardous to humans in flesh (0.2-1.8 p.p.m.) or in caviar (0.05 to 2.5 p.p.m.), both less than the limit for edible fishes set by the U.S. Food and Drug Administration at 5 p.p.m., but that the level in the caviar was a serious threat to sturgeon reproduction. DDT was more concentrated in the eggs because of their fats and oils in which DDT is more soluble. Certain heavy metals, lead and silver, were potentially harmful to the fishes also. Pourang (1995, 1996), Amini Ranjbar (1998), CEP (2001a) and Sartaj et al. (2005) describe heavy metal concentrations (lead, chromium, copper, cadmium, zinc, manganese and nickel) in fish, surficial sediments and various macroinvertebrates of the Anzali wetland. Levels in Carassius auratus and Esox lucius were below recommended levels for human consumption. Carassius auratus, Cyprinus carpio, Esox lucius and Hypophthalmichthys molitrix in the Anzali Mordab have zinc (5.39-27.98, mean 17.28 p.p.m.), cadmium (0-0.08, mean 0.0251 p.p.m.), cobalt (0-1.67, mean 0.6935 p.p.m.), lead (0.11-2.95, mean 1.04 p.p.m.) and mercury (0.113-0.63, mean 0.3 p.p.m.) in their muscle tissues (Annual Report, 1995-1996, Iranian Fisheries Research and Training Organization, Tehran, p. 46-47, 1997). Nadim (1977) found the highest mercury levels in Caspian Sea fish were 0.51 and 0.36 mg/kg in Rutilus frisii and Esox lucius respectively with the lowest in Liza aurata at 0.07 mg/kg. As the acceptable limit was 0.5 mg/kg, mercury contamination in fish was not considered a problem. The lowest zinc concentration was in H. molitrix, the highest lead concentration was in C. carpio and the highest cobalt concentration in C. auratus but concentrations were less than those set by WHO as significant. Södergren et al. (1978) reported on pollution with organochlorines in Esox lucius from the mordab and found this predatory fish to have accumulated the DDT metabolite p,p^'-DDE, suggesting that this occurred over considerable time and was not a recent event. DDT did not appear to be incorporated in the pelagic food chain, although it has been used for agriculture and vector control problems. Most DDT probably attaches to clay and soil particles and settles out on the mordab bottom. These authors also recorded DDT from sturgeon species and their eggs in Iranian waters. Pollution continues to be a problem in this heavily populated, industrial and farming region. Heavy rains in October 1995 swept industrial wastes including heavy metals such as lead and zinc, agricultural waste and domestic sewage into the mordab. A fish kill resulted as evidenced by the mordab being covered with floating dead fish. The kill was attributed to the heavy metals and to oxygen depletion (http://netiran.com:80/news/IRNA/html/941029IRGG01.html).

Amini Rad (2001) assesses the socio-economic importance of fisheries in Bandar Anzali. Fishes are very popular food items there with an average consumption of 11.3 kg, 70% more than in the rest of Iran. White fish (safid mahi, Rutilus frisii) was 1.5 times more expensive than mullets (Mugilidae), 2.6 more than other species and almost 28 times kilka.

Gorgan (= Asterabad or Astrabad) Bay (36°40'N, 53°50'E) is 56 km long by 16 km long and is brackish (8.7-10.0‰) because of input from rivers although Bayrami et al. (20030 give 16 p.p.t. The bay encompasses about 400 sq km. A general description is given by Zanusi (1995) who considers it to be the second richest resource for caviar in the Caspian Sea after the Volga River. The Caspian Environmental Programme (2001c) gives an average surface water temperature of 19.1ºC, oxygen from 2.4 to 11.1 mg/l, pH 8.0-8.5 and total dissolved solids 11.23 mg/l in February to 15,052 mg/l in March. The bay's ecology has been changed by the recent rise in sea level which resulted in storm surges over the sand bar between it and the Caspian Sea. The construction of the Voshmgir Dam on the Gorgan River in 1970 also had an effect, reducing the amount of fresh water to the river mouth which provided spawning areas for Cyprinus carpio and Rutilus rutilus. Over 40% of the total sturgeon fishing in the Caspian Sea is centred on Bandar-e Torkeman. There is also a black market in sturgeon products. Authorised fishing resources shrunk by 33% from 1993-1994 to 1994-1995 through unauthorised fishing, lack of controls and decrease in controlled sturgeon reproduction. The authorised catch in 1994 for the region from the Neka River to the Turkmenistan border was 1500 tonnes and the unauthorised catch was probably of similar size. The caviar production was 57,000 kg.

The bay once had a valuable Rutilus rutilus fishery with an annual catch of 4000 t per year about 20-30 years ago but this has disappeared (Petr, 1987). The bay is now dominated by Mugilidae (CEP, 1998). The catch in the Voshmgir reservoir was 60 t in 1986 although it may improve with stocking programmes. Lalouie (1993) surveyed the hydrobiology of the bay and found an average pH of 8.3, similar to the sea proper as were alkalinity and total hardness. Water temperatures ranged from 5°C to 30°C annually. Pollution from urban and industrial sewage and pesticides is present.

Gorgan Bay is believed to be an important nursery ground for Liza aurata, a major food fish, although an exotic. Cage and pen culture operations in the bay may result in escapes of exotics that could affect native species. On three separate occasions, cages capsized in storms releasing millions of Oncorhynchus mykiss fingerlings (www.ramsar.org/ram_rpt_37e/htm, downloaded 4 May 2001).

The area of the Miankaleh Peninsula, Gorgan Bay and the nearby freshwater Lapoo-Zaghmarz Ab-bandans is designated as a Ramsar Site (World Conservation Monitoring Centre, 1990). The Miankaleh Wildlife Refuge encompasses 81,180 ha and is part of the Miankaleh Protected Region (97,200 ha). Jones (www.ramsar.org/lib_dir_2_3.htm downloaded 14 April 2000) gives 68,800 ha for the Wildlife Refuge. The Miankaleh wetland may encompass 40,000 ha, not the larger figures as originally designated (Khan et al., 1992). The bay has a sand and mud bottom and is oligotrophic. There are extensive marshes along the southern and eastern shores which flood in fall and winter. These marshes are eutrophic from agricultural runoff and stream and irrigation channel inputs. The bay vegetation comprises principally glasswort (Salicornia), sedges (Carex) and rushes (Juncus) with some small reedbeds of Phragmites communis. The ab-bandans have extensive reedbeds of Phragmites communis with stands of reedmace (Typha) and abundant submerged vegetation. Several factors will affect the ichthyofauna including irrigation requirements limiting freshwater flow into the bay and ab-bandans, a fish processing plant at Ashuradeh with associated wastes, a new road along the peninsula which facilitates access and potentially increased pollution and poaching, reed cutting, heavy livestock grazing, agricultural wastes, aquaculture ponds using exotics, fishing by local people and a proposed nuclear power plant. The whole area is an important nursery and breeding ground for fishes. The ab-bandans are not protected although they are within the Ramsar Site. The two shallow ab-bandans occupy 950 ha at 36°50'N, 53°17'E northwest of Behshahr. They are fed by irrigation ditches and drain east into Gorgan Bay.

The Gomishan Marshes at 37°15'N, 53°55'E extends along the eastern shore of the Caspian Sea from Gomishan north and northwest to the Turkmenistan border. There are about 4850 ha of brackish lagoons and marshes, their brackish nature occasioned by the rise in Caspian Sea level. There is agriculture, livestock grazing and waterfowl hunting. The fish fauna is mostly unknown but the area is probably and important breeding ground for the commercially important mullet Liza aurata (www.ramsar.org/ram_rpt_37e.htm, downloaded 4 May 2001), for Rutilus rutilus and for Sander lucioperca, and the latter two are open to hydrocarbon pollution (Ghasempouri and Esmaili Sari, 2002).

The Astara lagoon at the western end of the Caspian coast of Iran is separated from the Caspian Sea by a sand bar, and is flooded across this bar during winter storms. The lagoon encompasses about 950 ha and is fed by a river during August to March, reducing its salinity to about 7 p.p.m. There is a rich growth of aquatic plants and the area has potential for fishing and aquaculture (Petr, 1987). Lavandavil Marsh at 38°20'N, 48°50'E is found about 10 km south of Astara and lies within a Protected Area of 949 ha. It is a small swampy woodland and freshwater marsh with extensive stands of Juncus. Abbasabad Dam at 38°23'N, 48°50'E south of Astara is a 45 ha water storage reservoir. Nur or Neur Gol at 38°00'N, 48°33'E in the northwest Alborz Mountains is a 200 ha freshwater lake at 2300 m about 50 km south of Astara. It lies within the Lisar Protected Area which includes the whole watershed of the Lisar River. The lake drains north to an Aras River tributary but freezes over for about 6 months each year. The submergent vegetation is rich. Rainbow trout (Oncorhynchus mykiss - see account of this species) were introduced to the lake in the early 1970s in an attempt to start a sport fishery. There is also a number of permanent and seasonal lakes along the Sabalan Mountain range which lies partly in this basin and partly in the Lake Orumiyeh basin and these are known to have fishes (www.netiran.com, downloaded 17 June 2004).

The "Lapu" Lake, about 20 km northeast of Sari in Mazandaran, is an example of a smaller water body along the Caspian shore, covering about 100 ha with a maximum depth of about 2.5 m, perhaps 3.5 m in winter (Petr, 1987). There is a rich assortment of aquatic plants. In 1985, 90,000 fingerlings of common carp or kopur (Cyprinus carpio), grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) were stocked and 120,000 fingerlings were added in 1986. A good harvest was reported in 1986. There is a wide variety of reservoirs on the Caspian shore, varying in size from about 10 to 400 ha. Some completely dry out in summer when water demands are high but others are stocked with common carp, silver carp and, to a lesser degree, grass carp. There are also populations of native fishes such as kopur Cyprinus carpio and ordak mahi (Esox lucius) but not in commercial quantities.

The "Amirkelayeh" Lake or Lagoon is located between the cities of Lahijan, Langarud and Kiashahr at 37°17'N, 50°12'E. It is an example of a larger, freshwater lagoon as it encompasses 1230 ha, being 4.5 km long and up to 1.7 km wide. The lake is in the Amirkelayeh Wildlife Refuge and is a Ramsar Site (World Conservation Monitoring Centre, 1990). Average depth is only 1.6 m although some areas reach 4 m (Scott (1995) states 3-4 m on average but up to 6 m). The lake is fed by springs and precipitation and is eutrophic. It lies above the 1980s rise in water level of the Caspian Sea (Khan et al., 1992). It may flood into marshes or the Caspian Sea via a small stream into a channel of the Safid River but is above the recent (1990s) rise in Caspian Sea level. Vegetation is Phragmites communis and Typha with abundant submerged and floating plants such as Nelumbium, Lemna, Potamogeton, Hydrilla, Myriophyllum and Ceratophyllum. The fishes comprise Esox lucius, Sander lucioperca, Carassius sp. (listed as Crucian carp, probably C. auratus), Blicca bjoerkna, Syngnathus abaster, Pungitius platygaster, Silurus glanis, Rutilus rutilus, Cyprinus carpio, and Tinca tinca. Ctenopharyngodon idella has been introduced (Nejatsanatee, 1994).

The Fereidookenar or Fereydun Kenar Marshes at 36°35'N, 52°31'E lie 13 km southwest of Babolsar and occupy 1000 ha. These marshes are artificial, being a damgah or shallow impoundment for duck hunting and water storage. They are one of the best protected wetlands along the Caspian shore as the local duck hunters aggressively restrict access (Khan et al., 1992). There are fringing reed beds of Phragmites australis and Typha with abundant floating and submerged vegetation.

"Seyed Mohalli, Zarin Kola (both at 36°44'N, 53°00'E) and Larim Sara (36°45'N, 53°03'E)" are ab-bandans and associated marshy areas found north of Sari and east of the Tajan River mouth. The first two occupy 600 ha and the last one 1000 ha. Aquatic vegetation is rich, both submerged and floating, and there are extensive stands of Typha and Phragmites. Construction of a large dam on the Tajan will result in an associated network of irrigation canals which may cause ab-bandans to be neglected. The ab-bandans, although artificial, have more of the character of a natural marsh than irrigation channels. Much of this area of the coastal plain has been converted to agriculture which destroys natural wetlands so ab-bandans take on a disproportionate importance as a refuge for wildlife including fishes.

Various dams have been built or are under construction in this basin including the Gourchye Embankment Dam 15 km southeast of Ardebil with a capacity of 20 million cu m, the Yamchi Dam 20 km southwest of Ardebil and the Gaybeglou Dam 40 km south of Meshgin Shahr in East Azarbayjan Province, the Maku Dam with a 150 million cu m capacity in West Azarbayjan and the Agh Chay or Ziaeddin Dam near Khvoy (http://netiran.com/news/IRNA/html/950914IRGG06.html; http://netiran.com/news/IRNA/html/950914IRGG10.html; http://netiran.com/news/IranNews/html/96102201INEC.html). The Neka Power Plant in the eastern Caspian basin entrains a large amount of debris and algae that prevent effective physical systems of fish protection from entrainment. An electrical fish protection system is used instead. Inflatable rubber dams are now being constructed in the lower reaches of rivers, e.g. the Babol, to block the rise in Caspian Sea level such that agricultural water intakes will not be contaminated with saline water. The effects of these dams on fish migrations and biology is unknown (www.satujo.com/english/barrage/dams4.htm, downloaded 20 December 2002).

Qanats and springs are not a feature of this basin as in so many other parts of Iran, except for the drier areas drained by the Qezel Owzan and other streams of the plateau and in the drier valleys of the east away from the rainfall of the Alborz-backed Caspian lowlands. One particular artificial habitat for fishes in the lowlands are the ab-bandans, shallow freshwater marshes maintained as habitat and overwintering areas for waterfowl and for conserving water for rice fields (Beaumont and Neville, 1968). Some ab-bandans around the Anzali Mordab were set aside as refuges for waterfowl and incidentally would protect some fish species threatened by the draining of marshes. Construction of irrigation dams will also lead to abandonment of ab-bandans. Ab-bandans and damgah (ponds made specifically for duck trapping) have declined in number but still encompass 10,000 ha (Scott, 1995).

Extensive stocking of commercially important species in the sturgeon (Acipenseridae) and carp (Cyprindiae) families takes place annually in the Caspian waters of Iran. These are detailed under the species accounts. Varedi and Fazli (2005) examined the rivers Shirud, Tonekabon, Larim, Tajan and Goharbara of Mazandaran for the physico-chemical properties of estuarine water in 2000-2001. Only the Shirud and Tonekabon met U.S. Environmental Protection Agency standards for release of fingerlings, the other rivers failing because of water abstraction and improper land use development.

Introduced species based on a summary by Mamaev (2002) include Liza aurata and L. saliens (Mugilidae), Platichthys flesus (Pleuronectidae, apparently not surviving), Psetta maxima maeotica (Scophthalmidae, as Rhombus maeoticus in TACIS (2002) and probably not surviving), Scomber scombrus (Scombridae, not often recorded elsewhere in the literature (an example is TACIS (2002), probably not surviving), Engraulis encrasicholus (Engraulidae, probably not surviving), Anguilla anguilla (Anguillidae), Gambusia affinis (Poeciliidae), Oncorhynchus keta , O. kisutch, O. gorbuscha and Salmo salar (Salmonidae), and Ctenopharyngodon idella, Hypophthalmichthys molitrix, H. nobilis (Cyprinidae).

Zoogeographically, Berg (1940) considers this part of Iran to belong to the Kura-Iranian sector of the Caspian District of the Ponto-Caspian-Aral Province. This fauna is very similar to that of the Kura River although certain genera are absent, even in the Safid - a major river, such as Chondrostoma, Gobio and Leucalburnus.

Dasht-e Kavir

This basin occupies an immense area of north-central Iran, over 200,000 sq km in the rain shadow of the Alborz Mountains. Mahdavi and Anderson (1983) detailed the qanat water supply of the margins of this basin. Intermittent streams drain to several kavirs which are grouped together under this basin for convenience. The principal kavirs are the Damghan Kavir in the north, the Sabzevar Kavir in the north-east and the Kavir-e Bozorg (or Great Kavir) occupying much of the basin, being about 450 km in east-west extent and 250 km in north-south extent. The Kavir-e Bozorg receives waters exiting from other kavirs. The principal streams entering this basin drain the Alborz Mountains and their eastern extensions in Khorasan. The Alborz peaks exceed 4000 m and even to the east the Kuh-e Binalud (36°30'N, 58°55'E) attains 3416 m near Neyshabur (36°12'N, 58°50'E) while the lowest points are at an altitude of 650 m. The Damghan Kavir receives two major streams from the Alborz, the Damghan River and the Hasanabad River, and other streams dry up in early summer. The Sabzevar Kavir has numerous small and temporary streams which feed it as well as two major streams, the Mureh River, 320 km long, and its tributary, the Kalshur River, 240 km long. The Kalshur drains the Kuh-e Binalud and flows west to meet the south flowing Mureh. These rivers drain areas rich in salt domes and samples taken show water to be saline and some streams are fishless. Qanats support fishes in this area although the fish only emerge at night in some cases. Ruttner-Kolisko (1964; 1966) and Ruttner and Ruttner-Kolisko (1972; 1973) studied the chemistry and limnology of natural springs and qanats in a mountain area separating this basin from the Bejestan basin. Several factors were found to affect the limnology. Climatic factors were temperature, precipitation and evaporation, edaphic factors were geology, salt content of soil and intensity of waterflow, and pollution by man and animals was a factor. There was a range in salinity from low (<15 mval/l) to high (>120 mval/l). Qanat discharges in this area were 20-50 l/sec. Springs were small and many were dammed to form small pools for livestock.

These large central basins of Iran were once thought to be desiccating lake basins. However more recent studies have shown that although there may have been shallow lakes, e.g. saline Lake Damghan, and rivers carried more flow and were perhaps more closely linked than today, there was no extensive and continuous freshwater lake over the whole of central Iran that could have facilitated fish dispersal. While the hills received increased rainfall, the central deserts remained arid during Pleistocene "pluvials" and cold phases (Bobek, 1959; Scharlau, 1968; Krinsley, 1970).

Dasht-e Lut

The Lut basin of south-central Iran is ringed by mountains yet has the lowest point on the plateau at 205 m in the Namakzar-e Shahdad. The central portions of this basin are some of the most barren and inhospitable in Iran or indeed the world. Conrad and Conrad (1970) and Gabriel (1938) give descriptions of this desert basin. Intermittent streams drain the mountain ranges around Kerman east to the namakzar or namaksar (= salt waste), north from mountains near Bam (29°06'N, 58°21'E) such as the Kuh-e Jebal Barez (28°30'N, 58°20'E) and Kuh-e Bazman (28°04'N, 60°01'E) which delimit the northern edge of the Jaz Murian basin, west from the slopes of the active volcano Kuh-e Taftan (28°36'N, 61°06'E) and south from the mountain ranges near Birjand (32°53'N, 58°13'E). High points include the Kuh-e Hazaran west of Bam and south of Kerman at 4402 m. Such heights retain snow and have more abundant precipitation which feed streams at least in the mountains. However many minor and some apparently major streams marked on maps are completely dry. Much of the water is absorbed into the ground and tapped by qanats. The Shah River at Birjand is dry through most of the year (Fisher, 1968). Tabas (33°36'N, 56°54'E) at the northern end of this basin has numerous qanats (Krinsley, 1970) but I have not seen samples from this area.

The Tahrud is an important stream which drains the Hazaran to a small sump in the south of the Lut basin and has a continuous flow which becomes subsurface well east of Bam (compare maps). Its maximum map extent approaches 250 km. In the mountains, the Tahrud is 1-8 m wide and up to 50 cm deep. Water temperature was a warm, 15°C on a cool December day.

The Lut includes the largest sand dune field in Iran (ca. 10,000 sq km) which has developed through aeolian erosion. Sand dunes block roads and may well fill in or divert streams.

Qanats in this basin can have water temperatures much higher than the few surface streams. One qanat near Bam had a temperature of 25°C in a snowstorm, yet stream temperatures below 10°C are not uncommon.

Esfahan

The principal feature of this basin is the Zayandeh River which rises in the Zagros Mountains east of Zard Kuh at 4548 m (32°22'N, 50°04'E) and flows east for about 300 km to its terminal basin, the Batlaq-e Gavkhuni at 32°20'N, 52°47'E, a salt marsh with a salinity of 315‰ (Löffler, 1961) and an average depth of about 1 m (www.netiran.com/php/artp.php?id=1615, downloaded 19 July 2004). The salt marsh can dry up in summer. Wetlands associated with the terminal basin are a Ramsar Site of 43,000 ha (or 37,000 ha; sources vary as does the size of the marsh seasonally and annually). Associated marshes at the river delta and along its banks are fresh to brackish. These marshes are fed by flooding and by irrigation canals but dry up in late spring or early summer. Flooded areas often freeze over in winter. There is little natural marsh vegetation and flooding occurs over degraded steppe and cultivated land. Water is diverted for irrigation and for domestic and industrial uses. It  receives pollution from Esfahan and other urban sources. Esfahan is a major oasis city on the Zayandeh at 32°40'N, 51°38'E with a population over 1 million.

The Zayandeh basin encompasses about 30,480 sq km and is connected to the upper Karun River basin (which drains to the Persian Gulf) by the Kuhrang Tunnel constructed in 1953 although first proposed in the early sixteenth century (Fitt, 1953; Afifi, 1966; IRNA, 5 February 2002). Two additional tunnels are under construction (Stoltz, 2002). A hydroelectric dam at Godar-e Langar (also known as Karun-4) would also supply piped water to Esfahan 300 km away if it is completed (Whitley and Gallagher, 1995). Dams have deleterious effects on a riverine fish fauna and are often stocked with exotic species. The upper Karun has not been well explored for endemic taxa. Mean annual flow of the Zayandeh is estimated at 1.2-1.45 billion cu m, used mostly for agriculture but an increase in population and industry has necessitated dam construction (Shah Abbas Kabir or Sadd-e Zayandeh Rud, capacity 1450 million cu m) and diversion schemes. There is also the Hana Dam on the Hana River at Semirom with a height of 35 m and a capacity of 45 million cu m (http://netiran.com/news/IRNA/html931003IRGG04.html) and the Izadkhast dam to the southwest of the Batlaq-e Gavkhuni (www.irna.com/newshtm/eng/12003142.htm, IRNA, 2 July 2000). As well as man-made diversions, the upper Zayandeh basin has captured headwaters from systems tributary to the Persian Gulf. The Shah Abbas dam has reduced the natural flood flows downstream and little water now enters the salt desert.

Plans have been made to transfer Zayandeh River water from the Band-e Cham-e Asseman to Yazd's Shahneh Reservoir by pipeline over a distance of 375 km (Hamshahri, Tehran, 629:5, 22 February 1995). 78 million cu m of water will be transferred annually and this will decrease the habitat for fishes in the Zayandeh River basin.

Spring flow is at least 1700 cu m per second, but this drops to 28 cu m per second in autumn (Oberlander, 1968b). Discharge peaks in April with low values in September-October and decreases dramatically downstream after abstraction, evaporation and infiltration (Beaumont, 1981). The Zayandeh can be forded on foot at Esfahan in summer and Buckingham (1829) reported it to be dry. It dried again in 2000, 2001 and 2003 under drought conditions, partly through water abstraction upstream for irrigation and partly through aqueducts to other desert cities (Rafsanjan and Yazd) not in the Esfahan basin (Anonymous, 2001b; Foltz, 2002; newspaper reports). The river is polluted by city sewage, local wastes dumped directly into the river, and industrial wastes (Moghadam, 1976; Al-Hashimi, 1987; Tehran Times, 15 September 1997). 172,000 cu m of industrial pollutants enter the river daily. Pollutants include phosphorus, nitrogen, lead, nickel, zinc, organic substances, iron, manganese, oil products, mineral and organic dyes and the sewage from villages with a population of 900,000 people. Nadim (1977) found the highest mercury levels in fish were 0.19 mg/kg. As the acceptable limit was 0.5 mg/kg, mercury contamination in fish was not considered a problem. The flow is 1.45 billion cu m annually of which 1.1 billion cu m is used for agriculture, 150 million cu m for industry and the remainder is used as drinking water. The basin has a high demand for water supplies and has been under stress in this regard for the last 50 years. It will be unable to meet water demands in less than 15 years (Salemi and Heydari, 2006).

Ouseley (1819-1823) noted numerous small "bleak" and caught several carp-like fish up to 12-14 inches long (ca. 30-36 cm) in the deeper waters around the bridges over the Zayandeh at Esfahan.

The Batlaq-e Gavkhuni and marshes on the lower Zayandeh are a Ramsar Site, the lake occupying 12,000 ha, permanent marsh 1000 ha and temporary marsh 30,000 ha (World Conservation Monitoring Centre, 1990) or 47,000 ha (Mehrabi, 2004). It lies at 1470 m and has an average depth of 1 m. The Batlaq (= salt lake or marsh, gavkhuni = cowshed because cattle are put out to pasture in the marshes) is fishless but the marshes have a freshwater character depending on the input from the Zayandeh River. The substrate is silt and mud. Much of the marsh has been converted for agriculture. Flooded areas may freeze over in winter. The salt lake is said not to dry out completely (Mehrabi, 2004) although flows were down to 10-100l/s in the dry years 2000-2002 and the lake was dried out (Esteky, 2006).

As with all plateau basins, this one also has springs and qanats which contain fishes. Surber (1969) gives some data on total alkalinity and calcium-magnesium hardness in this basin and characterises it as moderately hard.

Fish farms have been developed in Esfahan Province (Tehran Times, 31 October 1999). Thirteen cold water and 10 warm water fish farms are expected to yield 490 t of fish, rising to 18 cold water and 15 warm water farms by the year 2000 with a yield of 760 t.

Hamun-e Jaz Murian

The Hamun (= marshy lake, in this instance) is dry for most of the year, but fills with fresh water in winter (Harrison, 1941). Its extent is presumably variable, depending on rainfall. It lies at an altitude of about 300 m, with a still-subsiding depression within the Jaz Murian plain, and is ringed by mountains.

The two major rivers flowing into the Hamun are the Halil (or Haliri) River, known as the Kharan or Zar Dasht River in its upper reaches, which flows from the neighbourhood of Kuh-e Laleh Zar at 4374 m lying to the northwest, and the Bampur River which flows towards the Hamun from the east but follows a southerly course in its upper reaches (Tipper, 1921). The source of the Bampur River lies between 1000 and 1500 m. The Halil is a longer river (ca. 390 km) than the Bampur (ca. 315 km) with a stronger and more continuous flow. There is a 130 m high dam on the Halil, the Jiroft Dam, 40 km upriver of Jiroft. A flood water storage dam at Bazman is 37 m high with a capacity of 3.3 million cu m (www.irna.com, downloaded 26 January 2003). Discharge is only 1-3 m³/second in summer. Floods occur (including an historical one which destroyed Jiroft in 1000 A.D., and one in 1993) and river discharge can reach 800 m³/second in 15 hours with an 18 m rise in reservoir level in 40 hours and massive sediment transport with turbidity reaching 280 gr/liter (sic) (www.stucky.ch/publication/JIRFLOOD.htm downloaded 19 July 1999). The Bampur River in late November and early December was flowing in its upper reaches near Karevandar and around Iranshahr and Bampur but was dry between these two areas. Judging from its width and depth below Bampur it probably did not reach the Hamun by surface flow. Most rain at Iranshahr falls in January and February (15 and 52 mm respectively) with none in the remaining months except for rare summer monsoonal rains (Ganji, 1960). Irrigation and canal schemes in the Bampur basin suffer from erosion and siltation problems as elsewhere in Iran (Borowicka, 1958).

The Jaz Murian basin is ringed by much smaller streams draining the surrounding mountains. These are all very small, e.g. the Ughin River was as narrow as 30 cm and maximum depth in pools was about 50 cm when sampled on 4 December 1977.

Hamun-e Mashkid

The Hamun-e Mashkid (= Mashkel) lies within Pakistan with its western edge on the border with Iran. In this instance hamun means a salt waste. The mountain ranges in this area of Iran are parallel with the Iran-Pakistan border and run in a northwest-southeast direction.

The Mashkid River rises to the east of the mountains ringing the Hamun-e Jaz Murian basin and flows east into Pakistan where it receives a right bank tributary, the Rakhshan River, before turning north to flow into the Hamun-e Mashkid. Its total length is ca. 430 km. Two tributaries of the Mashkid within Iran are the Rutak River and the Simish (= Sunish River) which drain the lowlands between Kuh-e Birag (27°35'N, 61°20'E) and the Badamo Range (27°38'N, 62°08'E) from the northwest to enter the Mashkid River southeast of Saravan (27°22'N, 62°20'E). The upper Mashkid River is a small mountain stream, probably with a perennial flow. The lower reaches of this river, and of the Simish, comprise a series of muddy pools of varying size. Some of these pools were isolated and fishless in early December 1977, while larger ones, perhaps 1 km long, contained some emaciated specimens. In this area fish are found more abundantly in perennially flowing qanat streams.

The Tahlab River and its tributaries drain the eastern slopes of the mountains south of Zahedan. The Tahlab flows in a southeasterly direction into the Hamun over a ca. 160 km course. It was dry between Zahedan and Mirjaveh (29°01'N, 61°28'E) in early December 1977. The Ladiz River is a short (ca. 80 km) right bank tributary of the Tahlab flowing from Kuh-e Taftan. In its lower reach it was a small stream flowing in the bottom of a deep and wide canyon. The stream banks were white with salt deposits.

Kor River

This basin occupies 26,440 sq km north and east of Shiraz at a lowest altitude of ca. 1525 m. Its lowest part is occupied by a chloride lake, the third largest lake in Iran, composed of two parts, a northern basin known as Narges or Tashk and a southern basin known as Neyriz = (Niriz) or Bakhtegan. The two basins are not always connected and the southern basin is saltier because major freshwater input is from the north. Löffler (1956; 1957; 1959; 1968; 1981) gives details of this lake. The lake area varies between 1210 and 2400 sq km, with a maximum depth of 1.1-1.7 m and a mean depth of 0.5 m. Salinity is 13.7-101.6 gl^-1 and temperatures range from 15°C to 45°C in the shallows. The lake is reported to have dried out completely in 1871, 1933 and 1966 (Cornwallis, 1968a) and in 2000 (www.irna.com/newshtm/eng/05142727.htm, IRNA, 26 July 2000). Löffler (1993) considers that this lake may dry out permanently in the near future if abstraction of water from the Kor River for irrigation continues to grow. The drought in 2003 reduced Lake Bakhtegan to a series of puddles. Fluctuations in lake levels affect the freshwater faunas of springs, including fishes, which drain into the lake: high levels swamp the springs with water too saline for fishes to survive. Low levels, however, allow streams to connect and exchange faunas on the lake bed so they are not as isolated as they might appear.

Bobek (1963) suggests that there may have been an outflow from this basin to the Gulf at the south-east corner of the lake which was cut off at the end of the Pleistocene by alluvial fans. However Krinsley (1970) maintains that any outlet was closed by the late Pliocene.

Major rivers are the Kor (= the classical Araxes) and its tributary the Pulvar (or Sivan) (= the classical Medus) which rise in the Zagros Mountains to the north and north-west and drain to the north-west corner of Lake Tashk. These mountains are high enough (Kuh-e Dinar at 4432 m and 30°50'N, 51°35'E) to have a snow cover and thus there is a continuous flow throughout the year. However in summer water does not reach the lake because of the demands of irrigation. Drainage and irrigation canals run through the basin on the plains at the north end of the lake. Several springs feed marshes, notably the Lapu'i marshes, a wetland of 150 sq km to the north-west of the Kor-Pulvar junction, the Zarqan marshes of 4 sq km, an extension of the Lapu'i marsh (both now severely damaged by construction of a drainage canal as part of the Dorudzan or Sadd-e Daryush-e Kabir (dam) at 30°15'N, 52°20'E, a project on the Kor River), the "Gomun", "Gumoon", "Gumoo" or "Sangare" marshes of 2 sq km at the north-west corner of Lake Tashk and the Sahlabad marshes of 5 sq km on the south-east coast of Lake Bakhtegan (Cornwallis, 1968a; 1968b). The Band-e Amir or Kamjan Marshes at 29°40'N, 53°05'E are formed at the delta of the Kor River and encompassed about 100 sq km but the Daryush-e Kabir Dam severely restricts the water flow to these marshes. A dam on the Bolaghi Gorge is proposed which would affect the flow of the Pulvar but is being opposed on archaeological grounds (www.netiran.com, downloaded 4 October 2004).

The fish, Aphanius sophiae, is found in these marshes and springs, but suffers predatory attacks in an unusual way. The greater flamingo stirs up mud in its feeding and this releases H₂S, CO₂, and CH₄, suffocating the fish and making them easy prey for herons.

The Neyriz Lakes and Kamjan Marshes are a Ramsar Site (World Conservation Monitoring Centre, 1990; Khan et al., 1992) although the Kamjan Marsh area may be deleted because of drought and other factors such as rice, wheat and cotton growing and livestock grazing. The "Cheghakhur" and "Gandoman" marshes in Chahar Mahall and Bakhtiari Province will be substituted for the Kamjan Marshes as a listed Ramsar Site (Khan et al., 1992). The "Gumoon" marshes have been partially drained for irrigation and for conversion into aquaculture ponds (Khan et al., 1992).

The Daryush-e Kabir Dam on the Kor River contains 990 million cu m of water, is 24 km long and about 9.5 km wide. Its conductivity is 363 µS compared to Lake Bakhtegan at 105,900 µS and consequently it can support a fish fauna. Band-e Amir on the Kor River is a diversion dam over 1000 years old and also provides a small reservoir habitat for fishes (Houtum-Schindler, 1891). At least three other dam sites have been proposed in this basin (Tang "Boraghi" (= Tang-e Boraq), "Tang Bulak" and "Ghaderabad" (= Qaderabad)). Surber (1969) gives some spot data on pH, total alkalinity, calcium-magnesium hardness, chlorides and free CO₂ in this area. Water is relatively hard. Concentrations of total dissolved solids vary between 202 mg/l and 436 mg/l in the rivers compared to a range of 333-6937 mg/l in the Gulf basin.

Kaftar Lake at 30°34'N, 52°47'E is at ca. 2300 m in the Zagros Mountains northeast of Shiraz. It occupies 4700 ha (500 ha in Khan et al. (1992)) and is a shallow, semi-permanent freshwater lake which can dry out completely in summer and is frozen over in winter. The annual mean water temperature is 14.4°C, the mean maximum 23.5°C and the mean minimum about 2°C (B. Jalali, pers. comm., 1999). Lake water has been proposed for irrigation usage in the past and a recently proposed earthen dam would reduce the lake area by half (Scott, 1995). It has a mixed ichthyofauna of native species and exotics. The fishes recolonise from springs and the main river entering the lake and are also stocked.

The Kor River basin also contains qanats. Some of these flank the Pulvar River, for example, and serve to bring water to fields above the incised river bed.

Pollution in this basin has been recorded by Merchant and Ronaghy (1976) where industry discharges waste untreated into surface and ground waters. Waste from a sugar mill killed 1 million fish in 1994 and a further 500,000 fish died in 1996 from industrial waste (http://www.iran-e-azad.org/english/noi/noi-83.html or News on Iran, 83, 15 November 1996). A fish kill was reported from the Pulvar River in 1978, polluted by wastes from a food factory (Coad, 1980c). Peritore (1999) and Moussavi and Saber (1999) record the Kor River receiving organic wastes from animal processing plants, ammonium and mercury from petrochemical complexes and such heavy metals as cadmium, chromium and arsenic from electronics manufacturers. Ebrahimi et al. (2008) report lead levels in Cyprinus carpio and Capoeta spp. to be less than the maximum allowable by the European Union but still of concern.

Channels started in 1981 to provide more agricultural land drain through the Kamjan Marshes to Lake Tashk and the Kharameh Marshes to Lake Bakhtegan. Much of the marsh habitat has been destroyed. The "Gumoon" Marsh has been drained for agriculture and fish ponds.

Miller (1985) reports on deforestation in this part of Iran during the fourth to second millennium B.C. Even marsh areas were probably treed before demands for charcoal and construction materials increased. The fish faunas must have adapted to increased insolation and any species sensitive to higher marsh and stream temperatures would become less common.

Lake Maharlu

The Maharlu basin is the valley of Shiraz (29°36'N, 52°32'E) and encompasses about 4100 sq km. Lake Maharlu is at an altitude of about 1460 m, has an estimated average area of 220 sq km, a maximum depth variously cited as 0.5 and 3 m, a salinity of 124‰ or 304.95 gl^-1 and is fishless. The lake dried out completely in 1967 (Cornwallis, 1968a). The lake is fed by minor streams and springs around its margin. The stream flowing through Shiraz is dry for much of the year or composed mostly of polluted wastes. The basin also has a number of qanats. Stream temperatures vary between 8°C in January to 32°C in June while qanats can be warm, e.g. at Sarvestan (29°16'N, 53°13'E) in December a qanat was 25°C. Surber (1969) gives some spot data on pH, total alkalinity, calcium-magnesium hardness, chlorides and free CO₂ in this area.

The basin is separated by only a small rise from the Mand River of the Gulf basin, but is treated separately here because fish collections have been focused on this valley as Shiraz is the major city of southern Iran.

Major fresh to brackish springs and their associated marshes (Ab-e Paravan (2.5 sq km), Barm-e Shur (1.5 sq km) and Soltanabad (7 sq km)) are concentrated at the northern end of the lake (Cornwallis, 1968a). Larger springs have pools which are about 2 m deep and reed beds of Phragmites and Typha, some of which are cut. Livestock grazing occurs. Amphibious tanks were tested in Barm-e Shur, stirring up anoxic bottom mud and leading to a fish kill.

Numerous small springs around the lake are isolated from one another by the intervening hypersaline water. Lake levels fluctuate markedly and allow streams to meet on the exposed salt flat when the water level is low. At high levels, salty water invades the lower springs and eliminates their fishes, which only recolonise when the lake level falls again and connection is made with a stream from a spring which was above the last rise in lake level. One spring had a salinity of 34‰ at the source when the lake had risen to "invade" the spring. Aphanius persicus were concentrated close to the source but would attempt to evade capture by swimming into the salt lake where salinity was 180‰. Their excursions into water of this salinity was brief and fish paled visibly while darting in and out. Another spring was replete with tooth-carps at 144‰. Temperature on 8 June 1976 at one spring was 27°C at the surface and 32°C on the bottom, at about 1 m depth.

Lake Orumiyeh

Lake Orumiyeh (= Reza'iyeh, Urmia, Urmi, Urumiyeh or Darya-e Shahi) lies in north-west Iran and is the only Iranian lake large enough to appear on general maps of the world. This lake is a Ramsar Site and includes Orumiyeh National Park. Brackish marshes in the northeast, northwest and southern shores probably support some fishes but the lake itself is too salty.

Orumiyeh lies at about 1275-1300 m (accounts vary), is about 128-149 km long and 40-60 km wide. This thalassohaline lake has a surface area of 4750-6100 sq km, a volume of 29.4 cu km, a mean depth of 4.9-6.0 m, a maximum depth of 16 m, and a temperature range of -1.3-27.5°C. Lake level can rise as much as 2 m in one season, as it did in the winter of 1968-1969. It is a sodium chloride-sulphate system with a salinity up to 310.79 gl^-1 (but mostly 217-235gl^-1) and consequently is fishless (Abich, 1856; von Seidlitz, 1858; Rodler, 1887; De Mecquenem, 1908; Plattner, 1955; Vladykov, 1964; Kelts and Shahrabi, 1986; Ghaheri et al., 1999; www.neda.net/inwm/no.6/english/geology/geology01.html, downloaded 10 July 2000; Van Stappen et al., 2001; Eimanifar and Mohebbi, 2007). Initially the lake was probably fresh (Admiralty Naval Staff, 1918). A causeway has divided the lake into two parts since 1989; a gap allows a limited exchange between the two parts. Its drainage basin approaches 57,000 sq km (or 51,786 sq km, authors differ) and the lake is the terminal basin for a number of streams and rivers. Annual inflow is 6900 x 10⁶ m³ (Ghaheri et al., 1999). During spring runoff a freshwater plume covers large areas over the saline lake near river mouths. Prominent perennial streams include the Zarrineh River (230 km long) entering from the south and draining part of the northern Zagros with a range in discharge of 10-510 cu m per second with the Tata'u or Simineh River (145 km) as a major tributary, the saline Aji Chay or Talkheh (= bitter) River from the east draining the flanks of Kuhha-ye Sabalan at 4810 m (38°15'N, 47°49'E) and Kuh-e Sahand at 3710 m (37°44'N, 46°27'E), and the smaller streams from the west such as the Zowla (= "Zola") Chay (84 km), Nazlu Chay (85 km), Shahr (= "Shaher") Chay (70 km), Baranduz Chay (70 km) and Gadar (= "Qader") Chay (100 km) (Günther, 1899). Both the Zarrineh and the Talkheh exceed 200 km in length. The Talkheh River has a hardness of 820 mg/l according to Surber (1969), who also gives values of total alkalinity and calcium-magnesium hardness for a number of streams and lakes around Tabriz. The Talkheh floods extensively in the spring and forms large marshes. Most streams were relatively hard like the Talkheh although some were soft such as the Basmenj Chay draining Kuh-e Sahand at 70 mg/l.

Lake Kobi (= Ghopi) is a Ramsar Site lying at 36°57'N, 45°52'E and 1240 m altitude in this basin. It is south of Lake Orumiyeh and northeast of Mahabad. It comprises the fresh to brackish lake and associated but discontinuous marshes of about 1200 ha. The endorheic lake is shallow with a maximum depth of 1.5 m and a mud bottom. It is fed by precipitation and springs, and when full floods marshes to the north. It freezes over in winter. The lake is eutrophic and has reedbeds of Phragmites communis and abundant submerged vegetation. Livestock grazing and wildfowl hunting occur.

The Shur Gol and the "Yadegarlu" (= Yadergarlu) and "Dorgeh Sangi" endorheic lakes are at 37°00', 45°26-35'E south of Lake Orumiyeh and northwest of Mahabad at 1290 m are also a Ramsar Site comprising 2500 ha of lakes and associated marshes. They are fed by precipitation, springs and small streams. Shur Gol at 2000 ha is surrounded by the Hassanlu Marshes. Its water is brackish to saline. The eutrophic marshes flood in fall and winter and have abundant submerged vegetation. "Yadegarlu" is a shallow freshwater lake of 350 ha with abundant submerged vegetation and a surrounding of eutrophic sedge marshes. It may dry out in summer. It apparently suffered in the Iran-Iraq war (Jones, www.ramsar.org/lib_dir_2_3.htm, downloaded 4 April 2000) and may be deleted as a Ramsar Site. "Dorgeh Sangi" is 150 ha in extent and is a shallow freshwater and eutrophic lake. All three lakes may freeze over in winter. Reed cutting, grazing and waterfowl hunting occurs in this complex and some drainage of wetlands for agriculture may occur (Khan et al., 1992).

"Gerde Gheet" (Gordeh Git) and "Mamiyand" (= Meimand?) at 37°02'N, 45°40'E are freshwater marshes south of Lake Orumiyeh and north of Mahabad occupy 500 ha at 1300 m. The marshes are covered by Phragmites. Waterfowl hunting occurs here and some livestock grazing.

The "Ghara Gheshlaq" freshwater marshes at 37°10'N, 45°50'E occupy 400 ha at 1290 m south of Lake Orumiyeh and north of Mahabad. The water is about 1 m deep, eutrophic and freezes over in winter. Large parts of these marshes were drained by the "Mahabad Multipurpose Drainage and Irrigation Project" in the 1970s despite environmental concerns. Cornwallis (1976) notes both the draining of these marshes and the cessation of freshwater discharge from the Mahabad River. He also points out the likelihood of chemical contamination from agriculture, choking by vegetation and the probable use of herbicides. He recommends introduction of Ctenopharyngodon idella and Hypophthalmichthys molitrix. The marshes have been proposed as a Ramsar Site.

Lagoons in the Mahabad area dried in the year 2000 (www.irna.com/newshtm/eng/05142727.htm, IRNA, 26 July 2000).

Gori Gol or Lake Gory at 37°5'N, 46°42'E is a fresh to brackish lake near Tabriz occupying 120 ha at 1950 m. Depth is 2-3 m on average. It is a Ramsar Site (World Conservation Monitoring Centre, 1990; Scott, 1995). It is fed by precipitation, springs and small streams, with overflow through a small stream. The lake freezes over in winter. The submerged vegetation is abundant and there are extensive reedbeds of Phragmites communis, Juncus, Carex and Scirpus. It is under pressure from the population of the major city of Tabriz through sport fishing and wildfowl hunting as well as reed cutting and cattle grazing.

Qanats are found in this basin where surface water is saline. About 225 million cu m of water are produced annually by qanats and wells on the northern and eastern coast of the lake (Alamouti, 1966). Dams are found on the Zarrineh River and on the river which flows through Mahabad paralleling the Zarrineh. The Mahabad Dam has a fish catch of 130 tons (sic) annually and 300,000 fingerlings (species unspecified) were stocked to save the fish reserves from possible extinction (IRNA, 7 January 1999). The Mahabad reservoir has a leech fauna (Codonobdella trunata, Parcanthobdella livanowi, Baicalobdella torquata, Piscicola geometra) which may affect local fish farms and fish populations elsewhere if fish are transplanted (Abdi, 1999: www.mondialvet99.com, downloaded 31 May 2000). The Nowruzlu Dam on the Zarrineh is at 36°55'N, 46°10'E, occupying 1000 ha at 1260 m. It is water storage reservoir with heavy input from surrounding farming activities. The Alavian Dam near Maragheh is 80 m high, 935 m long and has a reservoir of 145 million cu m (http://netiran.com/news/IRNA/html/951214IRGG11.html). The Nahand Reservoir Dam northeast of Tabriz was inaugurated in 1995 with a capacity of 30 million cu m and a second dam, the Shahid Madani also near Tabriz, was under construction. Other dams include those at Ahar, Tabriz, Hashtrud, Hasanlu, Mianeh (= Onligh) and Heris which were scheduled to be completed in the period 1995-2000 (http://netiran.com/news/TehranTimes/95121601TTEC.html and www.irna.com/newshtm/eng/12003142.htm, IRNA, 2 July 2000). ? check basins for dams

The Hassanlou Reservoir Dam at Naqadeh was to open in 1998 with a height of 10 m, a crest of 5160 m (sic) and a capacity of 107 million cu m (http://netiran.com/news/IRNA/html/950915IRGG06.html).

A total of 6 reservoir dams and 10 dams for re-directing water flow will decrease water input to the lake by 1.04 billion cu m by 2014. The volume of surface water has fallen from 42 to 22 billion cu m since 1995. The lake salt has increased to more than 260g/l, up from about 185 g/l. The lake may well dry up by 2014 (IRNA, 10 September 2001).

Löffler (1993) details the eutrophication threat to this lake since a traffic embankment was built across the lake 35 km north of Orumiyeh in 1990. Untreated sewage from Orumiyeh will pollute the southern part of the lake.

Pollution occurs in various localities on a sporadic basis such as the Godar River in Naqadeh where a fish kill numbering in the thousands was reported (Tehran Times, 18 July 1999). Haji Hassani et al. (2004) found that levels of Ni, Pb and Cu in the Talkheh Rud were higher than acceptable limits for fish culture while Cr and Fe were lower. The river receives waste water from agricultural and industrial activities.

Water reservoirs behind the Mahabad, Miandoab and Shahid Kazemi dams were stocked with 3.6 million fish fry (species not specified) from the Pol-e Dasht Complex in 2000. This aquaculture site has the capacity to produce 4 million fry. West Azarbayjan produces over 600 tons of fish annually (Tehran Times, 2 January 2001).

Lake Orumiyeh is the largest natural habitat for brine shrimp in the world and, since 2000, is has been harvested, processed and used to feed sturgeon in hatcheries (www.worldfishingcompanies.com/html/us/world.report.html?id=1, downloaded 23 October 2001).

The lake was formed during the late Pliocene-Pleistocene and lies at 1275-1300 m and may well have had a Pleistocene connection to the Caspian Sea basin although this is in dispute (Scharlu, 1968; Schweizer, 1975). Pleistocene shorelines from 30 to 115 m above the present level have been confirmed, and the lake covered twice its present area, but this would not permit an external discharge. Berg (1940) reports benches at levels of about 1800 m, 1650-1550 m and 1500-1360 m, which may represent shorelines, and a level of about 1570 m would have had an outlet to the Aras River basin through the Kara-tepe Pass in the northwest and across the plain near Khvoy. Saadati (1977) suggests two connections with the Caspian Sea, an early one in the Pliocene to early Pleistocene resulting in endemic species and a later one in the late Pleistocene resulting in species which are the same as the Caspian or only subspecifically distinct. Stream capture may have allowed the entry of some species in recent times as evidenced by a Salmo trutta population.

Fish farming is extensive in West Azarbayjan. In the Iranian year ending 20 March 2002, 840 tonnes of coldwater fish were produced and 3000 t of warmwater fish (Tehran Times, 24 November 2002).

Günther (1899) details a method of catching fish used in the rivers of this basin. Flour and the pounded berries of Cocculus indicus are mixed with butter to form a stiff paste. Small pellets of the paste are thrown into slow flowing water and after 10-15 minutes, if the fish are feeding, they will begin to swim at the surface in small circles or lie helpless in the shallows and are then easily scooped up. Some fish can recover from the poison. There is no effect on humans if poisoned fish are eaten.

Berg (1940) considers that this basin falls within his assignment of the Iranian shore of the Caspian Sea. Species in common include Leuciscus (= Squalius) cephalus, Barbus lacerta, Gobio persus, Capoeta capoeta, Alburnoides bipunctatus, and Silurus glanis, and Acanthalburnus urmianus is related to A. microlepis. Groombridge (1992) notes that the ichthyofauna of this region is badly in need of re-examination.

Namak Lake

This basin is flanked by the Alborz Mountains to the north and the Zagros Mountains to the west. On the east is the vast expanse of the Kavir basin and on the south such ranges as the Kuh-e Karkas at 3899 m (33°27'N, 51°48'E). The basin encloses about 87,600 sq km.

A small sump near Arak (34°05'N, 49°41'E) is included as part of this basin as it is not separated by any major landform. A second salt lake is the Howz-e Soltan by the Tehran-Qom road and this lies in the same depression as the much larger Namak Lake south of Tehran. The lowest part of this basin is at 765 m and is covered by water in spring but this generally evaporates by the middle of summer.

The proximity of the capital, Tehran, to the rivers of this basin and its rapid growth in population and industry has led to many water diversionary schemes (Anonymous, 2003). A proposed dam northwest of Tehran would be the largest man-made lake in the country and the Middle East (sic) (Nouri et al., 2005). Much of this basin lies in Markazi or Central Province which has 42 dams of varying sizes. The Abbasabad Embankment Dam in Khomein, for example, is 36 m high, has a crest of 260 m and has a reservoir of 25,000 ha (IRNA, 3 February 1999).

The principal river in the west draining the Alborz south towards the Namak Lake is the Karaj River. Average temperatures of the Karaj River at the dam site before construction ranged from 2.5°C in January to 16.4°C in August (Nümann, 1966). Rieben (1954) and Hariri (1966) give details of surface and ground water in this river basin. The Amir Kabir Dam on the Karaj contains 205 million cu m of water and feeds through pipelines to Tehran. The reservoir has an area of 4 sq km at high water, 1.1 sq km at low water. Vladykov (1964) and Nümann (1966, 1969) give some details on the limnology of this reservoir, particularly temperature regimes. The Karaj has a discharge of 124 cu m per second in spring but this falls to 4.2 cu m per second in autumn. 55.6% of the annual discharge occurs during spring. There is no vegetation because of the steep rock sides and water fluctuations. Nümann (1966) recommended stocking the Karaj reservoir with Coregonus sp., Sander lucioperca, Acanthobrama terraesanctae (a Levantine species) and cichlids from Israel as environmental conditions and plankton levels were suitable. Nadim (1977) found the highest mercury levels in fish from the Karaj were 0.05 mg/kg. As the acceptable limit was 0.5 mg/kg, mercury contamination in fish was not considered a problem.

The Abhar River and its tributaries drain the land west of Tehran and south of Qazvin (36°16'N, 50°00'E). Its headwaters approach those of the Zanjan River, a Caspian Sea tributary. The course of the Abhar is about 350 km from its headwaters to the terminal sump. The lower part of this river is known as the Shur and is salty. Sewage and untreated factory wastes, as much as 40,000 cu m, flowed into the streams around the city of Qazvin although waste-water and sewage treatment plants are offsetting this problem (http://netiran.com/news/IRNA/html/941220IRGG05.html).

Other rivers draining the Alborz are much shorter. The Jajrud (Jaj, Jaji or Jaje River) to the east of Tehran is dammed at Latian (95 million cu m) for the Tehran water supply also. The Jajrud discharge is 60.5 cu m per second in spring and 1.5 cu m per second in autumn. Nümann (1966) reports fish kills in the thousands for Capoeta buhsei on turbid spring floods of this river. The Band Ali Khan River flows from the Khasrang Mountain (as does the the Jajrud which it receives) and its branches on the Varamin Plain are used for irrigation. Much of this river is polluted from wastes in the Jajrud and Tehran's sewage floodway (Rohani, 2004). The Lar River, a Caspian Sea tributary, was scheduled for diversion via a massive tunnel into the Jajrud (Marwick and Germond, 1975a; 1975b). This would affect flow in the Heraz River of the Caspian Sea basin and plans to offset this involved weirs and canal construction no doubt with the usual deleterious effects on fishes. These major projects are a far cry from the days in the twentieth century when Tehran depended solely on qanats for its water supply (Rieben, 1954).

The Namak Lake receives the Qareh Su (Gharechay), which flows north of Qom, and the Qom River from the Zagros Mountains. Discharge of both these rivers is about 312 cu m per second in flood falling to about 4 cu m per second in October (Oberlander, 1968b). The Qareh Su exceeds 400 km in length. The Qom River has captured headwater streams of Persian Gulf drainage. The Golpayegan River near Golpayegan has a storage reservoir, the Sadd-e Shah Esma`il. Borowicka (1958) gives some early figures on siltation and irrigation requirements. The Haroon Canal had diverted water for irrigation from the Golpayegan River for over 1000 years, and during the summer and fall all river water entered this canal. The Ghadir or Qadir Dam near Saveh has a volume of 290 million cu m of water. The 15th Khordad Dam is located 80 km south of Qom on the Qom-Delijan road (http://netiran.com/news/IranNews/html/95030718INPL.html). The Khandab Diversionary Dam is near Arak (http://netiran.com/news/IRNA/html/951217IRGG09.html).

Egglishaw (1980) gives some details on the water quality and environment of rivers and streams of this basin. Imandel et al. (1978) recorded ground water pollution by detergents in Tehran, where there was no method of sewage disposal other than discharge to wells and seepage pits. Södergren et al. (1978) reported on pollution with organochlorines in the Karaj and Latian reservoirs. Capoeta buhsei, Oncorhynchus mykiss, Alburnoides bipunctatus, Coregonus sp. had accumulated the DDT metabolite p,p^'-DDE, particularly in the Latian Reservoir. Direct removal of plants for fuel and laying bare the roots of such thorny plants as "giavan" for extracting gum tragacanth leading to plant loss has caused soil loss by erosion, gullying and affected recharge of groundwater. Poor farming practices on steep slopes has also led to the loss of topsoil such that runoff is too fast for infiltration of rain and snow (Rieben, 1954). These factors causing silting of reservoirs, added silt input to rivers and reduced groundwater recharge with consequent reduction in spring and qanat flows, all detrimental to fish habitats. Some areas of southern Tehran receive 300 kg/ha/yr of sulphate ions as acid rain which lowers river pH and has effects on the fish fauna (Salahi Kojoure, 1997). An effluent leak from a power station in the Vian area of Hamedan sent 40-50,000 litres of furnace oil into 1 km of river in the Qareh Su basin (Iran Network 1, Persian TV, 1730 GMT, 2 January 2000). Monavari and Mardani (2007) record the effects of sewage from fish culture ponds in this basin on water quality in the Jajrud, most factors being within acceptable limits except coliform bacteria.

Qanats are still a major feature of this basin. Alamouti (1966) records 260 qanats producing 99 million cu m per year on the Varamin Plain (35°20'N, 51°39'E), 220 qanats producing 161 million cu m per year on the Karaj Plain and 600 qanats producing 200 million cu m per year on the Qazvin Plain. However numerous pump wells have led to the drying of qanats and a complex irrigation system has reduced groundwater recharge (Beaumont, 1974). Alibekov (1994) gives a Russian account of qanats in Central Asia and also refers to those around Tehran in the Namak basin.

The Qazvin area has more than 20 aquarium fish farms producing over 2 million fish (www.tehrantimes.com, downloaded 28 July 2004). Waters in this area drain also to the Caspian Sea and there may be potential for escapes of exotics.

Berg (1940) refers this basin to his Tehran District of the Iranian Province. He notes that some drainages are close to those of the Caspian Sea basin and that the fauna may be of quite recent origin, rather than the Pliocene advocated by Derzhavin (1934) for Salmo trutta. Saadati (1977) considered that the fish fauna of this basin was not derived from movements through a large freshwater lake connecting all the tributaries. Some species came from the Caspian Sea basin and others from the Esfahan and Tigris River basins. The basin may also have served as a "filter-bridge" allowing such species as Capoeta aculeata, Capoeta capoeta and the progenitor of Capoeta fusca to reach the Dasht-e Kavir basin.

Sirjan

The Sirjan basin extends south-east of the Esfahan basin and parallels the Yazd basin. It is named for the town of Sirjan at 29°28'N, 55°42'E which lies at the edge of the largest salt flat in the basin. It is somewhat higher than the Esfahan basin which is at 1300 m, being 1448-1710 m. It is distinguished from the Esfahan basin by its lack of a significant river. There are four major sumps in this basin, strung out along its length at regular intervals, and the northern two are connected as are the southern two. The sumps are fed by intermittent streams. Qanats and minor springs are found in this basin which has not been extensively explored. The sump in the north near Abarqu (31°08'N, 53°17'E) receives streams from the west (Kuh-e Bul at 3661 m and 30°48'N, 52°45'E) and from the east (Khar Kuh at 3512 m and 31°39'N, 53°46'E, and Shir Kuh at 4074 m and 31°37'N, 54°04'E). The southern basins near Sirjan receive their streams from lower elevations.

Sistan

The Sistan (= Seistan) basin straddles the Iran-Afghanistan border and is a north-west to south-east oval in shape. It comprises a number of minor streams and qanats flowing from the west and the Birjand highlands, but these are rapidly absorbed or run for only a few days each year. Its most obvious feature is the vast hamun or swamp comprising open freshwater lakes, reed beds or neizar, and the rivers that feed the lakes. This is a major oasis of fresh water surrounded by hundreds of kilometres of arid plains. Huntington (1905a; 1905b), Annandale (1919a), Ahmadi and Wossughi (1988), Noorbakhsh (1993), Mansoori (1994), Ibrahimzadeh (1995), Scott (1995), Weier (2002) and CIRSPE (2006a) give descriptions of this basin. Note that Weier's (2002) statement (repeated in various newspaper reports and in UNEP (2003)) that there is nearly 140 species of fish in Sistan is an error by an order of magnitude! The native ichthyofauna comprises a mixture of endemic species, species related to or conspecific with high-altitude species from Central Asia and species from Baluchestan in the wider sense. There is little relationship to species from Iran to the west. Variations in water level and crowded conditions lead to disease and parasite outbreaks in the fishes (Mansoori, 1994).

The principal river is the Helmand (or Hirmand) which flows from the Paghman Mountains just west of Kabul to end in Sistan after a journey of 1400 km. Along with the Hari or Tedzhen, this is the only major river entering Iran. Snow and rain in the Hindu Kush mountains ultimately reaches Sistan at 427 m from heights of 5300 m. The Helmand is the most important river between the Tigris and the Indus and drains an area of 386,000 sq km of which 78,000 sq km or 20.2% lies in Iran (Gleick, 1993).

The Helmand produces 1700-2000 cu m per second in flood and 56 cu m per second in the dry season. The average annual flow is 78 cu m per second. The river varies between 200 and 900 m in width and between 2 and 5 m in depth. The annual water income to Iran is about 6 billion cu m but this varies markedly and was 14,740 million cu m in 1970-1971 and 1976-1977 and 600 cu m in 1985-1986 (Mansoori, 1994). UNEP (2003) gives the following flows in million cu m:-