The pikes, pickerels and muskellunge are found in fresh waters of the Northern Hemisphere. They are moderate to large-sized fishes, up to 1.4 m. There are only 5 species with 1 reported in Iran.

The family is characterised by a flattened, elongate, duck-billed snout; dorsal and anal fins far back on the body near the tail; no adipose fin; teeth on the tongue and on the basibranchial bones behind the tongue are small; jaws have large teeth; branchiostegal rays 10-20; nasal bones are present; the swimbladder is connected to the gut by a duct; intermuscular bones are forked or y-shaped; no fin spines; pelvic fins are abdominal; cycloid scales; the infraorbital sensory canal on the head has 8 or more pores; gill rakers are present as sharp denticles in patches; no pyloric caeca; the lateral line is complete; and the forked caudal fin has mostly 17 branched rays.

Pikes are predators on other fishes aided by the posterior dorsal and anal fins which facilitate rapid darts forward. They are important sport fishes, much sought after by anglers for their fighting ability, but are not very good eating because of the intermuscular bones.

Genus Esox
Linnaeus, 1758

The characters of this genus have been outlined above under the family.

Esox lucius
Linnaeus, 1758

Common names

ordak mahi (= duck fish from the snout shape), shok, shuk or shook (in Gilaki), shook chehkhab, chekab.

[durnabaligi in Azerbaijan; shchuka in Russian; pike; northern pike].

Systematics

Esox Lucius was originally described from Europe.

Key characters

The broad and flat snout and the dorsal and anal fins set far back on the body are distinctive.

Morphology

Dorsal fin principal rays 15-19, about 6-10 unbranched and 13-18 branched, principal anal rays 12-16, about 4-8 unbranched and 10-15 branched, pectoral rays 11-17 and pelvic rays 7-13. The number of branched rays may be size-related as in smaller fish more anterior rays in the dorsal and anal fins are not branched. Lateral line scales 105-148, pored scales 42-56, but difficult to count accurately. Each scale on mid-flank is a rounded rectangle. The anterior margin is indented where 1-2 radii terminate. The radii split the scale so that the segments overlap. Circuli are very fine and the focus is posterior. Gill rakers are broad and spinulose, embedded in the arch skin with the tips of the spinules protruding. There are 9-11 pores on the lower jaws (usually 5 on each jaw). Vertebrae 56-65. The chromosome number is 2n=50 (Klinkhardt et al., 1995). The gut is an elongate s-shape.

Meristic values for Iranian specimens are:- dorsal fin branched rays 14(7) or 15(9); anal fin branched rays 11(1), 12(8) or 13(7); pectoral fin branched rays 14(9), 15(5) or 16(1); pelvic fin branched rays 8(1), 9(7), 10(6), 12(1) or 13(1); pores on each lower jaw 5(22).

Sexual dimorphism

There is no obvious sexual dimorphism. Attempts have been made to sex pike by characters of the urogenital region, but these are hampered by seasonal variations. Abdurakhmanov (1962) reports on fish from Azerbaijan where head length is greater in males while predorsal distance and interorbital width are greater in females.

Colour

The overall colour is dark with light spots, although there is variation over the vast range of this species in the details. The back and upper flank are dark green, olive-green or brownish, fading to a whitish belly. The flank has 7-9 rows of greenish, yellow to whitish blotches along it. Scales have a golden tip. The head sides have wavy, golden or yellow blotches and lines and the eyes are bright yellow to golden. The dorsal, anal and caudal fins are green, yellow, orange or pale red, blotched and barred irregularly with black. The pectoral and pelvic fins are dusky to orange. Young have 8-12, wavy, white or yellow bars which become the bean-shaped blotches in adults as they gradually break up. There is a gold to green stripe along the middle of the back in some fish but others are completely dark green. There is a stripe below the eye. The peritoneum is silvery.

Size

Attains 1.75 m and about 48 kg despite legends of pike up to 5 m (Tsepkin, 1986).

Distribution

Across northern Eurasia and northern North America. Iranian populations are found in the Caspian Sea basin from the Anzali Mordab to Gorgan Bay and its tributaries and the Atrak River basin (Derzhavin, 1934; Berg, 1936; Armantrout, 1980; Holčík and Oláh, 1992; Nejatsanatee, 1994; Riazi, 1996; Abbasi et al., 1999; Kiabi et al., 1999; Jolodar and Abdoli, 2004).

This species has been introduced to Valasht Lake near Marzanabad, Avan River and Evan Lake northeast of Qazvin, the upper Karaj and middle Shur (Abhar stretch) rivers of the Namak lake basin, the Avan River near Alamut (in 1956), Ghorigol Lake near Tabriz, Marivan Lake in Kordestan, and the Haft Barm Lakes west of Shiraz (Anonymous, 1977; Petr, 1987; Niamir, 2001).

Zoogeography

This widely-distributed species reaches its southern range limit in Iran.

Habitat

Pike are solitary and are found in lakes and rivers where the water is still or flowing slowly as well as marshes and ponds. They are found only in the lower reaches of rivers along the Iranian shore and do not penetrate upstream (Berg, 1948-1949). O'Donovan (1882) reported that a small stream in the Atrak River drainage had many large pike lurking under bushes, stupefied by foul water, and that the Cossacks in his escort caught many of them by striking with the point of their sabres or simply whisked them out of the water by the tail. Large numbers of Rutilus frisii were seen here too and presumably the pike thrived on this food source. Riazi (1996) reports that this species is native (resident) to the Siah-Keshim Protected Region of the Anzali Mordab. They are found in the more brackish areas of the Caspian Sea, at least in Kizlyar Bay of the north Caspian, at salinities up to 4‰ under the influence of fresh water from the Volga River. Here they are found in thickets of soft and rigid vegetation, as solitary predators but also feeding beyond the vegetation limit in the sea. They aggregate only in spring for spawning and in autumn prior to wintering on the bottom (Stolyarov and Abusheva, 1997).

In fresh water, vegetation is heavy and the water warm but they usually retire to deeper, cooler water at the height of summer. Temperatures above about 30°C are usually fatal to pike. However pike are active in winter, as anglers can testify, and at this time can tolerate dissolved oxygen concentrations lower than 0.1 mg/l. pH range is 5.0-9.5 although they have been recorded as spawning at 4.2-4.4 but embryos are then malformed (Mann, 1996). Summer distribution is usually within 300 m of shore and less than 4 m deep. On windy days, pike retreat offshore in surface waters. Pike tolerate brackish water, up to about 7‰ for reproduction and 10‰ for feeding and growth. Reproduction requires living or dead vegetation (either aquatic or flooded terrestrial vegetation) in shallow, still waters protected from strong winds. Vegetation is also important for recruitment of young pike. Pike deposit their faeces at specific locations far from their usual feeding area as the faeces contain alarm pheromones recognised, and avoided by, prey species.

Age and growth

Life span is up to about 26 years but is less than half this in fast-growing southern populations. Some aquarium fish have lived 75 years. Maturity, like growth, varies with latitude and habitat, and also with quality of food. Higher temperatures may inhibit growth. Males mature at 1-6 years (30-46 cm) and females usually at 2-6 years, rarely at 1 year (31-63 cm). Females grow larger, faster and live longer than males. Growth is best at 19-21°C and is very efficient.

Nezami Balochy et al. (2005) examined this species in the Zibakenar-Kiashar Bojagh lagoon on the Caspian coast of Iran. The 122 fish were 17.7-74.0 cm long, average total length being 33 cm, and weight was 38-1100 g (average 307.3 g). The age groups were 0-9 years. Nezami et al. (2004; 2006) examined  this species in the Amirkelayeh Lagoon and found ages 1+ to 6+ years, average total length 44.8 cm (range 15.6-63.0 cm) and average weight 717.9 g (24-1700 g). Valipour (1998) investigated the pike in four areas of the Anzali Lagoon and found relatively fast growth with fish above 2 years of age mature with an average length of 32 cm.

In the Kizlyar Bay of the north Caspian Sea, males mostly mature at age 2+ with a body length of 36-40 cm while females are 3+ and 45-50 cm. Some males are mature in the first year of life at 26-30 cm and some females in the second year of life at 33-36 cm. Maximum age is 11 years in this population (Stolyarov and Abusheva, 1997). In Lake Aksehir, Turkey most males and females are mature at 2 years of age (Karabatak, 1988). Altindağ et al. (1999) give growth features for a population in a Kesikköprü Dam lake, Turkey where females reached age 5 and males age 4.

Food

Food is initially zooplankton and aquatic insects but fish begin to predominate at 5.0 cm after about 1 month's growth. Over 90% of the diet of adults is fish, but frogs, crayfish, mice, muskrats and ducklings are taken. Both sexes fast during spawning but females have rations 1.5-2.3 times as much as males in summer and winter. The daily ration was high from May to August with a June peak and very low in winter in North America.

Pike have a highly mobile eye which enables them to spot prey in almost any direction and have sighting grooves along the snout to facilitate their judgement of depth and distance. Food is seized after a rapid dart from concealment. Cylindrical fish like perch are preferred over more deep-bodied species as being easier to swallow. The prey capture process can be summarised as follows: eye movements towards prey, turning of body towards prey, stalking, darting, capture, rotating prey head first in mouth, and swallowing. Prey is sucked into the mouth which is opened just as the pike reaches its prey. Prey size is usually about one-third to one-half the length of the pike.

Valipour (1998) found feeding intensity and growth coefficient of this species in the Anzali Lagoon decreased with age. Fish in the 0+ age group fed mainly on zooplanktonic mysids while older fish took Carassius auratus, Hemiculter leucisculus, Rhodeus amarus and larvae of Alburnus chalcoides. Apparently, the pike is not restricting populations of commercial species in the lagoon but has an important role in controlling non-commercial exotics such as Carassius auratus and Hemiculter leucisculus. Abdoli (2000) lists Gambusia holbrooki, Carassius auratus, Hemiculter leucisculus, Liza saliens, Atherina boyeri and Alburnus charusini (= Alburnus alburnus) as food items for Iranian pike. The Zibakenar-Kiashar Bojagh lagoon fish had Odonata (14%) as the most frequent food, followed closely by Syngnathus abaster (13.8%) and Neogobius gorlap (13.4%). Other fish eaten included Gambusia holbrooki and pike. Nezami et al. (2004; 2006) examined  this species in the Amirkelayeh Lagoon and found the diet to be 24% Tinca tinca, 16% Proterorhinus marmoratus, with Esox lucius, plecopterans, frogs and water beetles at 8%, and Syngnathus abaster, Carassius auratus and Gammarus at 4%. Diet varied with season, and age and sex of the pike.

In the Kyzylagach or Imeni Kirova Bay of Azerbaijan Abramis brama, Cyprinus carpio, Rutilus rutilus, Rutilus frisii, Vimba vimba, Mugilidae, and Atherina boyeri are taken (Kuliev, 1989). Pike are cannibals when food is short. They compete with other piscivorous fishes, such as Sander lucioperca and Perca fluviatilis, for food. In the Kizlyar Bay of the north Caspian, the food of 2-month-old pike 3-4 cm long is mainly Rutilus rutilus fry, of pike 9-15 cm long this species plus fry of Cyprinus carpio and Scardinius erythrophthalmus, and of adults mainly Cyprinus carpio, Rutilus rutilus and Clupeonella cultriventris (during its spawning migration in April and May), Scardinius erythrophthalmus, Tinca tinca, Blicca bjoerkna, Alburnus alburnus, Cobitis sp., some gobies, frogs and crayfish. Sturgeon fry were once an important diet item but this declined with the decline in sturgeon numbers (Stolyarov and Abusheva, 1997).

Reproduction

The spring spawning migration in Dagestan begins at ice melt and spawning takes place from mid-March to the beginning of April when water temperatures reach 5-7°C. One batch of eggs is laid over a period of 10-15 days (Shikhshabekov, 1978). Spawning runs occur in the late evening and early night, several days before spawning occurs. Spawning takes place during the day, often in mid-afternoon, in shallow bays or flooded fields just after ice melt, generally in late March to May. Water temperatures on the spawning run are as low as 1.1°C. Spawning itself takes place at temperatures several degrees warmer than this, up to 17.2°C. Each female is accompanied by 1-2 males as she swims over vegetation in the shallow water. Both sexes roll to bring their genital regions close together, vibrate and release 5-60 eggs and the sperm. Tail sweeps scatter the eggs. This 3-10 second process is repeated many times each day. Eggs are amber, up to 3.4 mm in diameter after fertilisation, adhesive and each female can produce up to 595,000, although usually much less. In the Kizlyar Bay of the north Caspian Sea, the oldest females produce 365,000 eggs (Stolyarov and Abusheva, 1997). Eggs hatch 12-14 days later and the fry attach to vegetation by an adhesive head gland until the yolk sac is absorbed 6-10 days later.

The Kizlyar Bay population begins to spawn in late February or early March, sometimes under ice or immediately after ice melt at 4-6°C. Eggs are laid at depths of about 0.5 m and may dry out during water surges caused by northwestern winds although the increase in sea level has lessened this. Eggs adhere to vegetation but fall off after 2-3 days but do not die because of the low water temperatures and favourable oxygen conditions. Eggs hatch in 7-18 days depending on water temperature (Stolyarov and Abusheva, 1997).

Parasites and predators

Eslami et al. (1972) found helminths in 78.9% of 109 pike examined from Iran, a very high rate of infestation. The species encountered were Triaenophorus crassus, Raphidascaris acus and Contracaecum osculatum baicalensis. This latter parasite can infest man if fish is eaten smoked, salted or fried at temperatures below 50°C. Mokhayer (1976b) records the digenetic trematode Rhipidocotyle illense, the nematode larva Eustrongylides excisus, and the acanthocephalan Acanthocephalus lucii. Molnár and Jalali (1992) report the monogenean Tetraonchus monenteron from pike in Lake "Sama" in the Alborz Mountains. Ataee and Eslami (1999, www.mondialvet99.com, downloaded 31 May 2000) report Asymphylodora tinca from the gastro-intestinal tract of fish from the Anzali wetland. Naem et al. (2002) found the monogenean trematode Tetraonchus monenteron on the gills of this species from the western branch of the Safid River. Khara et al. (2006a) record the eye fluke Diplostomum spathaceum for this fish in the Amirkalayeh Wetland in Gilan. Sattari et al. (2002) and Sattari (2004) records the presence of the nematode, Eustrongylides excisus. This parasite can damage muscles in commercial species and render them unsuitable for sale. Sattari et al. (2005) surveyed this species in the Anzali, Amirkelayeh and Boojagh wetlands, recording Raphidascaris acus, Eustrongyloides excisus and Camallanus lacustris. Khara et al. (2006b) record the nematode Raphidascaris acus from this species in the Boojagh Wetland of the Caspian coast. Sattari et al. (2004; 2007) record the nematodes Camallanus lacustris,  Raphidascaris acus and Eustrongylides excisus, the digeneans Rhipidocotyle illense and Diplostomum spathaceum and the monogenean Tetraonchus monenteron in this species in the Anzali wetland of the Caspian shore. Miar et al. (2008) examined fish in Valasht Lake and the Chalus River, Mazandaran and found the metazoans Rhaphidoscaris acus and Tetraonchus menonteron.

Young pike are eaten by various other fishes including adult pike, birds and even large aquatic insects.

Economic importance

Nevraev (1929) reports a catch for the 1901-1902 to 1913-1914 period in the Anzali region was 1150 to 20,529 fish. Holčík and Oláh (1992) report a catch of 5836 kg in the Anzali Mordab in 1990, at 7.8% of the catch the fourth most important fish there, while annual reported catches from 1932-1964 varied from none to 98 tonnes. However it is not a favoured food fish in Iran (Vladykov, 1964).

There is some opportunity for sport fishing for this species in the Anzali Mordab and potentially in various lakes around the country where it has been introduced (Anonymous, 1977). Anglers catch this species in rivers along the Caspian shore such as in the Shazdeh River at Babol Sar (Noorbakhsh, 1993b). It is an important sport and commercial fish in other parts of its range. The catch in Turkey in 1981 was 796 tonnes and for the inland waters of the former U.S.S.R. in 1975 it was 16,101 tonnes. Stolyarov and Abusheva (1997) report a commercial stock of 2500 t with a recommended catch of 800-850 t in Kizlyar Bay in the north Caspian in the early 1990s.

The eggs or roe of this species are very poisonous as fresh extracts injected intravenously into rabbits have caused respiratory distress, convulsion and death within one hour (Halstead, 1967-1970).

Conservation

Raat (1988) gives details of conditions which should exist to facilitate pike reproduction and growth, including such factors as vegetation, water levels, eutrophication, pollution, prey availability, intra- and inter-specific interactions, fishery, stocking, concentration of dissolved solids, pH levels, and temperature regimes. Vladykov (1964) noted a fish kill in the Anzali Mordab on 11 June 1962 where water chestnut (Trappa natans) had caused an oxygen deficiency in the shallow water.

Gilan Fisheries Research Station has cultured pike in earthern ponds. Pike caught in autumn and winter were injected with gonadotropic hormone from carp (4-7 mg/kg). Eggs were stripped after 48-72 hours and incubated for 10 days at 8-11°C and 7-8 days at 10-15°C. Absorption of the larval yolk sac took approximately twice as long as the incubation period.

Ramin (1999) reports on a project involving artificial spawning and raising of fry in earthen ponds. Spawning temperatures were 8-15°C from 4 February to 20 March. Males and females were a minimum of 3 years old and a maximum of 5 and 6 years respectively and weighed 0.75-4.0 kg. Eggs composed 10-20% of body weight, incubation lasted 120 degree days and yolk sac absorption 160-180 degree days. The rate of fertilization was 45-85% and swelled eggs were 2.5-3.5 mm. Absolute fecundity was 22,400-112,000. Survival from larvae to fingerlings in chicken manure enriched ponds was 20-22% over 50 days with growth to 7.4 g and 8.5 cm on average.

Kiabi et al. (1999) consider this species to be conservation dependent in the south Caspian Sea basin according to IUCN criteria. Criteria include commercial fishing, sport fishing, medium numbers, habitat destruction, medium range (25-75% of water bodies), present in other water bodies in Iran, and present outside the Caspian Sea basin. Mostafavi (2007) lists it as conservation dependent in the Talar River, Mazandaran. Endangered in Turkey (Fricke et al., 2007).

Further work

The distribution and population numbers of of this species needs documentation in Iran.

Sources

Crossman and Casselman (1987) give a bibliography and Raat (1988) and Craig (1996) give synopses of biological data on this extensively studied species. General biology and characters are based on world-wide data. Sohrabi (1996b) gives an account of this species in Farsi.

Iranian material: CMNFI 1970-0510, 1, 250.3 mm standard length, Gilan, Golshan River (37°26'N, 49°40'E); CMNFI 1970-0535A, 1, 329.6 mm standard length, Gilan, Pir Bazar Roga (37°21'N, 49°33'E); CMNFI 1970-0542, 1, 39.0, mm standard length, Gilan, Old Safid River estuary (37°23'N, 50°11'E); CMNFI 1970-0543A, 1. 136.2 mm standard length, Gilan, Caspian Sea at Hasan Kiadeh (37°24'N, 49°58'E); CMNFI 1970-0553, 1, 136.7 mm standard length, Gilan, Sosar Roga (37°27'N, 49°30'E); CMNFI 1970-0579, 9, 71.9-111.2 mm standard length, Gilan, Old Safid River estuary (37°23'N, 50°11'E); CMNFI 1971-0343, 3, 63.8-74.7 mm standard length, Gilan, Langarud at Chamkhaleh (37°13'N, 50°16'E); CMNFI 1979-0685, 1, 149.2 mm standard length, Gilan, Safid River around Mohsenabad below Dehcha (no other locality data); CMNFI 1980-0123, 2, 126.3-209.3 mm standard length, Gilan, Safid River around Dehcha above Mohsenabad (no other locality data); CMNFI 1980-0138, 2, 148.2-164.3 mm standard length, Gilan, Safid River estuary (ca. 37°28'N, ca. 49°54'E); CMNFI 1993-0147, 1, 106.0 mm standard length, Iran (no other locality data).

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