Species Accounts - Cyprinidae - Carassius

Revised:  19 June 2008

Pelz (1987) discusses the scientific name of the goldfish and its confusion with Carassius carassius. All diploid goldfish of western Europe are Carassius auratus auratus (from introductions, presumably including releases and escapes in Iran) and all triploid goldfish are C. auratus gibelio from eastern areas. Goldfish do not appear to be native to Iran but Iranian specimens are sometimes referred to Carassius auratus gibelio (Bloch, 1782) known as the Prussian carp, European goldfish or silver crucian carp. Berg (1948-1949) considers the familiar pet "goldfish" to be a domesticated form of the Prussian carp. However these fish probably have a number of origins - from aquarium stock and from China. Kottelat (1997) tentatively recognises Carassius gibelio (Bloch, 1782) as a species native to eastern Central Europe, and Kottelat and Freyhof (2007) map gibelio as the introduced species in the Caspian Sea basin of Iran. Vasil'eva and Vasil'ev (2000) state that fish named in the literature as Carassius auratus gibelio from Europe, Siberia and eastern Asia are triploids and are not a valid subspecies of C. auratus s.s. They consider C. gibelio to be a distinct species as long as it has a unique and ancient origin rather than arising de novo, and as long as the type specimens are triploids. Szczerbowski in Bănărescu and Paepke (2002) recognises C. a. auratus and C. a. gibelio.

Additionally C. auratus may be a tetraploid derivative of Carassius carassius. The native distribution of C. carassius is in Europe and western Asia, reaching northern drainages of the Caspian Sea in the southern limits of its distribution (Libosvárský, 1962). It differs from C. auratus in having a slightly convex margin to the dorsal fin (straight or slightly concave in C. auratus), caudal fin slightly emarginate (deeply emarginate), usually 6 branched anal rays (always 5), 23-33 gill rakers (37-53), 31-34 vertebrae, usually 32-33 (28-31, usually 29-30), 28-29 fin denticles posteriorly on the dorsal fin spine (10-11), peritoneum light (dark), black spot at the caudal fin base in young and some adults (absent), and a coppery gold body (silvery, pinkish gold, gold or red) (Szczerbowski in Bănărescu and Paepke, 2002). Berg (1948-1949) also cites the characters body rounded, back thick (body angular, back compressed) and scales weakly sculptured (rough), although his comparison is with C. a. gibelio.

Goldfish commonly hybridise with Cyprinus carpio to further confuse the identity of these fishes (L. Nico, http://nas.er.usgs.gov/fishes/accounts/cyprinid/ca_aurat.html, downloaded 24 May 2000). The identity of "goldfish" in Iran has not been thoroughly surveyed and, along with conflicting views on species and widespread introductions from many sources, make it simpler to refer to this taxon as C. auratus for now.

Al-Mukhtar and Al-Hassan (1999) describe a hybrid of this species and Barbus sharpeyi from Al-Hayei (= Al Ha'i), a seasonal lake between the Karkheh and Dez rivers in Khuzestan.

Key characters

The combination of spines in both the dorsal and anal fins and the absence of barbels is unique to this species. Szczerbowski in Bănărescu and Paepke (2002) distinguishes the subspecies auratus from gibelio by 21-36 lateral line scales (27-35 in gibelio) and a pink or gold colour (yellowish silver), not very diagnostic. Ilhan et al. (2005) give gill raker numbers of 34-40 for auratus, 42-56 for gibelio and 25-32 for C. carassius in Turkish waters (however note below that counts can increase with growth and see also under C. carassius for somewhat different counts and other distinguishing characters).

Morphology

Dorsal fin with 3-4 unbranched rays followed by 12-20 branched rays, anal fin with 2-4, usually 3, unbranched rays followed by 5-6, usually 5, branched rays, pectoral fin branched rays 11-18, and pelvic fin branched rays 6-9, usually 8. Dorsal and anal fin spine denticles coarse and few (about 10-15).

Lateral line scales 21-36. The anterior scale margin is wavy and there are very few anterior and posterior radii, as few as 3-4. The focus is slightly subcentral posterior. Circuli on the exposed part of the scale are more coarse and widely spaced than on the concealed part of the scale. Gill rakers long with serrated interior margins, reaching the fifth to eighth raker below when appressed with younger fish having longer rakers proportionately. Counts are size dependent in the range 34-54. Total vertebrae 25-34. Pharyngeal teeth 4-4, with very elongate, narrow, flattened and horizontal cusps arising from a much narrower stem. The gut is coiled with several loops. This species is variously reported as only diploid or as a tetraploid (2n=100-104); see above.

There are elongate specimens (morpha humilis, where fish density is high) and deep-bodied specimens (morpha vovki, where fish density is low) but these names have no taxonomic significance.

Meristic values for Iranian specimens are:- dorsal fin branched rays 16(4), 17(3), 18(3), 19(5) or 20(2); anal fin branched rays 5(17); pectoral fin branched rays 11(1), 14(1), 15(4), 16(10) or 17(1); pelvic fin branched rays 7(2) or 8(15); lateral line scales 28(6), 29(9) or 30(2); pharyngeal teeth 4-4(10); and total vertebrae 32(2).

Sexual dimorphism

Breeding males have small nuptial tubercles on the operculum, back and pectoral fin rays.

Colour

The golden or orange colour of artificially bred aquarium goldfish is distinctive. However populations in the wild, if they breed successfully, gradually revert to a wild-type of colour, without the appropriate diet supplement of aquarium fish and, as golden fish, are readily seen and eaten by birds and other fishes. Yanar and Tekelioğlu (1999) found that pigmentation increased with fish weight when specimens were fed the carotenoid zeaxanthin. Wild-type colour is an overall olive-green fading to a white belly. Flanks can be silvery to almost black. Fins are a dark olive-bronze, the membranes in particular being heavily pigmented. Young goldfish are usually green, brown or bronze to almost black and only after about 1 year do they take on the colour of adult auratus or gibelio. Peritoneum dusky to black.

Young fish at Ahvaz, Khuzestan, however, are a bright silvery overall (more so than Cyprinus carpio of similar size), the back is grey, the caudal fin is grey on the proximal half and hyaline distally, and the anal fin rays are white (and thus partly resemble gibelio).

Prussian carp (subspecies gibelio) is a dark steel colour with dark blue or greenish dorsally, silver-grey laterally and white ventrally, dorsal and caudal fins are dark grey and the paired fins and anal fin are light pinkish (Szczerbowski in Bănărescu and Paepke (2002).

Size

Attains 52.0 cm and about 5.0 kg, the subspecies gibelio being smaller, up to 45.0 cm and 1.24 kg.

Distribution

The native distribution is in northern Asia and China, reaching northern drainages of the Caspian Sea in the western limits of its distribution (Libosvárský, 1962; Plez, 1987). The goldfish has been widely introduced to garden ponds and released from aquaria in temperate to warm waters world-wide. In Iran it has been introduced throughout the Caspian Sea basin where it is reported from the Atrak, Gorgan, Gharasu, Tajan, Babol, Haraz, Sardab, Aras (including the middle Aras and lower reaches of its tributary the Qareh Chai), Tonekabon, Pol-e Rud, and Safid rivers, the Anzali Mordab where it is now the most abundant fish, and Gorgan Bay (Holčík and Oláh, 1992; Shamsi et al., 1997; Roshan Tabari, 1997; Abbasi et al., 1999; Kiabi et al., 1999; Abdoli, 2000; Gasmi and Mirzaei, 2004); the lower Talkheh and lower Zarrineh rivers in the Orumiyeh basin (Abdoli, 2000); the lower Shur, lower Qareh Chai and the Latian Reservoir in the Namak Lake basin (Armantrout, 1980; Hosseini, 1987; Abdoli, 2000); the Hamun Kushk and the Sistan Dam as well as throughout the hamuns in the Sistan basin (Ahmadi and Wossughi, 1988; Mansoori, 1994; J. Holčík, in litt., 1996; field work in the 1970s); Yazd and Lut basins generally (Abdoli, 2000); lower Kashaf River in the Tedzhen basin (Abdoli, 2000); throughout Khuzestan where now common (N. Najafpour and M. Al-Mukhtar, pers. comm., 1995; field work 2000, absent in 1970s); middle and lower Hilleh and lower Mand rivers in the Gulf basin; middle Halil and middle to lower Bampur River (Abdoli, 2000); Dalaki and Shapour rivers (Pazira et al., 2005), and found in garden and park ponds throughout Iran. Some introductions are probably discarded aquarium fish as goldfish are sold as pets and for the Now Ruz (= New Year) festivities. They may also have been introduced accidentally with the commercially important Chinese carps.

This species is also recorded from the Karakum Canal and Kopetdag Reservoir in Turkmenistan (Shakirova and Sukhanova, 1994; Sal'nikov, 1995) and may eventually reach Iranian waters from this source in the Tedzhen (= Hari) River basin.

The Prussian carp (subspecies gibelio) is less widely distributed and its presence and distribution in Iran are not known.

Zoogeography

This species has been introduced to Iran by man. Some are undoubtedly aquaculture pond escapees or aquarium releases. Goldfish are kept in aquaria as part of the Now Ruz (New Year) celebrations in March each year. Tehran television (and the Green Front of Iran, see below) urged people to release them into local waters rather than killing them after the New Year (J. Valiallahi, pers. comm., 2000).

Habitat

Goldfish are hardy and can live in winterkill water bodies with much aquatic vegetation, low oxygen, and high pollution (Gudkov, 1985). They can also survive several hours out of water (Pelz, 1987) and may bury themselves in mud, albeit temporarily when scared (Szczerbowski in Bănărescu and Paepke, 2002). Goldfish appear to favour ponds or pools in streams with aquatic vegetation but are often introduced into small bodies of water as ornamental fish. They are tolerant of turbidity, e.g. clay at 225,000 mg/l, pH from 4.5 to 10.5, very high temperatures (upper lethal limit 41.4°C), and high salinity (17‰). This species was killed under experimental conditions, when gradually acclimated to increasing salinity at 28,200 μmho and, by sudden exposure, at 19,200 μmho (Jassim, 1988). This is a greater tolerance than that shown by Cyprinus carpio, another exotic introduced to Iran. However, Carassius auratus appeared in the Basrah fish market when an increase in the Tigris River discharge reduced the salinity of the Shatt al Arab (N. A. Hussain, in litt., 1994).

In Iran it is one of two most abundant species in Caspian wetland areas along with Gambusia holbrooki (Iranian Fisheries Research and Training Organization Newsletter, 19:4, 1998).

Age and growth

Maturity is attained at 3-4 years in the Volga Delta for goldfish. Life span is 13 years with most growth in the first 2-4 years to a size of 15-20 cm (Gudkov, 1985; Kizina, 1986). Life span in captivity in China may exceed 50 years. Population numbers in confined areas are limited by a chemical released by the goldfish which represses more spawning. Prussian carp live up to 11 years.

In the Anzali Mordab, Holčík and Oláh (1992) found only 6 age groups (as did Bagirova et al. (1990) in reservoirs of Azerbaijan while Pipoyan and Rukhkyan (1998) found 9 age groups in Armenia) with the largest fish 32 cm standard length owing to intense fishing pressure. Growth in mm increments was successively 93, 47, 50, 42, 28, and 37. The population is entirely female (see below). Individual life span is greater in Armenia where males are scarce or absent than in bisexual populations (Pipoyan and Rukhkyan, 1998). Sayad Borani et al. (2001) studied this species (as C. auratus gibelio) in the Anzali Mordab at four localities and found a mean fork length of 19.5 cm (range 2.5-31.5 cm) and a mean weight of 196.8 g. The mean age was 2.6 years. The mean length, weight and age were higher in the Sia-Keshim area of the lagoon. The exploitation rate was 0.47, L_∞ was 36.0 cm and K was 0.23 per year. Esmaeili and Ebrahimi (2006) give a significant length-weight relationship based on 41 Iranian fish measuring 5.65-8.17 cm standard length. The a-value was 0.0419 and the b-value 2.911 (a b-value < 3 indicating a fish that becomes less rotund as length increases and a b-value >3 indicating a fish that becomes more rotund as length increases).

Fish in Buldan Dam Lake, Gediz River basin, Turkey referred to C. gibelio had a maximum age of 6 years and attained 25.5 cm and 269.1 g (Sarı et al., 2008). von Bertalanffy growth parameters were L_∞ = 31.66 cm, W_∞ = 635.91 g, k = 0.146 year^-1 and t₀ = -2.166 year. Ratios of total, natural and fishing mortality were calculated as 0.632 year^-1, 0.456 year^-1 and 0.176 year^-1.

Food

Food is predominately zooplankton but also includes aquatic insects, crustaceans, molluscs, worms, detritus, filamentous algae, macrophytes and young fish, switching from one kind of food to another as circumstances warrant. Goldfish have a palatal organ on the roof of the mouth used to taste and touch food and their dense gill rakers aids in feeding on smaller food items. In the recovering Hawr al Hammar, Iraq, diet is 46.1% algae and 25.5% diatoms, with amounts of plants, crustaceans, insects, snails and fish being less than 10% each, in the Hawr al Hawizah 36.3% algae, 21.3% diatoms and 17.5% copepods, with amounts of plants, cladocerans, ostracods and insects being less than 10% each, in the Al Kaba'ish (= Chabaish) Marsh 45.5% algae, 25.2% diatoms, with plants, various crustaceans, insects and snails at less than 10% each (Hussain et al., 2006).

Reproduction

The fish in the Anzali Mordab are all female, reproducing through gynogenesis. Sayad Borani et al. (2001) found fish in Anzali Mordab to have a sex ratio of 99.3 females:0.7 males. Egg development is stimulated by sperm probably from Cyprinus carpio, Tinca tinca, Blicca bjoerkna or Scardinius erythrophthalmus. Here fish may mature at 1 year of age, and coupled with polycyclic ripening of eggs and intermittent spawning, this has led to the dominance of this species in the fresh waters of the lagoon (Holčík and Oláh, 1992). In Armenia, maturity appears to be linked with average annual temperature - at 12.0-13.1°C it occurs at the end of the first year of life while at 8.4-9.0°C it occurs at the end of third and fourth years (Pipoyan and Rukhkyan, 1998). Turkish populations in Topçam Dam Lake, Aydın (Şaşı, 2008) and Buldan Dam Lake, Gediz River basin (Sarı et al., 2008) referred to C. gibelio were 98.84% and 99.44% female. Spawning in the former locality was from March to August, suggesting multiple spawnings with mean fecundity ranging from 37,823 in August to 85,159 in March. Egg diameter reached 1.099 mm in June.

Spawning begins in late April to mid-May in the Volga Delta and occurs in May-June in the Anzali Mordab (Sayad Borani et al., 2001). Eggs are laid in 2-5 batches over a spawning period extending into July. Up to 10 batches are laid elsewhere at 8-10 day intervals with up to 4000 greenish-yellow eggs in each batch. Fecundity reaches 253,200 eggs (elsewhere to 685,700 with absolute fecundity reaching 860,000 eggs). The largest eggs are 1.6 mm in diameter (Gudkov, 1985; Kizina, 1986; Szczerbowski in Bănărescu and Paepke, 2002). Each female is accompanied by 2 or more males and chases are reported with splashing and shooting through the water near the surface. The eggs are adhesive and attach to water plants and hatch in 5-8 days.

Parasites and predators

Mokhayer (1976b) records infectious dropsy and swimbladder inflammation in Iranian goldfish. Saprolegniosis has been reported from goldfish in Iran (Rahbari and Razavilar, 1982). Growths of the fungus Saprolegnia parasitica resembled tufts of cotton wool. Mokhayer (1989) reports metacercariae of the eye fluke, Diplostomum spathaceum from this species in Iran, which can cause complete blindness and death in commercially important species. Jalali and Molnár (1990a) record the monogeneans Dactylogyrus baueri, D. extensus, D. formosus and D. vastator from this species in the Safid Rud. Jalali and Molnár (1990b) report a variety of monogeneans from this species variously in fish farms throughout Iran, namely Dactylogyrus baueri, D. dulkeiti, D. formosus, D. vastator and D. vastator forma minor. Molnár and Jalali (1992) record the monogenean Dactylogyrus intermedius from this species in a petfish farm near Tehran. Gussev et al. (1993a) describe a new species of monogenean from goldfish on a fish farm near Tehran, Dactylogyrus intermedioides. Shamsi et al. (1997) report Clinostomum complanatum, a parasite causing laryngo-pharyngitis in humans, from this species. The helminth Anisakis sp. is recorded from the guts of this species in the Anzali wetland (Ataee and Eslami, 1999; www.mondialvet99.com, downloaded 31 May 2000). Mousavi (2003) records the monogeneans Gyrodactylus sp., G. kabayashi, D. extensus, D. baueri, Trichodina sp., the ciliates Ichthyophthirius multifilis and Ichthyoboda sp. and the copepods Lernaea cyprinacea and Argulus foliaceus from this species in ornamental fish in Iran. Aquarium specimens are often released in the wild at New Year (Now Ruz). Naem et al. (2002) found the following parasites on the gills of this species from the western branch of the Safid River, namely the protozoans Ichthyophthirius multifilis and a Trichodina species, monogenean trematodes Dactylogyrus anchoratum, and Gyrodactylus sp.. Jalali et al. (2002) and Jalali and Barzegar (2006) record Diplostomum spathaceum from this species in Lake Zarivar. Naem (2002) records the monogenean Dactylogyrus anchoratus from fish in Safid River. Mehdipoor et al. (2004) record the monogenean Dactylogyrus baueri in this fish in the Zayandeh River. Masoumian et al. (2005) recorded the protozoan parasite Ichthyophthirius multifilis from this species in the Aras Dam in West Azarbayjan (species identified as C. carassius, presumably goldfish). Jalali et al. (2005) summarise the occurrence of Gyrodactylus species in Iran and record G. kobayashii and G. sp. in fish from 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. (2005) surveyed this species (as C. carassius) in the Anzali wetland, recording Raphidascaris acus (and larvae) Eustrongyloides excisus and Camallanus lacustris. Pazooki et al. (2007) recorded various parasites from localities in West Azarbayjan Province, and found Eustrongylides excisus. Sattari et al. (2007) record the nematode Raphidascaris acus, the digenean Diplostomum spathaceum and the monogeneans Dactylogyrus extensus,and Gyrodactylus sp. in this species in the Anzali wetland of the Caspian shore.

Economic importance

This species is raised on Tehran fish farms for the pet trade (Molnár and Jalali, 1992). In the Anzali Mordab, 62% of the total catch is goldfish, an accidental introduction (Petr, 1987). The catch in the mordab in 1990 was 46,472 kg (Holčík and Oláh, 1992). As the salinity of this lagoon increases, the density of goldfish will decrease. Valeipour and Haghighy (2000) record the catch for 1992-1996 at 40% of the species taken. Safaei (2005) gives a goldfish catch figure of 45% of the 313 ton fishery there in 1992. The presence of goldfish in the Anzali Mordab led to a decline in the native fishery there.

This species is caught by anglers at Ahvaz in Khuzestan using bread or potato as bait.

It is known to control mosquito larvae in Bengal (Chandra et al., 2008).

The peculiar type of reproduction is very successful and affects the catches of other cyprinid species, being equivalent to a predatory effect (Holčík and Oláh, 1992).

There is some evidence that this fish disturbs the habitat of native species, muddying waters, and it may compete for food and space. Goldfish have destroyed some amphibian populations in other parts of the world by consuming frog eggs (Coad and Abdoli, 1993b). The Green Front of Iran recommended the release into pools of mosques, parks or natural lakes of the estimated 20 million goldfish kept in aquaria for the Iranian New Year celebrations in March each year. This would have a deleterious effect on habitats not yet colonised by this exotic species. A news report in 2005 cites the death of 5 million fish in transit from the store to the Iranian home at New Year, indicating perhaps that the numbers that do make it are much higher (www.politicalgateway.com, downloaded 5 August 2005). Newspaper articles suggested that goldfish should only be released into "pools" rather than rivers because of all the attendant dangers of this exotic. They are known to prevent reproduction of native species in Sistan (Iran Daily, 17 March 2005, p. 5).

This species is used in Iran as an experimental organism, e.g. in studying the effects of anionic detergents (shampoos, a common water pollutant) on blood parameters, on hepatic and renal pathology and serum biochemical parameters (Shahsavani et al., 2005; Shahsavani et al., 2006; Shahsavani and Movassaghi, 2006); the use of phenytoin sodium on skin wounds (5mg/l showed best healing improvement)(Shahsavani et al., 2002); the effects of cortisol on testicular apoptosis (Bahmani et al., 2007).

Robins et al. (1991) list this species as important to North Americans. Importance is based on its use in textbooks, in aquaria and in aquaculture, as bait, as an experimental species and because it has been introduced outside its natural range. There are numerous, commercial aquarium forms with particular morphologies and colours that are assigned common names, e.g. common, veiltail, comet, fans, calicoe, black-moor, telescope-veiltail, lionhead, egg-fish, shubunkin.

Conservation

This species is a successful exotic, in no need of conservation.

Further work

The Carassius species in Iran is generally regarded as C. auratus, the goldfish of aquaria, as it is used extensively in Now Ruz (New Year) celebrations and often released into natural waters. This needs confirmation for all major populations.

Sources

Iranian material: CMNFI 1979-0230, 41, 14.7-38.6 mm standard length, Sistan, Hamun-e Puzak (ca. 31º15'N, ca. 61º42'E); CMNFI 1991-0162, 1, 40.5 mm standard length, Mazandaran, Bagher Tangeh (36º42'N, 52º43'E); CMNFI 1993-0136, 64.0 mm standard length, uncatalogued material, 1, 93.5 mm standard length, Gilan, near Hendeh Khaleh (ca. 37º23'N, ca. 49º28'E); 1, 52.8 mm standard length, Gilan, near Hendeh Khaleh (ca. 37º23'N, ca. 49º28'E); 4, 16.4-50.3 mm standard length, Gilan, near Khoshk Bijar (ca. 37º22'N, ca. 49º47'E).

Carassius carassius
(Linnaeus, 1758)

The crucian carp has been reported as introduced to Iran in the Karun River basin as aquarium releases by Armantrout (1980) without further details and there are other reports such as in the Gorgan River (Y. Keivany, in litt., 1992) and Mahabad Dam (Abdi, 1999; www.mondialvet99.com, downloaded 31 May 2000) but these may be confusion with Carassius auratus. Specimens are needed to confirm the presence of this species in Iran. The native distribution is in Europe and western Asia, reaching northern drainages of the Caspian Sea in the southern limits of its distribution (Libosvárský, 1962). It differs from C. auratus in having a slightly convex margin to the dorsal fin (straight or slightly concave in C. auratus), caudal fin slightly emarginate (deeply emarginate), usually 6 branched anal rays (always 5), 23-33 gill rakers (37-53), 31-34 vertebrae, usually 32-33 (28-31, usually 29-30), 28-29 fin denticles posteriorly on the dorsal fin spine (10-11), peritoneum light (dark), black spot at the caudal fin base in young and some adults (absent), and a coppery gold body (silvery, pinkish gold, gold or red) (Szczerbowski in Bănărescu and Paepke, 2002). Berg (1948-1949) also cites the characters body rounded, back thick (body angular, back compressed) and scales weakly sculptured (rough), although his comparison is with C. a. gibelio.

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© Brian W. Coad (www.briancoad.com)