1. INTRODUCTION

The freshwater fish fauna of the Islamic Republic of Iran is very rich as several drainages cross the borders of Iran and have either their head waters or lower reaches in this vast country. According to the lists by Coad (1979, 1980), completed by a description of a new species Aphanius vladykovi (Coad, 1988) and including Aristichthy nobilis (Richardson, 1844) which was introduced in the seventies, 27 families, 82 genera and 172 species of freshwater fish were recorded in Iran. The list of families, genera and species found in Iranian fresh waters belonging to the basin of the Caspian Sea amounts to 18, 52 and 96 respectively, and is the most numerous in comparison with other river basins of Iran. However, this list is still not complete as proved by the discovery of a further two species. These are described in this paper along with another two species not known from this territory.

2. RESULTS

Family: Anguillidae Regna, 1912
Genus: Anguilla Shaw, 1803
Species: Anguilla anguilla (Linnaeus, 1758) - eel

Seven specimens were caught near Bandar Anzali in December, 1989. Their total length varied from 750 to 990 mm and weight from 700 to 1 930 g. Some morphometric characters are summarized in Table 1.

Although Berg (1949) reported occasional records of this species from the Volga River delta, penetrating through canals connecting the Volga River with rivers entering the Baltic Sea, and also Coad (1980) quoted its occasional catches in the south Caspian Sea, there were no confirmed records of eel in Iranian waters. Iranian fishermen started to record eel in their beach seine catches some 15–20 years ago and in the past 15-10 years their annual catch varied from 40 to 60 specimens.

The main fishing ground for eel is the southern coast of the Caspian Sea between Bandar Anzali and the mouth of the Sefid River. According to fishermen's observations catch of eels seems to be increasing, but exact statistics are not known as this species is not used for food. However, their observations are in agreement with the situation on the northern and western coast of the Caspian Sea (Abdurakhmanov and Kuliev 1968, Kazancheev 1981) where the number of eels in the catch of the Soviet fishermen is also increasing. As stated by Kazancheev (1981) this is due to the regular introduction of elvers imported from France and the UK which are stocked in the Volga River. Abdurakhmanov and Kuliev (1968) recorded eels in the Kura River in Azerbaidzhan up to 50–60 km from its mouth. On the Iranian coast the eel is reported by fishermen also from the Anzali Lagoon¹. We are convinced that the eel enters also other rivers flowing from the northern slopes of the Elborz Mountains. Although the condition of these eels is better than those in the Baltic Sea drainage we are convinced that the introduction of this species into the Caspian Sea is of little use. One cannot expect the adaptation of the eel to the conditions of the Caspian Sea as Abdurakhmanov and Kuliev (1968) believed.

Family: Coregonidae Cope, 1871²
Genus: Stenodus Richardson, 1836
Species: Stenodus leucichthys (Güldenstadt 1771) - inconnu

¹ Anzali (Pahlavi) Bay or Anzali Liman (Enzeliiskii (Pekhleviiskii) zaliv or Enzeliiskii liman) in the Soviet literature. This water body is no longer a sea bay but a freshwater lagoon connected with sea by 5 channels (rogas)

² We are accepting the opinion of Reshetnikov (1980) that coregonids are well separated from salmons and graylings constituting thus the valid family Coregonidae.

Five specimens were caught 5–7 km east of Bandar Anzali in December 1984, 1988, 1989 and November 1990 respectively. Their fork length varied from 380 to 930 mm and weight from 560 to 7 600 g.

D 111-V 8–10, A 111-IV 11–13, 1.1. 99 105, gill rakers, 20–23, pyloric caeca (in two specimens, 487 and 675 mm in F1, the only available for this count) 139–145. Other measurements shown in Table 2.

The natural distribution of the inconnu in the Caspian Sea was said to be limited mostly to its northern, and rarely to its western part, south to 40oN lat. Its spawning migrations include the Volga River, rarely also the Ural and the Terek rivers (Berg 1948). Kazancheev (1981) mentioned only the first two rivers entering the northern part of the Caspian Sea as the spawning grounds for the inconnu, emphasizing explicitly that in the Kura and Terek rivers the inconnu has never been recorded. According to the latter author single specimens of the inconnu were caught along the Dagestan and Azerbaidzhan coasts of the Caspian Sea in early summer. However, inconnu has never been recorded in the southern part of the Caspian Sea. According to Mr. Bahram Ali Razavi, inconnu started to appear in the gill net catches of Iranian fishermen from the late sixties. All inconnu caught and amounting to several tons of individuals annually, come from the southern and southwestern coasts between the mouth of the Sefid and Astara rivers. The inconnu has never been recorded eastwards of the Sefid River. Fishermen report the catches of this species offshore, mostly above depths around 25 m from October until the end of December. Some specimens, however, come so close to the coast that they are caught by beach seines, as in the case of specimens caught on 4 November 1990. The weight of most specimens caught varies from 1–3 kg.

According to Mr. Rish Safi, the fish dealer in Bandar Anzali, 19 specimens of inconnu were delivered to the fish market during November and December 1990. The actual number caught is certainly higher than reported, as most fishermen consider this species to be ‘some kind of asp’ (Aspius aspius).

Specimens investigated by us display the age of 2+, 3, 5+ and 6+ respectively. Their growth rate data are very close to those given by Podlesnyi (1949) and Prokhorova (after Berg 1948):

It is likely that all specimens investigated by us belong to the nominate form leucichthys Güldenstädt, 1771 and not to the northern subspecies nelma Güldenstädt, 1773, which was introduced into the Volga River in 1965 but did not acclimatize there (Karpevich 1975). However, the differences between both forms are very slight, involving only some osteological characters (Shaposhnikova 1967, Reshetnikov 1980).

Migrations of spawners into the Volga River are now prevented by the Volgograd impoundment and other dams built upstream, and the stock of the inconnu in the Caspian Sea is supported by the massive stocking of fingerlings which amounted to 70 million in the period 1969–73 (Kazancheev 1981). Due to this and also due to establishing about 3.5 ha of artificial spawning grounds, the formerly low number of spawners, estimated by Letichevskii (1976, 1978) as 200–400 specimens in the seventies, rose to 30 000 in 1983 (Belyaeva et al., 1989). Consequently, also the catch of inconnu in the northern Caspian rose from 0.41 metric tons in 1959 to the present value of 20 metric tons.

Family: Salmonidae Regan, 1914
Genus: Oncorhynchus Suckley, 1861
Species: Oncorhynchus keta (Walbaum 1792) - chum salmon

Two specimens weighing 4–5 kg were caught in 1964 and 1972 on the southern and southwestern coast of the Caspian Sea between Bandar Anzali and the Astara River. None of them was preserved although one specimen was housed for a long time in the fish collection of the Fisheries Research Institute in Bandar Anzali.

The presence of the chum salmon on the Iranian coast of the Caspian Sea has been recorded already by Walczak (1972), but his information has not been published. It dealt with one mature specimen, but Walczak did not give any other data. The second specimen of the chum salmon was caught after 1972.

Both specimens came from numerous Soviet attempts to acclimatize the chum salmon in the Caspian Sea. This activity, which began in 1962 and continued until 1979 (Kazancheev 1981), was motivated by the continuous and steady decline of the endemic Caspian salmon (Salmo trutta caspius Kessler 1877). The first attempts seemed to be promising because spawning migrations and even the mass spawning of the chum salmon has been recorded since 1964 in the rivers entering the Dagestan coast (e.g. lower course of the Samur and Keiranchai rivers) (Magomedov 1970 a, b, Tamarin 1970, Karpevich 1975). Later on, however, spawning was only rarely observed and the chum salmon disappeared from the Caspian Sea. Vasilchenko and Goryunova (1980) recorded 11 adults in 1978 coming from 3.5 million juveniles released in 1975–76. In the sea only single specimens of chum salmon were caught in the northern Caspian, delta of the Volga River and the southern Caspian Sea (Kazancheev 1981). Their length varied from 470 to 720 mm in F1 and their weight from 1 250 to 4 800 g (Kazancheev 1981).

Together with chum salmon, the pink salmon (Oncorhynchus gorbuscha (Walbaum, 1792) and the coho salmon (O. kisutch (Walbaum, 1792) were introduced into the Caspian Sea (Karpevich 1968, 1975, Vasilchenko and Goryunova 1980), but these species did not acclimatize there either. Only a single specimen of the pink salmon was caught in 1964 (Karpevich 1975).

It has been suggested by Vasilchenko and Goryunova (1980) that the failure of introduction attempts in this case was the constant and strong wave action along the coast of Dagestan, where the juveniles are stocked, causing mass mortality. We suggest that the low salinity of the Caspian Sea, which is only around 10 ‰, i.e. two-thirds less than that in the Sea of Japan, has some influence on the low survival of the Far East salmons.

Family: Cyprinidae Berg, 1912
Genus: Hemiculter Bleeker, 1859
Species: Hemiculter leucisculus (Basilewski, 1855) - common sawbelly

Five specimens (3 females and 2 males) 134.5 to 149.1 mm in S1 were collected from a fisherman's gill net catch by Mr. D. Haghighi and Mr. M. Karimpour in the central part of the western region of the Anzali Lagoon in May, October and November 1990.

D 11–111 6–7, A 111 11–13, 1.1. 50 54, gill rakers 17–19, pharyngeal teeth uncinate, in three series: 2.4.5–5.4.2, 2.4.5–4.4.2, 2.4.4–5.4.2, 2.4.4–4.3.2. A sharp scaleless keel running from the anal opening to throat and ending behind the pectoral fin; second unbranched ray of the dorsal fin transformed into a sharp spine with flexible tip; there is a narrow dark band on dorsum running laterally from head to caudal fin; lateral line steeply descending from the beginning until almost the end of pectoral fin, then running parallel to the lower contour of the belly and then in the front of anal fin curving upward and running over the lower part of the caudal peduncle. Measurements and counts given in Table 3.

This species is highly variable and due to this it is known in literature under its junior synonym Hemiculter eigenmanni (Jordan and Metz, 1913). Although Nikolskii tried to prove that eigenmanni is a valid species, Yi and Wu (1964), Banarescu (1968) and also Vasileva and Kozlova (1988) repeatedly came to the conclusion that H. leucisculus and H. eigenmanni are conspecific and the latter is only a synonym of the former. Counts and measurements of our specimens agree well with data introduced by the above mentioned authors. An exception is dorsal fin count as we found only two unbranched rays in two specimens and only 6 branched rays in one.

H. leucisculus is an exotic fish for the Caspian Sea drainage and Iran as well. Its original distribution includes the rivers of China, Korea and Vietnam, and also the basin of the Amur River (Vasileva and Kozlova 1988). In the fifties and sixties the common sawbelly and other coarse fish were accidentally transferred with juveniles of the Chinese carp from China into Central Asia (Kazakhstan, Uzbekistan; Makeeva 1972, Borisova 1972). As the latter were imported into Iran from the USSR in 1967 it is almost certain that the consignment of Chinese carps contained also the common sawbelly. We suppose that this species is more widespread in Iran but it is not recognized as people consider it to be a native Caspian shemaya, Chalcalburnus chalcoides iranicus Svetovidov, 1945. Since September 1990, when the common sawbelly was recognized by the senior author of this paper, the total number and weight of this species in the Anzali Lagoon amounted to 92 and 5.25 kg respectively.

3. DISCUSSIONS AND CONCLUSIONS

Two of four species described in this paper, i.e. the eel and the inconnu, are native to the basin of the Caspian Sea and its drainage, although the penetration of the first species was enhanced and later on also supported by the artificial connections between the Baltic and Caspian seas and by stocking of elvers respectively. The other two species are exotic ones. The chum salmon was intentionally introduced but the common sawbelly was accidentally imported with consignments of Chinese carps. Apart from the latter the other three species reached the Iranian coast of the Caspian Sea naturally. The most probable route was along the western coast by means of the water current running parallel to this coast. The water circulation in the Caspian Sea is sub-divided into at least three closed rings moving counterclockwise but the main currents follow the north to south direction close to the shores (Fig. 1). We suppose that the appearance of the inconnu near the Iranian coast, as well as the increasing number of specimens caught during the past decade, is due to the rising water level and the decreasing salinity of the Caspian Sea (Gilitsyn 1987, Ivanov 1989, Balyaeva et al., 1989). Since 1977 when the Caspian Sea dropped to its lowest level since 1879 when the sea level measurements in the Caspian Sea were initiated, its constant and relatively rapid rise is observed. According to the measurements from the Bandar Anzali water gauge, the Caspian Sea level increased from -30.03 m in 1977 to -28.62 m in 1989, i.e. by 1.41 m within 12 years, and the present water level is even higher than the approximate average Caspian Sea level for 1879–1930 (-28.7 m). At the same time, salinity values (in northern Caspian) dropped from 10.24–10.73 ‰ in 1977 to 8.55–8.82 ‰ in 1983 (Belyaeva et al. 1989).

While the presence of the eel and the chum salmon is not important from an economical or environmental point of view, the role of the inconnu and the common sawbelly in the aquatic ecosystem remains to be identified. Inconnu is among the most valuable pan fishes of the Caspian Sea. It is presumed that their density will increase further, as the number of fingerlings to be stocked into the Volga River should reach 50 million annually in the near future (Belyaeva et al. 1989). Consequently, the catch of this species in the Iranian waters will certainly rise. It may be hypothesized that a local stock of the inconnu might be established. However, the question is whether the inconnu population in the Southern Caspian is a resident one or composed of fish dwelling temporary in this region. The inshore occurrence of inconnu during the autumn and winter months seems to indicate the resident population as in the Northern Caspian the bulk of the inconnu catch is taken just in this period of the year, when they perform the prespawning migrations from the sea (Berg, 1948, Kazancheev 1981, Belyaeva et al. 1989). However, to prove the presence of the resident population in the Southern Caspian one needs to know the stage of the inconnu gonad's ripeness. Natural spawning of the inconnu in Iran is undoubtedly out of the question, as the Sefid River, the only river which could be considered for the reproduction of this species, is both dammed and heavily silted. The inconnu stock in the Southern Caspian could be enhanced through artificial reproduction and stocking.

Concerning the common sawbelly the situation is rather ambiguous and needs special investigations. Borisova (1972) blamed this species for the partial displacement of the native species. The species is considered quite palatable and suitable for preparation of good quality salted or smoked fish products. Markovtsev (1980) suspected some negative impact of the common sawbelly upon the juveniles of the commercially important fish in the Hanka Lake (Amur River basin) where this species is native. This was confirmed by Borisova (1972) who indicated that in new environmental conditions its role is rather negative. According to our opinion the common sawbelly might be a serious competitor for food with the juveniles and also adults of some commerially important Iranian fish, both native and introduced. Its food consists of a wide variety of organisms including macrophytes and algae and the fish can easily switch fron one item to the other (Markovtsev 1980). It means that the common sawbelly is able to utilize all available food resources and at high densities it may considerably reduce the food resources available for the native fish. It could be a serious food competititon in the Anzali Lagoon where some types of food may be in short supply (Kimball and Kimball, 1974).

Acknowledgements

Mr. Irdzh Pir Rish Safid, a fish dealer in Bandar Anzali and Eng. N. Gorouhi, Head of the Experimental Hatchery of the Gilan Centre of the Fisheries Research and Training Organization in Bandar Anzali allowed us to take counts and measurements from Stenodus leucichthys and Anguilla anguilla specimens respectively. Dr. Brian W. Coad from the Canadian Museum of Nature in Ottawa, Canada, drew our attention to the unpublished paper of Walczak and some other information sources. We thank them all.

References

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Address of authors: Dr.Juraj Holčík, Institute of Zoology and Ecosozology of the Slovak Academy of Sciences, Department of Ichthyology, Drieňová 3, 826 24 Bratislava, Czech and Slovak Federative Republic, Mr. Bahram Ali Razavi, M.S., Fisheries Research Organization, Iranian Fisheries Company, P.O.Box 66, Bandar Anzali, Gilan Province, Islamic Republic of Iran

Table 1: Some morphometric data on Anguilla anguilla from Iran

+ head deformed

Table 2: Counts and measurements of Stenodus leucichthys from Iran

Table 3: Counts and measurements of Hemiculter leucisculus from Iran

Legend to text figure

Fig. 1: Schematic map showing the water circulation in the Caspian Sea (after Apollov et al. 1969) and some more important localities mentioned in the text. 1 - Bandar Anzali, 2 - Anzali Lagoon, 3 - Sefid River, 4 - Astara River, 5 - Kura River, 6 - Keiranchai River, 7 - Samur River, 8 - Terek River, 9 - Volga River, 10 - Ural River.