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Gilan and Mazandaran Provinces on the Caspian Sea are at present the most important provinces of Iran for inland fisheries production. This is largely because of the high rainfall resulting in the presence of a considerable number of permanent freshwater bodies. There are numerous reservoirs and rivers, several lagoons and lakes. Sturgeon and semi-migratory fish enter rivers and lagoons connected with the Caspian Sea, for spawning and feeding. The presence of marsh-type aquatic vegetation in some lagoons and in the Gorgan River discharge area is of considerable importance for fish. At least one lagoon (Anzali) has freshwater fish. Gilan Province has about 10 000 ha of inland waters, of which more than 90% are estimated to be available for the inland fishery. Mazandaran has some 13 000 ha, of which 40% are with permanent water, the rest drying out during the summer.

4.1 Sturgeon

The last thorough review of sturgeon fishery of Iran was prepared by Vladykov (FAO, 1964), who included data up to 1962. These data record the decline in sturgeon catches during the first 60 years of this century. In the USSR artificial propagation of sturgeon for large-scale stocking of fingerlings started in 1955 (Bukhanevich et al., 1986). In Iran, the Sad-e-Sangar (Dr.Beheshti) fish farm for sturgeon fingerling production is situated 27 km from Rasht in Gilan Province. It produces up to 3 million 2–3 g sturgeon fingerlings per year for release. Sad-e-Sangar has a hatchery/nursery system for four species of Caspian sturgeon: chalbash (russkii osetr, Acipenser güldenstädti), karaburun (persidskii osetr, A. persicus), sheap (ship, A. nudiventris), uzun burun (sevryuga, A. stellatus). In Iran, the first three species are often grouped under the name tass mahi. The hatchery does not produce beluga (Huso huso). The original sole function of producing sturgeon has been broadened lately to produce also fry and fingerlings of mahi sefid (kutum, Rutilus frisii kutum) and common and Chinese (especially silver) carps.

The hatchery/farm, which employs about 150 people, including 60–70 specialists, has been producing sturgeon for stocking since 1971. The farm extends over an area of 120 ha, of which 72 ha is covered by fish ponds for sturgeon fingerling production. These ponds are also used alternatively for other fish produced on this farm. The mature fish captured in rivers are transferred into basins on the farm, where their eggs and milt are removed, eggs fertilized, incubated and larvae hatched. The fish larvae are transferred into circular concrete basins from where, after 15–20 days, when they reach 60–120 mg, they are moved into nursery ponds. A detailed description of the propagation of sturgeon is given by Milshtein (1972).

In 1986 the production of sturgeon larvae was about 11 million, and in 1987 14–15 million were produced from (females only): A. oüldentädti (48). A. persicus (26).

A. stellatus (54), and A. nudiventris (1). Iran is most interested in A. persicus as it gives a better quality caviar than other species. The highest number of larvae produced in this hatchery came from A. persicus. The young are fed on Daphnia, and later on oligochaetes, the latter being produced in a special air-conditioned building. Sturgeon fingerlings are kept in ponds for several months until they reach 10 to 15 cm length, after which they are trucked to a release site on the Sefid-Rud (river), about 20 Km upstream from the Caspian coast: this is to imprint the migratory instinct of sturgeon for the river, into which they may return in 10–15 years to breed. The number of sturgeon fingerlings released in 1985 was 1.13 million, in 1986, 2.28 million.

Woynarovich (1985) considered the technology applied in this hatchery as satisfactory, and gave the survival rate for eggs of 2 months age as 30–35%. Mortality rates given during the present visit were 20–25% for larvae in circular basins (as compared to 30–40% by Woynarovich), and 40% in the fingerling stage (30–40% according to Woynarovich).

Control against Apus, which is widespread and numerous and competes for food with sturgeon fingerlings, is done by using the pesticide Dipterex during the dry phase of the pond. However, Apus is still a problem as observed during the present visit, when both fingerling sturgeon and Apus were drained in large quantities from fingerling ponds into a collector canal for the sturgeon transfer into rivers.

Ivanov (FAO, 1964) summarized catches of three different groups of sturgeon in Iranian waters in five-year intervals, from 1930/31 to 1961/62 (Table 2). Summary information on total sturgeon landings are available in FAO Yearbooks of Fishery Statistics - Catches and Landings - for the period 1964–1985. There has been a slight increase in sturgeon landings in Iran during the last 6 years, for which more accurate data are available, after a long period of estimates. From the FAO statistics the following mean landings are calculated: 1964–1970 = 2300 t: 1971–1975 = 1800 t: 1976–1980 = 1500 t: 1980–1985 = 1774 t. During 1964–1972 the catches regularly exceeded 2000 t/year, with a range from 2100 to 2500 t: afterwards, they ranged between 1300 and 1774 t, but much of these data are repeats of the 1500 t value. Detailed statistical evaluation of data stored at the Bandar Anzali Research Institute is needed to assess changes in species composition, and to understand the impact of regular stocking of sturgeon fingerlings on catch. Data for sturgeon catches from the USSR Caspian Sea basin are presented in Table 3 (from Nikinorov 1986).

The increase in landings during the last 15 years has been attributed largely to the regular and increasing rate of stocking.

In the Soviet Union there are at present 13 fish farms on the Caspian Sea, producing 90 million sturgeon fingerlings annually. Three more fish farms are under construction, and by 1990, the fingerling production for stocking purposes is to reach 125 million.

The importance for fish stocks and fisheries of high water river discharges into the Caspian Sea has been recognized. Belyaeva amd Ivanov (1986) analysed the complex of factors determining favourable conditions for an optimal Caspian Sea fish stock development and reviewed measures which have been taken to improve fish stocks negatively affected by numerous new dam structures and water uptake from the inflowing rivers.

The first requirement for optimizing fish stocks in the Caspian Sea is not to allow the sea level to decline lower than -28.5 m below the world ocean level. The pattern of salinity distribution in the Caspian Sea and of water currents mixing riverine and sea water then change, resulting in changes in water productivity. A decrease by 1 m in sea level results in 60% reduction in fish food supply, and this lower sea level also places a barrier to the migration to better feeding grounds, resulting in another 20% loss of food supply. Thus, only about 20% of food is still available.

It has been suggested that to optimize the conditions for sturgeon and for other fish (semi-migratory and non-migratory), the sea level should be maintained at -28.5 m or above. For this purpose, the total discharges should be not less than 280 km3/year, with the following components: Volga - 235 km3, Ural - 9–10 km3; Terek - 6 km3; Kura - 9 km3. The discharges should be adapted to fish biological requirements: for example, on the Volga, during the floods, 120 km3 should be released. Belyaeva and Ivanov (1986) put forward a number of other constructive recommendations, which, if implemented, should result in at least doubling the present fish catch from the Caspian basin.

It is in the interest of both the USSR and Iran to maintain a favourable water level in the Caspian Sea for optimal natural reproduction and feeding of fish, and to enhance regularly the fish stocks through stocking. Long-term forecasts of fish production will remain difficult, as the climatic factor will always highly dominate over other factors, such as water demand by a variety of users. Regular bilateral meetings of an advisory/cooperative character should be initiated between Iran and the USSR on a diversity of factors related to the Caspian basin fisheries. Such meetings should include reviews of the current situation, e.g. river discharges and Caspian Sea water level, fish stocks and their forage base, current fisheries management measures, and they should identify areas in need of international collaboration. The meetings should also assist in the preparation of long-term strategies for further rehabilitation of fish stocks, with the purpose of maintaining their high yield. A draft outline for the first international meeting on the Caspian basin fisheries is presented as Annex 5 of this Report.

4.2 Caspian coastal lagoons, lakes and bays

The following water bodies, connected with the Caspian Sea, were visited: Astara lagoon on the Iran-USSR border. Anzali Mordab (lagoon) near Bandar Anzali, and Gorgan Bay in the southeast of the Caspian Sea. Lapoo Lake near Sari, close to the Caspian Sea but unconnected with it, was also visited.

4.2.1 Astara lagoon

This lagoon, which extends 11.4 km eastwards from Astara town, is split by a river into two unequal sections: the western section of some 50 ha, and the eastern of some 900 ha surface area. The lagoon is separated from the Caspian Sea by a sand bar. At present, the 900 ha are estimated to produce 100 t/year of fish. Backing the western section of the lagoon is a depression of some 80 ha which is to be developed for aquaculture.

During winter storms, the Caspian Sea floods the lagoon over the sand bar. The river flows during August-March at an average flow rate of 3 m3/s, with some river water entering the lagoon and reducing its salinity to about 7 ppm. During the rest of the year, there is no flow due to the river water uptake for irrigation.

The lagoon, which is very shallow, has patches of emergent aquatic plants, and extensive growth of submersed plants. It could be assumed that the rich aquatic plant growth and the shallowness make this lagoon an ideal habitat for young fish providing nursery and feeding grounds for them. There are no up-dated lists of fish species or information on their dynamics such as reproduction, growth, mortalities, and on their fishery. However, there is a plan to develop the lagoon for aquaculture. It is proposed to deepen the western part of the lagoon and to remove some of the aquatic plants. Such changes may well be in the interest of aquaculture, but they would interfere with natural restocking by fish entering the lagoon through the current connection with the Caspian Sea. This is the pattern of natural restocking which provides for the current fisheries.

Introducing aquaculture in the western sector of the lagoon would undoubtedly result in an increase in fish yield, if artificial feeding is included. The socio-economic impact of the conversion of the lagoon to aquaculture should be evaluated prior to any ameliorative measures. The preservation of the natural condition of the much larger eastern part of the lagoon, covering some 900 ha, should suffice for maintaining natural fish stocks for a sustained fishery. These fish stocks, their environment and their fishery should be carefully monitored.

4.2.2 Anzali lagoon

Anzali Mordab (lagoon) is situated in the northern Iranian Gilan Province. Its present surface area is estimated at less than 35 km2. (A more accurate estimate would require aerial photography which was not available.) The lagoon is reportedly shrinking in size. One of the main reasons is the possible uptake of water for irrigation from some of the southern inflows, leading to smaller water input, which in turn could lead to a faster invasion of such areas with marsh and aquatic vegetation. Another reason could be siltation of the shallows. The lagoon has presently large expanses of emergent reeds, especially Phragmites australis: submersed plants are dominated by Myriophyllum, and floating plants by Trapa natans.

Already in 1961/62 Vladykov (FAO, 1964) noticed a decline in the yield of the bony fishes and related it to the decrease in the level of the Caspian Sea. Some fish species run up the rivers to spawn, and with the river discharges modified by dams and irrigation uptake fish spawning grounds are being altered or are becoming inaccessible. According to Vladykov, in the 1930s, when Anzali Mordab was 4 to 8 m deep, 30 to 40 seines 450 m in length were regularly operated here. In the 1950s the lagoon was still yielding up to 5000 t of fish per year. This was followed by a gradual decline in catch. According to Vladykov, in the early 1960s, the Mordab was only about 1 m deep and muddy, which made passage difficult for migratory fish. He noticed that the lagoon was also becoming choked with aquatic plants, with large areas covered by water chestnut, Trapa natans. Cloudy and rainy weather common during spring and summer occasionally resulted in a deficiency in dissolved oxygen which caused fish mortalities. He recommended vigorous protection of the four major fish species, i.e. Kopur (common carp), souf (pike perch, Stizostedion lucioperca), sim (bream, Abramis brama) and sefid mahi (kutum, Rutilus frisii kutum).

Vladykov (FAO, 1964) pointed out the changes in fish stocks between 1933/34 and 1961/62 (Table 4). There are no recent data on fish stocks and species composition and on the use of this lagoon by semi-migratory fish such as kutum, which is known to be the most popular table fish in Iran. The current importance of Anzali lagoon as breeding, nursery and feeding ground for various fish species has to be assessed under new conditions, which have arisen as a result of the complex interaction of human activities, e.g. drainage and reduced water inputs through inflowing rivers, and from the recent rise in the water level of the Caspian Sea and hence also of this lagoon by about 110 cm above the lowest recorded level in 1977. If the rise in water level continues, the lagoon will soon flood the low-lying pastures which are currently only 20–30 cm above the sea/lagoon level. Such flooding would probably enhance the reproduction and survival of fish and lead to increase in fish stocks. It could also change the aquatic plant cover in the lagoon, perhaps resulting in more open waters due to the deepening of the lagoon. Some dredging of the non-silted over and overgrown creeks would improve access to the lagoon for semi-migratory fish and would lead to better water quality by raising the dissolved oxygen content.

The connection between the lagoon and the sea is of importance for free movement of fish. This connection, represented by a narrow canal, is built up on both banks for a distance of some 1 km. The canal receives some pollution both from the sewerage discharge and from port activities, with a number of boats using the canal mouth as an anchorage. The extent of this pollution is not known, but if it were to exceed certain limits, it could effectively function as a barrier for the fish moving into and from the lagoon.

At least two species of crayfish are found in the Iranian waters of the Caspian Sea, i.e., Astacus leptodactylus and A. pachypus. According to Vladykov (FAO, 1964), A. pachypus inhabits principally the muddy rivers of the Anzali lagoon, while A. leptodactylus is found not only in fresh water but also in the Caspian Sea up to 5–10 km offshore. Vladykov found A. leptodactylus in rivers from the Anzali lagoon to the Feridun Kenar. During the present mission, subsamples from Anzali lagoon contained only A. leptodactylus (identified by Dr.M.Furst of Sweden). The commercial catches should be monitored to confirm that no other species is present in the lagoon. Vladykov reported a small fishery for crayfish during the early 1960s, with catches during the main fishing season March-August amounting to 2000–3000 crayfish per day. The captured crayfish were shipped alive packed in grass in wooden boxes, to Tehran.

In June 1987 intensive fishery for crayfish was initiated. During the first 20 days about 10 t of crayfish were trapped. The number of baited traps being used during this consultancy was 10 000. The crayfish are exported to Turkey in refrigerated trucks but part of the catch is used for stocking selected reservoirs and lakes of Iran. Such stocking must be considered at present as experimental, as little is known about the capability of the crayfish to adapt itself to a large variety of Iranian water bodies. Inevitably, the crayfish may not succeed in some areas. A close regular check on the transferred crayfish is needed to identify the type of habitats where crayfish survive and reproduce. In Anzali lagoon maintaining a strict control on the minimum allowable size of captured crayfish (not less than 10 cm in total length from rostrum to the end of the tail (telson) and on protection of females carrying eggs is essential to prevent overexploitation of stocks and weakening of the population, which are known to increase crayfish vulnerability to diseases.

Apart from being important for finfish and crayfish, Anzali lagoon is also an important bird nesting and wintering habitat, and is an internationally listed protected wetland because of its importance for migratory birds.

Two major man-made impacts seem to disturb at present the ecological equilibrium of this lagoon: (i) the regulation of the incoming rivers and their water uptake for irrigation; this is associated with the presence of dams and weir type structures blocking the migratory path of economically important fish; (ii) the dredging attempt (now stopped) to speed up the passage of floodwaters through the lagoon and prevent water logging with the aim of obtaining more agricultural land. The attempt to ameliorate the lagoon shows the conflict of interests, i.e. to increase the area of arable land through drainage on one side, and to conserve wildlife and fishery on the other.

The situation, as at present, demands clarification of the lagoon's importance for fish and wildlife, and urgently requires putting forward proposals for the best management measures, which would make possible the optimal use of the lagoon for fish, crayfish and wildlife, while maintaining it as a unique habitat.

A project proposal for a study of Anzali lagoon productivity and fish stocks investigations is presented in Annex 4.

4.2.3 Lapoo lake

Lapoo (or Lapu) Lake near Zaghmarsz, about 20 km northeast of Sari in the central Mazandaran province, convers a total area of about 100 ha. It is separated from the Caspian Sea by a wide strip of land and therefore it is not influenced by its waters. The maximum depth of the lake is about 2.5 m, rising during winter by perhaps another 1 m. The lake is a favourite wintering place for birds. The lake is rich in aquatic plants, both emergent and submersed. The submersed plants are dominated by Ceratophyllum and Myriophyllum. Conjugate filamentous algae are common at the surface and the emergent plants are mainly Phragmites and ?Scirpus. A list of endemic fish was not available, but the predatory pike was supposed to be common. In 1985 a total of 90 000 fingerlings of common carp, grass carp and silver carp were stocked, of which 20% were common carp. In 1986, 120 000 fingerlings were stocked. In the same year, a very good harvest of all three species was reported. Without detailed knowledge of stocking rates for individual species and of harvested fish, little advice is possible. The lake is a complex system, probably well balanced. The extensive cover of emergent macrophytes may be a limiting factor for the number of silver carp which could at present be introduced, as macrophytes restrict plankton production, the major food of this fish. A higher density stocking of grass carp would facilitate a gradual decrease in submersed plants making more space for silver carp. To find the best stocking rate will require careful monitoring of catches and of the impact of the stocked fish on environment, especially on the different types of aquatic plants. As the emergent and floating aquatic plants are an important habitat of the birds wintering on this lake, while the submersed plants provide opportunities for their feeding, a compromise between the interests of fisheries and wildlife should be reached.
Soon after the visit of the consultant to the area, freshwater crayfish A. leptodactylus were to be introduced into the lake from the Anzali lagoon. Such an introduction, if successful, would increase the complexity of the habitat. Regular monitoring of the success of stocking and of mortality rates due to fish and bird predation, fishing, and occasional unfavourable water quality conditions, especially water deoxygenation, should become a priority. Interpretation of such monitoring would greatly assist in designing the best possible management measures. The preservation of Lapoo Lake as a bird wintering habitat must be included in any fish stock management considerations.

4.2.4 Gorgan Bay and its catchment rivers

Gorgan Bay is situated in the southeast of the Caspian Sea, from which it is separated by an approximately 60 km long promontory. It is connected to the sea only through a narrow passage in the east. The total surface area of the bay is approximately 400 km2. The major freshwater input into this bay is through the Kara-su in the east of the bay. This river discharges 62 million m3/year (in 1982), and the estimated-input of fresh water through all rivers into Gorgan Bay is about 150 million m3/year. Goregan Bay has the following water quality characteristics: salinity 8.7 to 10 ppt, pH 8.1–8.9, maximum temperature about 29°C.

At one time the bay supported a lucrative fishery, especially for the Kollme (Turkman vobla, Rutilus rutilus caspius). Some 20–30 years ago their catch was in the vicinity of 4000 t per year. The current catch of this species is negligible.

The rise in the Caspian Sea water level since 1977 has affected Gorgan Bay. Now, especially during winter storms, the Caspian Sea water surges over the 60 km long narrow sand spit. This has led to the destruction of several villages and to other damage. A larger quantity of sea water enters the bay than before, and this, together with the rise in water level has impacted the aquatic biota including the distribution of aquatic plants. These changes have not been recorded. It would be most desirable to initiate regular monitoring of a diversity of water quality parameters and biota as soon as possible. During the present visit, as observed from a boat, large areas of aquatic plants extended along the mouth of the Kara-su and north of it, connecting with the reed areas in front of the mouth of the Gorgan River. From there aquatic plants probably extend further to the border river Atrak, well outside Gorgan Bay. These plants must be of considerable importance for freshwater/brackish water fish stocks by providing refuge, feeding and perhaps even spawning grounds.

The drastic decline in the Turkman vobla in the coastal waters of the southeastern Caspian Sea is of a relatively recent date, with the 1978 catches being 830 t, and those for 1979 only 120 t. The floodplains on the lower course of the Atrak River are known to be spawning grounds for this fish and when there are only minor floods or no floods at all, the recruitment of vobla fails. This could be the reason for the sharp decline in 1979. Soviet scientists have recommended that discharges be regulated to maintain flooding for the time needed to allow vobla to spawn. Similar action may be necessary for the Gorgan River, where a large reservoir has been in existence since 1970, with much of the flood water now being kept behind the dam (see below).

The consultant visited a new temporary fisheries research laboratory in Turkaman near Gorgan Bay. Plans are being made for the construction of a permanent building on the shore of the bay. Two fisheries specialists (Mr.Maghsoodi and Mr.Moradi), both recent graduates from Indian universities, have taken up their assignment with this laboratory, which is part of the Fisheries Department (Shilat).

Little can be said at present about Gorgan Bay's potential for fishery development. Baseline data, if available, have to be collated and analysed, especially those which show the seasonal dynamics of water quality, biota, productivity - both primary and secondary. Plant societies should be mapped and their significance for fish assessed. Regular monitoring of productivity parameters and fish populations should be initiated. Present migrations of fish in the inflowing rivers should be assessed, as well as the effectiveness of floodplains as spawning grounds under the present level of water uptake and regulation. Proposals should then be put forward for strategies for rebuilding fish stocks to commercial quantities. Enhancement through aquaculture measures such as introduction of pens, cages, enclosures, could be also considered, as well as the need for artificial production of fingerlings in hatcheries and their regular stocking in these rivers. There is a possibility of introducing new fish species once a good knowledge of the aquatic environment is available.

The decline in fish stocks in Gorgan Bay seems closely related to damming of the Gorgan River by Vochmgir dam in 1970. As a result, floodplains on the lower course of the river probably ceased to exist, thus preventing the spawning of fish such as vobla, and perhaps common carp as well. Information on river discharges through the dam, especially during the fish breeding periods, would assist in determining weather indeed this is the major reason why the Gorgan Bay fish stocks have declined. A study of current fishing activities in the river mouth is also needed.

Vochmgir irrigation reservoir, with a maximum depth of 17.2 m and a maximum reservoir surface area of 20.7 km2, consists of several dyked basins which can be emptied independently. The management of the dam has recently decided to assist the fishery by maintaining a minimum water level of 1 m to prevent fish mortalities. Although no physico-chemical data were available during the visit, the consultant's impression was that the reservoir is a eutrophic water body, rich in nutrients and in primary production, as seen from the green colour indicating high phytoplankton densities. The present fish catch is dominated by endemic (not stocked) cyprinids, while only few of the stocked Chinese carps (the first stocking took place three years ago) are captured. In 1986, 60 tonnes of fish were harvested from the reservoir using beach seine nets in areas without underwater obstacles. The fish are sold in Gorgan town to government employees. The stocking of the reservoir continues. The current releases are in the range of 500 to 1000 per ha of 2–3 g fingerlings. Further improvement in fish production is underway in the form of introducing duck cum fish culture in the area near the main dam. The ponds for this integrated aquaculture were under construction during the consultant's visit.

Crayfish Astacus leptodactylus from the Anzali lagoon was released on an experimental basis into one of the reservoir sub-basins, but there was no survival. Among the reasons for this failure might be temperature shock due to the transfer of the crayfish from refrigerated trucks straight into the reservoir, where the water temperature was about 29°C. There is also a difference in the character of the Vochmgir reservoir and Anzali lagoon, with the former being poor in aquatic plants. If future releases are planned for this reservoir, they should be carried out on a pilot scale during winter when water temperature is low, and the crayfish should be released in vegetated areas enclosed with wire mesh to prevent the crayfish dispersing. Only after it is known that the introduced crayfish survival is reasonably high, more crayfish could be introduced on a larger scale. The crayfish should be carefully monitored for their ability to reproduce in their new environment and for the rate of survival.

About 35 km north of the Vochmgir reservoir is the Atrak River, which forms the border with the USSR. During the last years floodplains of this river have been receiving less water than needed for successful spawning of some fish, especially vobla and common carp. It has been estimated that at least 56 million m3 of water must be released during the October-June period, if natural spawning is to be successful. The present uptake of water for irrigation allows such discharges only during the years of high rainfall. If more water cannot be released for the use of the natural breeding grounds, hatchery production of vobla and carp fingerlings and their stocking is probably the only alternative for improving fisheries for these species in the Atrak and the coastal waters of the Caspian Sea.

The Atrak River salinity dramatically increases when waters of the Sambar River from Turkmenia (USSR) join the Atrak (Table 5). The consultant was informed that the Soviets are currently diverting this river to prevent its mixing with the Atrak in order to improve water quality in the latter. On the Iranian side, there are five lakes fed by Atrak waters. Four of them are freshwater, but the lowest in altitude is saline. These lakes are interconnected. To improve their water retention the lakes have been recently dyked, to make them larger and permanent. Atrak river water passes through these lakes along an altitudinal gradient, entering first the highest lake, the outflow of which enters the second lake, etc. For the chemistry of the Atrak River, and for data on Atrak lakes see Table 5. Although the lakes were not visited by the consultant it is believed that their morphological and limnological characteristics would be close to those of the Vochmgir reservoir. When water retention and lower water salinity in the fifth lake are achieved it should also become suitable for fish. Information is needed on the current status of fish stocks and proposals need to be put forward for fishery management. The consultant understood that at present, there is no fishery on these lakes. The fish stocks in Atrak lakes are probably similar to those in Vochmgir reservoir, i.e. dominated by native cyprinids. Once the fish stocks and other biota composition and water quality are known, the possibilities for increasing fish yield should be assessed. Judging from the high aquatic productivity of the Vochmgir reservoir, these shallow lakes might also achieve high production. Systematic data collection from the Vochmgir reservoir should be of great assistance in making prediction on the Atrak River lakes's fishery potential. The Fisheries Department should closely collaborate with the Vochmgir dam authority in the data collection through regular monitoring of parameters indicative of aquatic production. The duck-cum-fish farming should also benefit from such information. If this integrated aquaculture is successful at Vochmgir, it could be also considered for the Atrak River lakes.

Little is known of the Soviet activities on the Turkmenian side of the Atrak. It has been mentioned that apart from the effort to divert the saline Sambar River, a reservoir was recently created on the Soviet side, aquaculture facilities developed and a research institute is either already in existence or under construction. More active contacts between the two countries sharing the Atrak River are needed if optimal benefit is to be obtained for fisheries on both sides of the border. The ground for such collaboration could be prepared during the proposed international meeting on the Caspian basin fishery resources (see Annex 5).

4.3 Reservoirs of Caspian plains

On Caspian plains of the Gilan and Mazandaran provinces there is a considerable number of village irrigational reservoirs. Their surface area ranges between 10 and 400 ha, with a maximum depth of perhaps 15 m. Their water quality probably differs from one to another, the shallowest ones being probably more productive than the deep ones. Some have an extensive cover of aquatic plants. Their draw-down varies, and some may completely dry out during summer, when their water is drained for irrigation. Many of these reservoirs were constructed for storage of irrigation water for rice fields. Some reservoirs have submerged, or partly submerged dead trees, which are the remnants of the flooded terrestrial vegetation. Some reservoirs are stocked with fry/fingerlings of common carp and Chinese carp (silver, and to a much lesser extent grass carp) produced in hatcheries. Ivanov (FAO/UN 1971) mentioned some of the reservoirs as having natural population of common carp and pike, but according to him their numbers were insignificant and of no particular interest to commercial fisheries. No list of reservoirs was available to the consultant, and the following considerations are therefore based on the very limited number of those reservoirs visited.

The consultant visited Darband reservoir, which was formed for rice irrigation. This reservoir is situated at about 20 m a.s.l. It covers 20 to 30 ha, and its maximum depth is perhaps 8 m. Its green colour suggests that it is highly productive. The inflowing river forms a delta, which could be levelled to achieve a more uniform depth of this reservoir, which in turn would allow a more efficient use of fishing gear. The residual water could then also be maintained at an even depth over a reasonably large area, thus making it possible for fish to use the reservoir even when drawn to a minimum retention volume. The high density of planktonic algae is suitable for silver carp if stocked. During the visit, the reservoir was full of frogs and snakes, and the surface was partially covered in duck weed.

Abas-Abad reservoir, situated about 3 km downstream from Darband reservoir, covers some 137 ha when full, and has a maximum depth of 8 m. It appears to be highly productive, undoubtedly as a result of some fertilizer input from fields situated upstream. The reservoir is supposd to be completely drained by July or August, without leaving even a minimum of residual water which would allow fish to survive. This large, shallow water body appears ideally suited for fisheries, but present negotiations on such use between the fishery authorities and the owners of the reservoir have not yet led to a successful solution for the multiple-use of this reservoir. Maintaining a 1 to 1.5 m residual water depth would result in substantial annual harvest of fish which could fully benefit from the warm period of the year. Under the present water use conditions this is not possible.

Another reservoir of some 15 ha surface area was seen in the hills near Rasht. This reservoir, full of tree stumps, is fairly deep and the presence of standing dead trees prevents the use of moving fishing gear. For some time the reservoir has been stocked with silver and common carp provided by the Jehad hatchery. The Jehad organization has also fertilized the reservoir to increase the aquatic productivity. Successful management of the reservoir will require the removal of tree stumps at least in selected areas along the reservoir shoreline, to make possible the application of moving gear such as beach seines. A pilot study with cages stocked with fish would show whether such a method could be applied, without - or with - artificial feeding. Setting up cages in a shallow cove, which could be separated from the rest of the reservoir by block nets, would considerably increase fish yield if fish in cages were fed, as any unutilized food from cages would be made available for fish stocked in the blocked off cove. All fish could be easily harvested. In Hubei Province, China, a study on the combination of fish cove and cage culture in Dan Jiang reservoir under conditions as described above, gave a total net yield of 5740 kg/ha. Under Chinese conditions, this approach was also economical (X. Lu, personal communication).

Present stocking of a great variety of small water bodies in Gilan, Mazandaran and some other provinces is still a rather uncoordinated activity, with no guidelines available on the best mix of fish species or on stocking rates. The results of stocking suffer from the lack of monitoring, which could be later used in improving the stocking strategies. The density of stocking is determined by the availability of fry/fingerlings from hatcheries. Predominantly small-sized (2–3 g) fingerlings are stocked, which are vulnerable to predation and other impacts causing high mortality. For some reservoirs catch data are available and these should be carefully evaluated. The shortage of experienced manpower will prevent regular monitoring of stocked water bodies for some time to come. Some catch statistics could, however, be collected with the help of local fishermen, and such data, together with the record of species number and weight stocked should then be assessed for the level of success. Then stocking rates should be adjusted accordingly. Collection of data for a comprehensive inventory of all small reservoirs should also be initiated. For each water body, such data should provide information on: altitude in which situated, surface area (maximum and minimum, whether the water body periodically dries up, water level fluctuations), depth, water quality, shoreline configuration, presence or absence of tree stumps, aquatic plants and their cover (submersed, emergent, floating), and some indication on the present level of planktonic, benthic and fish production. A list of local fish species, indicating the abundance for each species, should also be provided to allow the assessment of any possible interactions between the introduced and local fish. Such an inventory would make it possible to group water bodies into fishery development potential categories, and help in identifying those unsuitable for fishery enhancement through stocking. This would result in saving stocking material which might otherwise be wasted if stocked in unproductive or otherwise unsuitable water bodies.

The effectiveness of stocking can be determined from the correlation between stocking and catch. Such dependence can be calculated only when the sets of data on stocking and catch are long enough, i.e. stocking is not sporadic. Leopold and Bninska (1987) have drawn a set of valuable observations from long-term monitoring of fish stocking in Polish lakes and reservoirs. In most cases when they found a significant correlation between stocking and catches of a given species this was not linear. This is quite understandable considering the fact that biological phenomena are very seldom if ever of a linear character. The relationship is often of a curvilinear character. In most cases there was a certain minimum and maximum effective stocking rate; in other words a too low or too high stocking rate produces hardly any effect, and in the latter case the fish catch might even decrease. The curves of dependence between stocking and catch can be directly used to formulate management decisions. Since the curves are specific for each ecosystem, the analyses must be made separately for each water body or each aquatic ecosystem. Leopold and Bninska stressed that there exists at present no clear-cut guide to advice on what stocking rates provide the highest fish yields.

The complexity of environmental factors still makes such predictions difficult, although there are certain conditions which are predictable. For example, if a natural water body has a population of predatory fish, only large-sized fingerlings should be stocked. The morphometric features of the water body, combined with dissolved mineral levels, usually determine the overall productivity level : the higher the concentration of dissolved minerals (to a certain level) and the shallower the reservoir, the more productive such a reservoir will be. The presence and absence of aquatic plants is of importance for some species as spawning substrate, nursery zone and feeding area. Young fish will escape to hide from predators in such plants, and the decaying parts of plants will provide direct food to a number of aquatic organisms such as crayfish and fish. For Africa predictive models using simple environmental parameters are now available, which allow one to obtain an idea on the potential fish yield for new reservoirs. Among these fish yield prediction using the morpho-edaphic index (Marshall, 1984) has been widely used. When more data are available, this model could perhaps also be adapted for the Middle East arid countries.

There are many cases when it is impossible to calculate the dependence between stocking and catch because the results are not significant. This usually happens when stocking and/or catches are very variable and/or irregular.

4.4 Migratory fish of commercial importance

Apart from sturgeon, two species of indigenous Iranian migratory fish of the Caspian basin are reproduced in hatcheries and their fingerlings released into rivers flowing into the Caspian Sea. These are mahi azad (Farsi), the Caspian salmon (Salmo trutta caspius), and mahi sefid, kutum (Russian) (Rutilus frisii Kutum). A third species, kollme, vobla (Rutilus rutilus caspius) is hatchery-produced in the USSR.

4.4.1 Mahi azad, Caspian salmon (Salmo trutta caspius)

This fish enters the Caspian basin rivers of Iran and the USSR. According to Kazancheev (1981) the fish enters the rivers almost one year before spawning, with poorly developed gonads. The breeding migration takes place at water temperatures of 7–9°C, between November-February. In the Iranian rivers the fish reaches 53–103 cm. It matures at the age of 3–7 years, and it reaches 7 kg in weight. The average length of 82 cm is reached when 4 years old. In Iranian rivers, the Caspian salmon's fecundity is 2 100 to 13 500, with an average of 7 050. Eggs are released from October until January, and they hatch after 30 to 50 days. While in the USSR in the Kura River the brooders die after breeding, in smaller rivers they are known to breed up to six times. In the USSR, the catches declined from 400 t in 1936 to 5 t in 1970, and the fish is now artificially spawned, as a result of which the number of fish in the rivers has been gradually increasing.

The Bahoner trout propagation farm at Kelardasht, at an altitude of about 1 400 m a.s.l., was established on the Sandar-Rud, which drains the high Elburz Mountains and ends in the Caspian Sea. The Bahoner farm specializes in the production of the Caspian salmon and rainbow trout. In the Sardar-Rud the Caspian salmon migrates about 15 km and in some other rivers up to 50 km upstream. The brood stock captured for spawning amounts to about 200 fish, and these are captured in the mouth of the rivers - one population in the autumn, another in the spring. With an average fecundity of 2 000 eggs per female, the annual egg production is about 400 000. From these, about 130 000 fingerlings are produced annually, but it takes two years before the fingerlings reach weight of 15–20 g, corresponding to a length of 10–15 cm, which is considered suitable for their release. The Bahoner farm production of Caspian salmon and rainbow trout combined was 1.8 million fingerlings in 1985, and 1.7 million in 1986. Caspian salmon is totally protected, but due to the poor enforcement it is heavily fished, both as adults and as freshly released fingerlings. As there is no marking/ recapture of the released stock and no experimental fishing, there are no data which would indicate how much the present stocking contributes to the preservation of this now rare species of fish.

The second major task of the Bahoner (Kelardasht) cold-water fish farm is the production of rainbow trout Salmo Qairdneri, of which in 1987 2.5 million fingerlings were produced in 1987. From this production, one million were released into three reservoirs: Karaj and Lar near Tehran, Doroudzan (Fars Province), and into the Zayandeh-Rud in Mazandaran Province. Lake Lasem in the same province is also stocked from the Bahoner farm. 1.5 million fingerlings are sold to private farmers, at a cost of R 20 for a one 1 g fingerling. Each one gramm increment increases the price by R 2. Five months old fingerlings reach a length of 10 cm and weigh 4 to 6 g. The Bahoner fish farm has physico-chemical data on water of the stocked reservoirs and the lake, but no information on the success of these releases. The on-going construction of the farm extension will alleviate the stress from the currently very high densities of fingerlings and broodstock at the farm. The extension will also make it possible to produce 50 t of market-size rainbow trout.

4.4.2 Mahi sefid, kutum (Rutilus frisii kutum)

This is a very popular fish in Iran. It inhabits the Caspian Sea and migrates into rivers and lagoons of Iran and the USSR to breed. It breeds in shallows with aquatic plants and slow current, in a depth of about 0.8 m. The sticky eggs are attached to aquatic plants or to gravel on a stony bed. The fish spawns in March-April at water temperature of 13-15°C. The young migrate downstream, the migration ending in August. In the sea they feed on molluscs and crabs. In its fourth year, when it matures, it reaches an average length of 41 cm (Kazancheev, 1981). The stock have drastically declined both in Iran and in the USSR, most probably as a result of river regulation. In Anzali lagoon there were only 85 kg captured in 1961/62 as compared to 1363 tonnes captured in 1933/34 (Vladykov, in FAO, 1964). For a number of years, Iran and the USSR have been producing fingerlings in hatchery conditions and releasing them into streams. In Iran, mahi sefid has been produced in the Sad-e-Sangar (Beheshti) and Siahkal fish farms on the lower Sefid-Rud in Gilan Province. The production of fingerlings in hatcheries has grown from 38 million (1985) to 51.7 million (1986). Fingerlings are frown in ponds to 2–3 g weight and then released in the Sefid-Rud which carries them into the Caspian Sea.

In the Samur River in Dagestan (USSR), near the border with Iran, mahi sefid fingerlings of 1.5 – 5 cm length and a mean weight of 615 mg start entering the sea towards the end of May at water temperatures of 20–22°C; this migration (passive transport downstream) lasts until August. The most intensive migration takes place at the end of June. It is estimated that 100 to 200 thousand broodfish enter the spawning sites of the Samur River (Magomedov et al., 1987). The available information on the size of broodstock populations, surface area of spawning grounds, and on the number of fingerlings now makes it possible to put upper limits on fish catches for this species. At present, catches of Kutum along the Dagestan coast reach 25 to 30 t/year. An increase can be reached though enlarging spawning areas and by hatchery production of fingerlings for release in natural waters. Magomedov et al. (1987) recommended that water passages through marshes be regularly cleaned of aquatic plants to maintain water flow over the spawning areas. Neglected overgrown and silted spawning and nursery grounds are the major reason for the reduced quantity of kutum spawn, as observed for example in the Terek River (Akhmetov, 1986). A similar situation has probably developed in the Anzali lagoon during the last years and contributed to the decline in kutum there. To rehabilitate the Anzali stocks of kutum would require better understanding of the present conditions there for spawning of this fish. A controlled reduction of aquatic plants with the objective of improving water flow and dissolved oxygen content could be achieved by introducing aquatic plant eating fish. Such an ameliorative measure should assist in the rehabilitation of the lagoon for kutum spawning and for its use as nursery and feeding grounds.

4.4.3 Kollme, vobla (Rutilus rutilus caspius)

This species is present in the southeastern part of the Caspian Sea, i.e. in the coastal waters of Iran and Turkmenia (USSR). Along the eastern coast of the Caspian Sea it is fished as far as Bekdash, north of Krasnovodsk. It is a migratory fish which enters the Iran-USSR border river Atrak for spawning. It also enters other Iranian rivers south of Atrak. In the Atrak, the breeding migration starts in January-February, and lasts till April. The most intensive migration takes place at water temperatures of 10–12°C and extends over 20 to 25 days. The migration ends about 70–80 km upstream from the river mouth. After spawning, first females, then males migrate back to the sea. The fish grows slowly, reaching a median length of 19.3 cm in its fourth year (Kazancheev, 1981). However, even one year old fish (9–11 cm long) may become mature. The eggs are released starting in February, with peak spawning in March at water temperatures of 15–18°C. Spawning grounds are the floodplains of the lower Atrak. If there is no flood, no spawning takes place. The number of kollme could be increased by regulating the discharge to provide the needed flooding of spawning grounds. For more information see Section 4.2.4.

4.5 Non-migratory stocks

River regulation and intensive fishery has also led to a decline in common carp stocks of the lower reaches of Iranian rivers and in some lagoons of the Caspian Sea basin. The Turkmenian form of the common carp has its feeding grounds in the coastal waters of the Caspian Sea. During winter the fish enters the mouth of the Atrak, where it spawns between Feburary and April. The young fish are carried downstream into the sea. This downstream ‘migration’ ends in July, when no more water flows through the river. When there is no flood, there is no spawning, and gonads become resorbed. It has been pointed out by Asanov (1986) that the latest decline in catch has been due to the failure of spawning in 1984, and he cautioned that this could result not only in the loss of the carp as a fish of commercial importance, but also in the loss of a chance for its recovery. As this fish is of commercial importance both in the USSR and Iran, it is essential that measures are taken to rectify the decline in common carp stocks in the southeastern Caspian Sea. Asanov (1986) has put forward proposals for a number of measures needed for the rehabilitation of carp fish stocks: rehabilitation/ reconstruction of fish passes so that the broodstock can reach spawning areas; construction of a reservoir to provide for timely water releases for flooding spawning areas during the years of low discharge; enforcement of catch limits. Hatchery/ farm fingerling production and stocking of common carp and bream (Abramis brama) has been practiced in the Volgo-Caspian region for some years, and it is estimated that the stocked and harvested fish has contributed 17–30% and 19–20% respectively to the total commercial catches of these two species in this region. Hatchery produced fingerlings of common carp when stocked in the Gorgan and Atrak rivers, should be carefully monitored for their rate of survival.

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