The following major project activities were carried out:
Regular supervision and guidance to the national staff were provided by the two consultants during their missions. The assistance given to the consultants by both the NPD and NPS, as well as by national staff of the FRC in Bandar Anzali proved invaluable. The major shortcoming during the whole project life was the delay in delivery of equipment through customs in Teheran Airport and the loss of much of the equipment at Rome Airport. Of 37 items of equipment covered by the UNDP contribution only 15 were delivered by the end of the project. Consequently, some project objectives were not achieved (e.g., analysis of the growth in weight of fish and crayfish).
Data on phytoplankton, zooplankton and macrozoobenthos are estimations only as the absolute lack of reliable literature, ignorance of the Russian language and lack of experience only allowed the national staff to divide the samples into main systematic groups.
The NPS were trained by the FAO consultants in various field and laboratory procedures and in the use of equipment. On-the-job training involved collection of catch and effort data, fishing using fyke nets and electrofishing equipment, marking of fish with tagging gun, sampling of fish scales and measuring of fish in the field, fish species identification, statistical analyses, fish-scale reading including the identification and measurement of annuli, discerning the false annual rings and the juvenile marks, back-calculation procedures for determining growth in length of fish, and calculation of von Bertalanffy's equation of fish growth in length. The NPS were also trained in simple methods for estimating the lagoon surface area from the map. National staff of the chemical laboratory were trained in: methods of sampling and analysing various chemical components in the surface, rain and ground water; quantification of the vertical distribution in sediment of the coarse particulate organic carbon; use of the litter bag method to measure the decomposition rate of macrophytes; in situ respiration of decomposing macrophyte detritus; and also in methods of calculating the river nutrient load budget, apparent and total respiration of a plankton community and in measuring primary production. It was felt, however, that this on-the-job training was not sufficient and should have been complemented by a special training course in ichthyology and fishery biology, as the educational background of the national staff is generally low.
Mr Nurdin Hosseinpour, the national project director, and Messrs Mohamed Karimpour and Davoud Haghighi, the national project staff, undertook a study tour to Italy to familiarize themselves concerning management of coastal lagoons. They visited several lagoons and/or aquaculture facilities of various types in southern and northern Italy and also attended a seminar dealing with aquaculture research with particular reference to lagoon aquaculture. Participants learned much and appreciated this study tour organized for them by FAO and Italian aquaculture organizations and companies.
Anzali Lagoon (Appendix 1) underwent considerable changes over the period 1929–89. First, its open water area greatly decreased, and in 1989 it represented only about 22.5% of the open water area estimated for the late 1930s (Fig.3). It is noted that the open water in 1989 was slightly more extended than in previous years as a result of the rising Caspian Sea level, which also caused a rise in the Anzali Lagoon level. Although no measurements are available after 1989 and nor was it possible to obtain aerial or satellite photographs of the area, observations from a boat showed that in summer 1991 the Lagoon already flooded most adjacent pasture and rice-fields (Fig. 4).
The rising level of the Caspian Sea (Figs. 5,6) has led to an increase in water salinity (Fig.7), which in turn has resulted in the decline of submergent and emergent macrophytes, and in increasing numbers of marine and brackish water invertebrates and fish. Since 1989, organisms such as the polychaete worm Nereis diversicolor, the barnacle Balanus eburneus, the crab Rhitropanopeus harrisi, the mollusc Mytilaster sp., the fish Atherina mochon, Alosa caspia, Liza auratus, Syngnathus nigrolineatus and even Clupeonella cultriventris started to appear and have been increasing in numbers. This suggests that until about 1940 the Lagoon must have been a brackish water coastal bay; then it gradually transformed to a purely freshwater basin and is now returning to its former brackish water state.
Although there are no exact data on the water quality prior to 1973, when salinity was recorded in the Lagoon outlets by Kimball (1973), there are many indicators that in the past the salinity of the Lagoon was considerably higher and that this waterbody, which now represents a freshwater marsh lake, was formerly a brackish water basin with salinity around 6% or even higher. The evidence of this is the presence of shells of Cardium edule, a marine mollusc which was collected during the present study in mouths and lower courses of the Bahambar, Kolsar, Massuleh, Siahdarvishan, Pasikhan and Pirbazar Rivers. Other indicators are statistical records for the beginning of the 1960s of the catch of shad (Alosa caspia) and what the old fishermen and others remembered. For instance, a 65-year-old fisherman, Rajab Sayad Ghanbari, who had fished in Anzali Lagoon since mid-1940s remembers that the water in Anzali Lagoon was not drinkable even in the mid-1950s because it was salty. Historical reports also confirm the formerly brackishwater status of this lagoon. So Il'in when describing (1927) the fisheries in northern Iran and the fishery for kutum in the Anzali Lagoon explicitly writes (p. 105): “Northern winds backing the water in the channel (= outlet in the present Bandar Anzali harbour; note by Holčík) and even evoking the backward current from the sea into the bay, quickly interrupt the migration of this fish…”. On the same page he also writes that, in 1914, the Caspian Sea waters backed the water flowing from the lagoon for 54 days. Figure 5 shows that in 1914 the Caspian Sea level was more than 3 m higher than in 1977. The reason why the backwater currents from the sea are not so evident as at the beginning of this century may be seen in the changed elevation of the Lagoon. From the statement by Il'in it may be deduced that the lagoon level was lower than that of the Caspian Sea. At present, however, the situation is the opposite and, according to the topographical survey made in November 1991, (Mohammed and Moghadm, 1991), the Anzali Lagoon water level is higher by 18 cm than that of the Caspian Sea. The reason for this will be explained later. It should be stressed, however, that because of the continuous rising of the Caspian Sea, its level in next one-two-years will be higher than that in the lagoon. Consequently the open water area of the Anzali Lagoon will continuously expand and also the sea water intrusion will be more evident. Actually, peasants from villages adjacent to the lagoon are reporting that in past few years the lagoon's water started to inundate their ricefields and pastures. Rapidly rising Caspian Sea water (Fig. 5) now threatens cities around its shores. In Bandar Anzali, for instance, buildings along the coast which were 50–100 m inland in 1989 are now threatened by the sea. Buildings along the Nahang roga now have their basements flooded. In other regions of the southern Caspian Sea the situation is the same, and in Turkmenistan the eastern coast of the Caspian Sea was declared a disaster area as rapidly rising water threatened towns and industrial complexes close to the shore (Rich, 1991). Therefore the freshwater character of Anzali Lagoon can be considered as being only a temporary phenomenon, a short episode which lasted 30–40 years and that the Lagoon has now gradually reverted to its greater surface area and elevated salinity.
Project investigations show that the Anzali Lagoon shrinkage observed since early 1930s is intimately connected with the parallel decline in the Caspian Sea level. The reduction in the surface area and also depth of the lagoon (see later) were a result of the continuous decrease in level of the Caspian Sea from 1929 to 1977 (Fig.6). During this period the extensive shallow southern (Shiakishim) and eastern (Sheyjan) basins of the Lagoon were exposed as a result of the drop in water level. They successively dried out and were then converted to rice-fields and pastures. The deeper area became so overgrown by emergent macrophytes that both the southern and eastern basins of the lagoon are totally unsuitable for fish. At the same time, as a result of the decline in the Caspian Sea level, extensive erosion took place in all channels of the inflowing rivers and they became progressively deeper both in outside and in the Lagoon. The relatively deep western basin (Abkanar) of the Lagoon dropped from 8 to 11 m in the late 1920s (Vladykov, 1964) to 1.0–1.8m depth in 1974–77 (Kimball and Kimball, 1974). The bottom of this western basin, formerly covered by sand and gravel, became overgrown with submerged vegetation. This in turn brought about an accumulation of fine sediments, largely as a result of macrophyte decomposition. The sandy bottom has been gradually replaced by a muddy one. Old fishermen repeatedly reported that still in the late 1940s and early 1950s the Shiakishim and Seyjan regions were aquatic plant-free basins with sandy bottom and both accessible for beach-seining. Because the river channels passing through the Lagoon were, and still are, deeper than the adjacent lagoon, some suspended sediments are being deposited along the submerged banks. This has contributed to the isolation of the western basin of the lagoon to such an extent that now sediments no longer enter the Lagoon here. Measurements carried out during the project show that about 87% of the sediments are now carried through the outflows (rogas) to the harbour where they have to be regularly dredged. The annual sediment load in the incoming rivers appears to be much lower than that previously estimated. The estimate given by Soviet experts in 1965 was 5.6 million. This was based on data obtained from “… similar rivers in the Soviet Union and on short-term observation on the Safid-rud river…” (Hydrorybproject 1965, p.4). Current estimates of only 386 602 t based on sediment load measurements in eleven major streams entering the lagoon almost correspond to the volume of sediments actually dredged out from the harbour (314 510 t = average annual amount for 1976–90; Appendix 2). Sediments carried by inflowing rivers thus bypass the western basin without entering it. The old sediment of sand and gravel is now covered by fine sediment rich in organic matter and originating from the decomposition of aquatic plants growing there.
The total annual load of nutrients for the eleven streams entering the Lagoon is 4 898 t of nitrogen and 378 t of phosphorus. Much of this is transported directly to the sea through the Lagoon's outlets, while about 38% remains in the Lagoon. This amount is mostly utilized by macrophytes as can be seen from the chlorophyll a data. The winter and spring average of chlorophyll a in the eastern (Shiakishim) and southern (Seyjan) basins of the lagoon fluctuated from 0.4 to 2.0 mg.m-3 and in the western (Abkanar) basin from 1.2 to 2.8 mg.m-3 respectively. Summer averages for the same were 5.6 mg.m-3 and 9.3 mg.m-3 and only in the western basin of the Lagoon did it reach 105 mg.m-3 (Fig.8). The overall annual average for the Abkanar, Seyjan and Shiakishim regions and for the rogas is 38.49, 6.05, 3.33 and 5.86 mg.m-3 respectively. These values indicate a very low phytoplankton production.
However, comparison with data by Kimball and Kimball (1974) for the period 1973–74 clearly indicates the improving conditions in Anzali Lagoon. Their figures on the chlorophyll a for the western basin and for rogas fluctuated between 0.9 and 29.4 with average 5.97 mg.m-3 and between 0.1 and 17.5 with average equal to 1.98 mg.m-3 respectively. That is, the phytoplankton production expressed in chlorophyll a values in the western basin and in outlets in 1990–91 was by 6.45 and 2.95 times higher than in 1973–74. This also indicates the retreat of submerged and floating macrophytes and the increase of algae. Open-water algal blooms were occasionally observed, for example in summer 1991, when the filamentous blue-green alga Anabaena bloomed in the Abkanar region.
The low phytoplankton production is reflected in the very low biomass of both zooplankton and macrozoobenthos. A rough calculation of zooplankton biomass, using the average individual weights given by Vranovský (1974), as 0.00146 mg for rotifers, 0.01865 mg for cladocerans and 0.003435 mg for copepods, gives the total weight/litre as 0.1327, 0.0942 and 0.1656 mg respectively. The total zooplankton biomass for western basin equals 0.3925 mg.l-1 or 392.5 mg.m-3. Comparison with the Kimball and Kimball (1974) data for the Anzali Lagoon from 1973 to 1974 is not possible, as their counts represent the total zooplankton including protozoans. The average calculated from these figures is almost 71 000 individuals/litre. If this estimation is correct, the zooplankton abundance and biomass is almost three times as high as in the 0–25 m horizont in the southern Caspian in 1934 (Zenkevich, 1963), but it is more than 17 times lower than in some arms of the inland delta of the middle Danube (Vranovský, 1974). The quantity of zooplankton in incoming rivers and rogas is much lower, averaging 56 and 77 individuals/litre. The density of zooplankton in the Anzali roga, draining the western basin, corresponds to the situation of the latter with average abundance 173 ind.l-1.
Zoobenthos is also low in numbers and biomass. It increases with the increasing distance from the sea. The total average numbers of zoobenthos in the harbour, outlets, western basin of the lagoon and in two inflowing rivers (Siahdarvishan and Bahambar) for the period 1990–91 were 373, 380, 723 and 930 individuals/m2 per square meter. Outlets are dominated by polychaetes and oligochaetes, the abundance of which was 37 and 31% of the total respectively. The open-water channels of the overgrown southeastern and eastern basins of the lagoon are extremely poor in zooplankton, and in the channel bottoms there are no benthic macroinvertebrates; these only occur in high densities in streams and leaves of aquatic plants.
The western basin is far more important for resident fish. A rough estimate of the biomass of the whole western basin, using the data on the weight of particular groups given by Mordukhai-Boltovskoi (1954) or those derived from Zenkevich (1963), is about 13 g.m-2 which is almost 10 times lower than in the southern Caspian (121 g.m-2; Zenkevich 1963). Soviet data for the western basin (Hydrorybproject, 1964) show only 3 g.m-2, which is substantially lower than the estimate of the authors. The macrozoobenthos biomass of the Malyi Kyzylagach Bay of the Caspian Sea in Azerbaijan, which seems to show a similar fate as that of Anzali Lagoon as it was transformed into a freshwater basin after 1955, varies from 4.7 to 7.9 g.m-2 in June (Epshtein 1962), which is also comparably lower than the authors' estimates for June 1990 and 1991 showing 15.3 and 12.9 g.m-2 respectively. Insects are the major component in the western basin as they constitute almost 84% of the total biomass. This group is dominated by chironomids which with 11.3 g.m-2 represent 83.7 % of the total zoobenthos biomass. Other groups are less important: the share of worms, gastropods, bivalves and crustaceans in 1990–91 was 5.6, 5.6, 4.6 and 0.5% of the total biomass respectively. Biomass of Nereis with 0.3 g.m-2 is still low. However, it can be expected that with the increasing size of the lagoon and its salinity the biomass of Nereis will increase and this worm will become an important food for the benthos-feeding fish species.
In spite of the fact that the zooplankton and zoobenthos values are only approximate, they correspond well to the low productivity indicated from the chlorophyll a measurements. Comparison with the data from Hydrorybproject (1964) and Kimball and Kimball (1974) indicates some recovery of the environmental conditions in Anzali Lagoon. This seems to correlate with the increasing Caspian Sea level, intrusion of the seawater into the lagoon, subsequent expansion of the open-water surface and increase in dissolved oxygen values.
Dissolved oxygen concentrations indicate the difference between high and low water quality in the lagoon (Figure 7, Appendix 3, Table 5). They also determine the presence or absence of certain groups of organisms. High dissolved oxygen concentrations were found only in the western basin, while in the southern and eastern basins the dissolved oxygen values were mostly less than 3.4 mg.l-1. In autumn the dissolved oxygen concentrations also declined in the western basin but never to such low levels as observed in the other basins of the lagoon.
The location, type, total load and levels of industrial, domestic and agricultural pollution were identified in order to evaluate their impact on aquatic life, especially on fish. There is little industrial activity in the lagoon's watershed as only 10.5 percent of the total population of the watershed work in industry (Table 9). The overwhelming majority of industrial activity is concentrated in the subcatchment of the Pirbazar and Siah rivers. But even there the heavy metal concentrations measured in the domestic, agricultural and industrial effluents are low and well below the maximum permissible level for fish (Appendix 4, Tables 12, 13). However, the increasing rate and role of industrialization in the watershed of Anzali Lagoon (Table 10, 11) will require strict pollution controls, because most of these elements are being adsorbed on sediments and detritus. The long water retention time and the low dissolved oxygen concentrations in the overgrown southern and eastern basins of the lagoon may lead to accumulation of heavy metals and contamination of fish in the long term.
About 48% of the total population of the watershed is employed in agriculture (Table 9), which largely concentrates on rice culture. The current rate of pesticides applied in rice fields is 2.5 kg.ha-1 (Appendix 5, Table 14). Much of it, i.e., 1.6 kg.ha-1, is the insecticide Diazinon. Due to its moderate stability and rapid decomposition rate, this load does not represent a direct danger to fish. Also the herbicide load is rather low and currently amounts to 0.95 kg.ha-1 of both Paraquat and Glyphosite which are not harmful for fish. These herbicides have low toxicity. Nevertheless, it is recommended that agricultural officers collaborate with fisheries personnel in ensuring proper control on dispersal of both insecticides and herbicides during their application.
The sediment (Appendix 2, Tables 3, 4) and nutrient (Appendix 6, 7, Tables 15–17) loads have no direct harmful impact on fish. It is the organic carbon that has the most adverse impact on the Lagoon (Appendix 8, Tables 18–20). A bi-weekly year-long survey of the organic matter load in form of organic carbon in eleven streams entering the lagoon shows that most of it is produced by livestock (295 981 t), followed by food processing industries (35 000 t) and human population (55 237 t). Mostly carried by the Pirbazar River into the lagoon, it significantly contributes to the poor oxygen conditions in the southern basin of the lagoon (Fig. 9). The autumn-shed leaves produce an annual load of 291 456 t of organic carbon in the forested area of the watershed; however, little of it reaches the lowlands, through the rivers.
In summer 1990 the Azolla filiculoides fern was discovered in Anzali Lagoon. In 1986 the Ministry of Agriculture initiated the introduction of Azolla from the Philippines and Azolla was then cultivated in Northern Iran. The plant was introduced as an additive to cattle feed and rice cultivation and eventually reached the Lagoon probably from the ricefields during spring floods. While in August 1990 only a few scattered plants were seen, already in November 1990 and again in April 1991 some channels and open waters in the eastern basin became covered with extensive mats of Azolla. In October–November 1991 the Azolla invaded the entire lagoon except for its western basin, where wind prevented its growth. At present almost all sheltered open-water areas in the southern and eastern basins are covered by a dense mat of this fern which also penetrated deeply into the Phragmites stands. Some channels of the southern basin are completely covered by Azolla, and in sheltered places it forms thick carpets up to 20 cm deep making boat passage very difficult. Azolla is being continuously washed down from the lagoon into the sea where it may be found along the beach several kilometres eastward and westward from Bandar Anzali.
Azolla is well known for its very high nitrogen fixation capacity. Using data from literature and estimates of area covered by Azolla, the calculated Azolla annual nitrogen load is a high 110 kg-ha-1 (Appendix 9). Part of this load leaves the lagoon especially during the spring and autumn floods. The bulk of Azolla production remains trapped amongst the reeds and in sheltered open-water areas, thus contributing to the nitrogen input after starting to decompose.
The Azolla invasion is important in its positive and negative impact on the Anzali Lagoon ecosystem. It represents a significant contribution to food resources for the herbivorous fish, especially for the introduced grass carp, Ctenopharyngodon idella. It is utilized not only by fish stocked into the lagoon but also in the new experimental pen facilities constructed on the Anzali Lagoon near Gluga. Daily, 400–500 kg of fresh Azolla is used as feed for the grass carp stocked at a density of 800/ha. The net weight gain of fish in 5 months was 800–1 200 g. But Azolla fern has an adverse effect on the Anzali Lagoon ecosystem by increasing the nutrient load and thus contributing to eutrophication of this waterbody. Dense Azolla mats prevent light penetration in open-water areas, which causes oxygen deficiency in the southern and eastern basins and worsens the already poor life conditions for fish there. The further fate of Azolla in the Anzali Lagoon remains unclear assuming that the salinity of this waterbody will increase. Information concerning the tolerance of Azolla to salinity is still incomplete. According to Van Hove (1989), Anabaena is more sensitive to salinity than Azolla and this allows the production of Anabaena-free Azolla, which is inefficient with regard to nitrogen fixation. Anyway, the problem of Azolla in the Anzali Lagoon should be carefully investigated with regard to adoption of respective measures to prevent its further population explosion and subsequent invasion to other parts of the lagoon.
The Anzali Lagoon is a relatively well-known waterbody from the fishery point of view (Appendix 10). The data are, however, mosaic, and incomplete, particularly regarding the fish community structure.
Investigations carried out during the IRA/88/001 Project showed that the Lagoon and its watershed are inhabited by 13 families, 33 genera and 41 species of fish (Table 22). Twenty-four species inhabit only freshwater, six species are marine and eleven species occur both in freshwater and the sea. The ichthyofauna is dominated by Cyprinidae which are represented by 23 species, i.e., 56% of the total number of fish species found in the watershed, while the remaining 18 species or 44% are represented by Gobiidae (4 species), Clupeidae (2), Cobitidae (2), Percidae (2) and by Anguillidae, Atherinidae, Esocidae, Mugilidae, Petromyzontidae, Poeciliidae, Siluridae and Syngnathidae, with one species each. Seven species (Aristichthys nobilis, Carassius auratus, Ctenopharyngodon idella, Gambusia holbrooki, Hemiculter leucisculus, Hypophthalmichthys molitrix and Liza auratus) are exotic species, i.e., not native to Iran, and they were intentionally (Chinese herbivorous carps, mosquitofish and mullet) or accidentally (German carp and the common sawbelly) introduced.
With 31 species of fish, Anzali Lagoon is very rich in species as its environment allows the occurrence of both limnophilous and potamophilous species along with both freshwater and marine fish. Most species are found in its western basin. The eastern and southern basins are poor in fish species with only Carassius auratus, Esox lucius, Tinca tinca and Proterorhinus marmoratus. These species were recorded rather rarely in channels with slow-running water. Large areas covered by submerged and floating vegetation are inhabited by numerous and dense schools of Gambusia holbrooki which occur only at the water surface, while the deeper layers and the bottom have no fish. Outflows from the lagoon with higher salinity are inhabited by marine and brackishwater species such as Liza auratus and Atherina mochon pontica which were found also in the mouths of some of the inflowing rivers. Syngnathus nigrolineatus was found in large numbers in the deepest part of the western basin in the front of Abkanar village and in the outlet (Sowsar roga) from the lagoon, where the salinity is higher. Migratory species, such as Rutilus frisii kutum, Vimba vimba persa, Barbus capito, Chalcalburnus chalcoides iranicus and Alosa caspia persica were recorded only seasonally and in small numbers in the western basin, although they were abundant there in the past (Appendices 10, 11). These species occur and are fished mostly in outflows and in the inflowing streams during late winter and in spring months.
In the incoming streams 23 species of fish were found, including Clupeonella cultriventris, which was not recorded in the lagoon before. Future investigations may reveal even more species. Some species, such as Alburnoides bipunctatus eichwaldi, Alburnus charusini hohenackeri, Alburnus filippii, Barbus lacerta cyri, Capoeta gracilis gracilis, Noemacheilus angorae and Neogobius kessleri gorlap were found exclusively in streams. As the taxonomic status of gobies found in Anzali Lagoon and its watershed is not yet clear, it will be treated separately elsewhere. It should be mentioned here that N. platyrostris constructor, which is found in the Black Sea watershed, and in the upper and middle sections of the Kura river, in the Caspian Sea Basin, (Pinchuk, 1977), is very adaptable. It has been sampled both in the brackish- and fresh-waters of the Lagoon, and in the headwaters of the Massuleh river in sites with current velocities exceeding 2 m.s-1, thus resembling the habitat of the European species of the genus Cottus.
In the outlets of the Lagoon were found 23 fish species but their number may be higher. Apart from marine or brackishwater species such as Alosa caspia, Liza auratus, Atherina mochon and Neogobius platyrostris, Alburnus filippii was also recorded. This was reported to dwell only in freshwaters (Berg, 1948–1949; Abdurakhmanov, 1962).
Fish distribution in Anzali Lagoon and its tributaries reflects the ecological conditions. The presence of Caspiomyzon wagneri, Sabanejewia aurata and Alburnoides bipunctatus in outflows and in the lagoon's tributaries indicates good water quality as these species are known to be less tolerant to heavy loads of toxicants and pollutants. The total absence of Salmo trutta caspius which used to spawn in Pasikhan and Siahdarvishan rivers some 30–40 years ago may be explained by the heavily reduced stocks of this species everywhere in the Caspian Sea, as well as by the presence of weirs and dams built on all inflowing rivers, preventing this species its access to the upstream spawning grounds. The same is probably true for Barbus brachycephalus. This cyprinid was abundant in the Anzali Lagoon, and in 1969/70 and 1970/71 fishing seasons its mean annual catch in the Bandar Anzali region was 33 and 55 t respectively (Appendix 11). At present only a few fish are captured. Barbus brachycephalus now seems to have been replaced by its close relative Barbus capito. However, the latter is much smaller than the former (maximum weight 14.5 kg and 3.5 kg respectively) and never occurs in commercially significant quanties. More data on species not recorded during project investigations may be found in Appendix 11 and on those which were not known before in Appendix 12.
2.3.5.1 Basic infrastructure
Until 1963 there was a commercial fishery in the Anzali Lagoon and 30–40 haul seines, each 400–600 m in length, were regularly operated there. However, due to the continuous shrinkage of the lagoon's open-water area and rapidly decreasing fish catch, commercial fishing stopped after 1964. Some fishing continued and at present there are both licensed fishermen and poachers. The present number of licences issued is 832. Licences are issued for six sectors of the lagoon and are valid for one year. However, this is a mere formality. Licences are free of charge and fishermen are not requested to declare their catch. Apart from licensed fishermen there is an unknown number of poachers. There are no permanent fish landing sites on the lagoon and there is no control over the fish catch. The fishing season officially commences on 13 October and ends on 5 April. However, the fishing season is adhered to only by fishermen using haul seines. Although gillnets are officially prohibited, they are the most common fishing gear used in the western basin of the lagoon. Other fishing gear in use are cast nets, scoop nets, haul seines and rod-and-line. Most fishing is done in the western basin, in outlets and inflowing rivers, while the eastern and southern basins are less frequently fished, only where open water is available and in the lower courses of channels. There is no size limit and fish of all sizes are consumed by fishermen's families or sold in the market.
2.3.5.2 Fishing effort
There are about 1 200 persons fishing in Anzali Lagoon. Taking into account this number and the area of the open water (58 km2) accessible for fishing in 1989, the density of fishermen is 20.69 fishermen/km2. This is a very high fishing effort. However, it is suspected that the fishermen's density in the Anzali Lagoon is substantially higher, especially during the spring and autumn migrations of some fish species. It is therefore recommended to use seasonally an aerial photography for counting the number of persons fishing in the Anzali Lagoon.
The total number of boats which are plank-made, dugout canoe and also plastic fibre vessels with outboard motor, is not known. According to the census done between December 1990 and November 1991 the average number of boats counted daily was 24, i.e., 0.41 boat.km-2. The number of haul seines, which are up to 300 m long and operated daily between December and April, varied from 1 to 17 (average 7.27) and the number of cast nets counted daily during the whole year fluctuated from 2 to 18 (average 6.68). However, the latter figure is certainly an underestimate. The total length of gillnets operating in the western basin is not known. However, it must be very high as the national project staff carrying out the census was able to check up to 11 400 m some days, and the average length of gillnets checked was 2 593 m. day-1.
There are no exact data on past fishing effort in this Lagoon except for a short note by Vladykov (1964) who writes that in the 1930s, when the Lagoon was 4–8 m deep, from 30 to 40 seines, 450 m in length, more regularly operated there. However, the most important fishing gear seemed to be the gillnets, as Il'in (1927) clearly writes (p. 106) that “The only commonly used fishing gear is the gillnet called “dam” or “dom”. They were densely set in front of the harbour and in the channels between the islands. Their number is unknown, but must be high as …this entire area, excluding sites separated by floats and specified for the port and the passage of ships, is filled with rows of gillnets. During the kutum migration, January-April, many gillnets are set in the middle of this bay”.
2.3.5.3 The fish catch
The data on the fish catch given below and in Table 23 were collected during the project. There are no fish catch statistics available after 1964. The data from the present survey should be considered as being probably lower than the actual catch as they represent only those fish counted by the national project staff since January 1990 until November 1991. It is likely that the annual fish catch in the Anzali Lagoon is around 100 t, and so the yield is about 17 kg.ha-2. Taking into account data by the Hydrorybproject (Table 24) on the catches from 1932 to 1964 and for the open-water area corresponding to individual years (Fig.3) the mean annual catch for 1932–35, 1952–56 and 1962–64 is about 218, 105 and 19 kg.ha-1 respectively. At the same time, the fish catch composition also displays dramatic changes. As seen in Table 24, the fishery in Anzali Lagoon has been based almost exclusively on migratory species which formed 98–100% of the total fish catch, and the resident fish such as Esox lucius, Silurus glanis and the non-migratory stocks of Rutilus rutilus, Cyprinus carpio and Abramis brama, reported to occur in the lagoon in small numbers. At present, however, the migratory species declined to 6.6 or at most 15.7 % of the total catch*). Table 23 shows that 62% of the total catch is represented by Carassius auratus, which was accidentally introduced with Chinese carps. Abramis brama and Stizostedion lucioperca which represented an important part of the total catch till the end of the 1940s virtually disappeared from the lagoon, as only single specimens of both were recorded in the fishermen's catch. Almost 10% of the total catch is represented by introduced Chinese carps which do not reproduce in the Lagoon and are regularly stocked. However, considering the number of grass carp, silver carp and bighead carp caught in 1990–91, 315, 6 585 and 466 specimens respectively, and the number of juveniles stocked each year (Appendix 12) the respective yield to the fishery of these three species is only 0.03, 2.61 and 0.68%.
Certainly the dramatic decline of the catch and the change of its structure are closely related to the deep alteration of the Lagoon environment caused by the rapid retreat of the Caspian Sea from 1929 to 1977. A decrease of the open-water area, siltation and subsequent growth of submerged and floating macrophytes, along with damming of inflowing rivers, induced substantial reduction of spawning grounds of anadromous fish species. Aquatic macrophyte production, accelerated by increased nutrient input, inhibited phytoplankton growth which in turn resulted in the decline of the zooplankton and zoobenthos concentrations and worsened the fish food resources. This together with the increasing oxygen deficiency had a negative impact upon the survival of fish larvae and juveniles. Gradual alteration of the formerly brackishwater lagoon into the freshwater marsh favoured the Carassius auratus population which eventually replaced the native anadromous but also resident fish species. The lack of any fishery regulations and increasing poaching also significantly contributed to the low fishery value of the Lagoon.
2.3.5.4 Fish stock assessment
The stock assessment of individual fish species is based on samples taken from fishermen. The fish could not be weighed for lack of balances. Some samples still await processing. Thus the stock evaluation is based mostly on the growth in length assessment. More attention was devoted to Rutilus frisii kutum as this fish represents the basis of the Iranian fisheries in the Caspian Sea and its role in Anzali Lagoon will further increase with the gradual recovery of this waterbody.
Carassius auratus is the most abundant fish in the Lagoon, the catch of which in 1990–91 exceeded 42 t (Table 23). Samples collected from various parts of the Lagoon showed that its maximum age is 6 years. In other geographical areas, however, 9–10 year old specimens were found (Dryagin, 1949; Nikol'skii, 1956; Serov, 1959). The low age of this species in the Lagoon is certainly due to very high fishing pressure. The population is represented by females only. It is not known the males of which species participate in the reproduction of C.auratus. There are probably the resident ones among which Cyprinus carpio, Tinca tinca, Abramis bjoerkna and Scardinius erythrophthalmus may be considered in this respect. Its growth in length (Table 26) in particular age groups is regular indicating the low variation of environmental conditions during the past few years. In comparison with available data from other localities its growth rate is among the most rapid (Table 27), suggesting a favourable feeding condition and no overpopulation. This species, although predominantly a zooplankton-feeder, is an omnivorous fish feeding on a wide variety of food, including phytoplankton, filamentous algae, zooplankton, zoobenthos, macrophytes, detritus and even juvenile fish (e.g., Ereshchenko, 1959; Zhukov, 1965; Penyaz et al., 1973; Kukuradze and Mariyash, 1975). It can easily switch from one kind of food to another, according to what is available. The growth characteristics Clh shows the decline of the growth rate after attaining the second year of life indicating thus sexual maturation. However, dissection of some specimens 90–110 mm in SL at age 1 and 1 + revealed ripe sexual products suggesting that the first spawning may take place even at age of one year. This, together with the high fecundity of this species, polycyclic ripening of sexual products and intermittent spawning, and other unique properties of this species (Holčík, 1980) significantly contributed to the dominance of this species in the Anzali Lagoon.
In the Caspian Sea Cyprinus carpio occurs in two ecological forms: one is indigenous dwelling in freshwater and the second is diadromous (or semi-diadromous in Russian terminology) inhabiting the brackishwaters not far from the river mouths and entering the freshwaters only for spawning (Berg, 1948, 1949; Nikol'skii, 1949; Shikhshabekov, 1969; Kazancheev, 1981; Kuliyev and Ustarbekov, 1982; Kuliyev and Agayarova, 1984). They differ in colour and growth rate - the former is dark and slow-growing while the second is yellowish and grows quickly. Both forms exist in Anzali Lagoon. The first is less numerous, and the scarce data available refer to the diadromous carp. First specimens start to appear in rogas at the beginning of January, then their number increases and maximum migration occurs in May when the highest number was taken also in the western basin. Sample analysis showed that the stock is composed of seven age groups. According to information from the Azerbaijan and Dagestan coast of the Caspian Sea, the sexual maturity of carp is attained in the fourth, third, and even in the second year of life, and the same is probably valid also for the Anzali Lagoon carp, as 51% of the samples analysed includes the two (20.9%) and three (30.2%) year-old specimens. Moreover, the growth characteristics (Clh) which are very high after attaining the second year of life, show significant decline between the third and fourth years of life indicating that sexual maturity has been reached. After the third year the percentage of the catch drops considerably, being 13.9, 11.6, 9.3 and 7% in age groups 4, 5, 6 and 7 respectively. It is interesting that at the beginning of the 1970s RaLonde and Walczak (1970, 1971) found the same age composition not only in the Anzali region but also in other areas up to the Babol River. They also discovered almost the same decline of older carps and the low recruitment as now observed by the authors who agree with RaLonde and Walczak (1970, 1971) that these phenomena are closely connected with the high fishing pressure on carp and the unfavourable spawning conditions in the Anzali Lagoon. Concerning growth only the general average is available from 127 specimens sampled (back calculation growth in length, Rosa Lee method, correction factor 22 mm):
Age (years)
1 2 3 4 5 6 7
SL (mm) 138 203 271 338 400 460 517
Clh 53.3 58.6 59.9 56.9 59.9 53.7
According to these figures the Anzali Lagoon carp is among the fast-growing populations of this species characteristic for the Southern Caspian. However, its growth seems to be slower (Table 28) in comparison with carps from the same area. Direct comparison with the growth in 1969–71 is not possible as RaLonde and Walczak (1970, 1971) used direct measurements: they measured fork length and instead of numerical data they only plotted the graph. The present catch of Anzali Lagoon carp (6.9 t, or 9.1 %) is much lower than before the 1940s when it reached values of 500–600 t. It is the result of the decline of the Caspian Sea level, the lost of spawning grounds, but also the heavy fishing pressure drawing off many juvenile fish.
Rutilus frisii kutum. This cyprinoid fish is highly appreciated by lranians and it is the second most prized fish after Salmo trutta caspius, which is, however, not available to the general public because of its very high price. According to available statistics (Table 29), the catch of kutum in Iranian waters rose from 1 500 t in 1987 to almost 9 000 t in 1991. If these statistics are reliable (the catch of fish in Iran is seldom weighed or counted and the amount of fish caught is estimated only), the present catch is even higher than it was in the mid-1930s when the maximum catch of kutum reached 6 000 t (Emadi, 1979). The catch of kutum overcame the serious decline since that time and according to Emadi (1979) it dropped to slightly over 100 t in the early 1960s. It was mainly the intensive artificial breeding of kutum since 1974 and stocking of larvae and then fingerlings into lower courses of some rivers entering the Caspian Sea which stopped the decline and then increased the catch of this species. According to data from the Fisheries Research Centre in Bandar Anzali, the number of fingerlings released has grown from 38 million in 1986 to 170 million in 1991 (Table 30). About a quarter of this amount is released into the watershed of Anzali Lagoon, especially in its outlets.
Various sources indicate that the centre of the kutum fishery was Bandar Anzali area (II'in, 1927; Berg, 1948–1949; Kozhin, 1956;Emadi, 1979), where up to 98% of the total catch of kutum in Iran has been taken. Its population density must have been very high. II'in writes that in February 1914, 41 000 kutum were caught in the Anzali area. In other place he writes that in the mouth of the Anzali Lagoon (= harbour) the masses of upstream migrating kutum were so dense that people used buckets to catch them, and the jumping fish frequently fell into the boats. The mean weight of migrating spawners was around 5 Russian pounds, i.e., about 2.05 kg. The migration began in February and lasted three months. That was the main migration, but there also existed a second, much weaker run, which was observed in the autumn (Derzhavin, 1934; Razavi, pers.comm.).
Although no exact data are available, reports of fishermen also indicate that these two spawning migrations into the Anzali Lagoon still exist. The first run, which is far more numerous, appears at the beginning of February and it lasts until the end of April. Water temperature varies from 8° to 10°C. The second run, which is very weak in comparison with the first, takes place in late autumn and winter (November-December). If the catch records of the fishermen during the year represent the actual situation, then only about 1% of kutum enters the lagoon in autumn, and 99% in spring. This, however, remains to be investigated. Available observations indicate that there are differences in spawning substrata used by both forms to lay their eggs. It seems that females of the autumn population, which spends winter in the lagoon or its tributaries, attach their eggs to roots and floating fragments of bullrush and also to submerged vegetation and freshly flooded riparian plants, provided that there is sufficient water exchange and a good transparency of water. The spring population fish spawn in the foothill zone of rivers, where eggs are laid on clean gravelly or sandy bottom (Abdurakhmanov, 1962, Shikhshabekov 1979, Magomedov et al., 1987; Belyaeva et al., 1987). II'in (1927) and also Ghanbari (pers.comm.) observed that at the beginning of this century and in the mid-1940s respectively, the Anzali Lagoon was the spawning ground of kutum. Spawning took place along the shores and among reeds. “During this time the reeds rustle as if of wind as the fish rubbs pushing their flanks to the reed stalks or pushing forward among reeds standing in rows” (Il'in 1927, p. 106). At present, however, for spawning purposes, kutum completely avoid all three basins of the Anzali Lagoon, which are either overgrown by reeds (Seyjan and Shiakishim), or have a muddy bottom covered by submerged vegetation.
It is said that the juveniles, after hatching and absorbing the yolk sac, immediately begin to migrate downstream and enter the sea. However, observations during the project indicated that the young-of-the-year stay in the freshwater or brackishwater of the lower course or mouth of rivers for one or two years and only then enter the sea (Holčík, 1992). Analysis of scales of kutum, taken from both juvenile and adult specimens, revealed the existence of the larval annulus or juvenile mark known from other species of fish, the characteristics of which fully agree with the description of this type of annulus by Chugunova (1959). Presence of the juvenile mark was detected in most young-of-the-yearlings, and in 53% of the older and larger specimens. Moreover, juvenile kutum age 1 year were collected in inflowing rivers, outflows and near outflows from the lagoon in April. This is clear evidence that the young kutum enters the sea only 1–2 years after hatching. Those fish which spent the first year of life in freshwater grow more quickly than those entering the sea only after 2 years (Tables 31, 33, 34, 35) and, consequently their population structure is also different (Table 32).
The presence of juvenile marks on the scales of this species has been detected also by RaLonde and Razavi (1972) but they gave no further information nor analysed this phenomenon. It is not known if also the stock in Azerbaijan or Dagestan displays juvenile mark on its scales.
Spawning shoals are composed of 3 to 8-year-old fish; the prevailing age group being 4 and 5 in males and 5 and 6 in females. This differs from the data of RaLonde and Razavi (1972) who reported the predominance of age-groups 3 and 4. Moreover, in the authors' samples the 2-year-old fish did not occur, while in their sample from 1969–70 this age-group has been represented by 10.9% (see also RaLonde and Walczak, 1970, 1971). This indicates eldering of the kutum stock in comparison with that of twenty years ago, and suggests lower fishing effort.
This species reaches sexual maturity at 3 years in males and 4 years in females (Abdurakhmanov, 1962; RaLonde and Walczak, 1970, 1971). In recent years, however, sexual maturity and first spawning have been one year earlier in both sexes (Razavi, pers.comm.). The growth characteristics (see below) confirm this: males mature sexually at age 2 and females at age 4 years; however, the mass of spawners is aged 3 and 4 years respectively.
The growth of this species in recent years (Tables 34, 35) in Anzali Lagoon is considerably slower than 20 years ago, also when compared with other localities from the southern Caspian (Table 36). But the population density of the Rutilus frisii kutum is high and there is therefore a high competition for the food resources. Until about third year of life males grow faster, but afterwards more slowly than the females. Their lifespan is shorter and the maximum length less than in females (Tables 32–37).
There are differences between fishes which enter sea after attaining their first year of life and those which have spent two years in freshwater (Tables 32–37). The former sexually mature earlier, their growth rate is faster and lifespan shorter than the latter. However, more studies are needed to further understand the biology of both groups and to determine if they need separate fishery management.
Chalcalburnus chalcoides or shemaya from the southern Caspian is considered a subspecies iranicus (Svetovidov, 1945). Abdurakhmanov (1955) considers it to be identical with the subspecies longissimus described by Varpakhovskii (1892). The difference between the two, however, are mostly by way of some plastic and one meristic characters. However, it is known (e.g., Derzhavin 1934; Kazancheev, 1981) that the Caspian shemaya is not represented by one form only and that different regions are inhabited by different subpopulations.
Shemaya is an important and appreciated diadromous fish both in Iran and along the western coast of the Caspian Sea. According to reports of local fishermen, confirmed also by Razavi (pers.comm.), its catches (for which there are no statistics in Iran) were more numerous in the past than today. This is confirmed by Abdurakhmanov (1953) concerning the catch of shemaya in Azerbaidjan. No doubt the decline is due to the damming of rivers, the principal spawning grounds of this species.
Two runs of migrants were recorded in the Lagoon. Spawning run enters the Lagoon in spring (late February-early April) and is caught by cast nets in inlets and outlets, while the feeding run occurs in summer and autumn (July-September) and is taken mostly by gillnets and in the western basin only. This was also observed in the past in the Anzali Lagoon by Derzhavin (1934). The spring spawning run is more numerous than the autumn run. The range of migrants varies from 105 to 290 mm in SL, mostly between 130 and 170 mm, and the average SL was 140 mm. The spring run, from which data are available, is composed of fishes 2–5 years old. The most numerous (63%) is the age group III. This agrees well with data from the Kura River (Abdurakhmanov, 1953, 1962). Spawning of this species is reported to be in streams only, over clear gravelly bottoms and lasts from June till end September (Abdurakhmanov, 1953) but it remains to be investigated if it is valid also for Anzali Lagoon. The growth in length of this species in the Lagoon (Table 38) may be classified as average (Table 39) compared with that of other populations from the southern or southwestern Caspian. According to the growth characteristics Clh growth rate during first three years of life is high and then declines, suggesting that sexual maturity has been reached. This is in agreement with the findings of Abdurakhmanov (1953) that the males and females of shemaya entering the Kura river for spawning are sexually mature at age 2–4 and 3–5 years respectively.
Vimba vimba persa is not included in the Iranian statistics. However, it may be considered an important diadromous (Abdurakhmanov, 1962) or semi-diadromous (Berg, 1948–1949) species. Catches along the Azerbaijan coast in 1934 reached 67 t and on the Dagestan coast almost 132 tons in 1937. The species is frequently seen in the fish market of Bandar Anzali, and according to the authors' census in 1990–91 the catch of local fishermen in the Anzali Lagoon was 823 kg or almost 8 400 specimens.
The first fish started to enter the Anzali Lagoon in mid-January at a water temperature of 8°–9°C. With increasing temperature the number of fish progressively rises, with a peak from 21 April until 10 May, when the total number counted in traps reached 63.5%. At that time the water temperature was 19°–21 °C. Then the number of migrants considerably declined and at the end of May only single specimens were caught. The size of migrants varied between 170 and 250 mm. The average standard length of 1 568 specimens measured was 162.4 mm and the average weight 85.1 g+). All fish caught belonged to age groups III–IV and all were sexually ripe. The overwhelming majority is composed of age groups III and IV the share of which is 34.3 and 50% of the total respectively. This indicates that the first spawning fish form most of the population. The number of eggs ranged from 7 566 and 29 050, the mean number per female of 180 mm SL is 17 245 eggs. The number of eggs increases with increasing size of female (F = -38903.9926 + 311.9385 SL, where F = fecundity, SL = standard length in mm). The length-weight relationship of both sexes is w = 0.0000034 SL3.3469, where w = weight in g and SL = standard length in mm. Comparing these data with those of Abdurakhmanov (1962) and Shikhshabekov (1979) for the V. vimba populations from the Azerbaijan and Dagestan coasts of the Caspian Sea, considerable agreement can be seen in most of the data, especially concerning the water temperature during migration, age composition of migrants and also the share of particular age groups. The difference is that the Vimba females from the Anzali Lagoon produce a lower number of eggs per female of the same size: Abdurakhmanov (1962) found 25 200 eggs as average number for females of SL = 171–190 mm. The authors' data, however, come from a rather small sample of only 16 specimens. Eggs are laid onto a clear, sandy, gravelly or stony bottom of streams. In the absence of such substrate it uses concrete structures, and also the freshly inundated meadow vegetation provided that there is some current. Individuals not able to overcome obstacles such as weirs mass in front of them, do not spawn and their milt and eggs resorb (Shikhshabekov, 1979). Vimba migrating into the Anzali Lagoon (Table 40) has an average growth rate similar to that of other Vimba populations from the southwestern and southern parts of the Caspian Sea.
In summary, the present Anzali Lagoon has a fish community composed mostly of the resident fish species, and dominated by Carassius auratus. The migratory species which formed a backbone of the Anzali Lagoon fishery some 4–5 decades ago are in the minority. First spawning specimens dominate which is the result of stocking. The rather low growth rate of migratory species is probably owing to a comparably low fishing intensity as found by Strubalina and Chernyavskii (1992) on examination of migratory Rutilus rutilus in the Caspian Sea. Competition for food seems unlikely as the area of feeding grounds is concurrently increasing as a result of the rising level of the Caspian Sea.
+ Fish taken in traps were examined in the laboratory and in this case they were also weighed.
2.3.5.5 Crayfish stock assessment
The crayfish population in Anzali Lagoon is represented by Astacus leptodactylus and not by Astacus pachypus as stated by Vladykov (1964). The latter occurs only along the coast of the Caspian Sea, on clean, unsilted, gravelly or stony bottoms, and such conditions do not presently prevail in the Anzali Laogon. However, it is likely that 40–50 years ago, when the Lagoon was a brackish waterbody with sandy and gravelly bottom, it was inhabited by the latter and not the former species, and that Vladykov's identifiation of A. pachypus was correct.
In 1988 SHILAT issued a license to a Turkish company to harvest crayfish in Anzali Lagoon. Almost 13 t of crayfish were caught that year and exported alive to Turkey. However, as the fishery for crayfish had not been preceded or paralleled by any research, it was felt that further harvesting would lead to stock depletion, so the contract was revoked and crayfish fishing halted until the ecology of this animal in the Lagoon is clarified.
Investigations on crayfish biology were carried out by the National Project Staff, especially by M. Karimpour, in seven stations in the Seyjan and Siahdarvishan canals, the lower course of the Bahambar River and in the Siahdarvishan and Kolesar Rivers. Research focused on crayfish habitat characteristics, impact of environmental conditions on its behaviour, reproductive biology, population parameters such as abundance and mortality, and data and evaluation of potential yield.
Sampling of crayfish was performed using baited cylindrical traps with entrance funnels on both sides. Traps were arranged in line formation. The length of one set of traps was 50 m, the diameter of the entrance funnels was 42 cm and mesh size 18 mm. The set was checked daily, usually early morning. The crayfish caught were measured with calipers to the nearest millimetre. Total length (TL), carapace length (CL) and orbital carapace length (OCL) were measured, but only OCL is considered in this report *). Crayfish were then marked by punching of their tail and released. Fecundity was also investigated using 43 females taken at random. Samples from the Siahdarvishan, Bahambar and Kolesar Rivers and those taken in the canals of the eastern region of the Anzali Lagoon were put together and treated as the Siahdarvishan and Seyjan region respectively.
The following information is based on the report by M. Karimpour, N. Hosseinpur and D. Haghighi “Preliminary investigation of Anzali Lagoon crayfish Astacus leptodactylus”.
Habitat: Anzali Lagoon crayfish occurs predominantly in the lower courses of the inflowing rivers. It is distributed along the banks at depths not exceeding 3 m. Preferred habitats are overhung banks, bottom depressions and places overgrown by macrophytes (Myriophyllum, Typha, Scirpus), provided that the habitat, which offers both forage and shelter, has running water.
A. leptodactylus also occurs in the Caspian Sea where it is occasionally caught by fishermen in gillnets up to 60 m depth.
Movements and activity: The releasing of crayfish at a certain distance from the place where they were taken and marked revealed that it is a territorial animal with a clearly demonstrated homing instinct. The percentage of animals which returned to the place where they were caught was 60, 8 and 0 for those released at 100–200, 300 and 400 m respectively. These results suggest that there is no or little mixing of crayfish populations from neighbouring rivers and that the Anzali Lagoon population is composed of individual sub-populations or unit stocks which differ among themselves also in some biological parameters, as will be discussed later.
Activity of crayfish is governed mainly by water temperature. It was found that their activity demonstrated by the daily catch rate decreases considerably when water temperature rose to 26°C. Further rise in temperature is accompanied by increasing mortality which amounts to 60% at 32°C, especially in shallow habitats. The high water temperature occurs in summer, especially in June and July, and coincides with the lower discharge of rivers and high water transparency.
Size and length frequency: The largest crayfish caught in the Siahdarvishan and Seyjan regions measured 145 and 138 mm TL respectively, i.e., 54 and 49 mm of the OCL. Differences between the two stocks were also found in mean size and length frequencies. The Siahdarvishan stock OCL mean size was 36.6 mm but that in the Seyjan only 33.0 mm, and the difference is statistically significant (t = 12.82, P<0.001). While the mode OCL length in both stocks is similar, being 34.6% in the former and 49.3% in the latter in size group 30–34 mm, the frequency of other size groups is different. In the Siahdarvishan stock the frequency of size groups 35–39, 40–44, 45–49 and 50–54 mm OCL is 28, 21.8, 7.4 and 0.8% respectively, but these frequencies in the Seyjan stock were 22.7, 6.7, 1.7 and 0 (Table 42). This indicates that the crayfish stock in the Siahdarvishan region is composed of more age groups and the lifespan is higher than in the Seyjan region, where there is a sudden drop in abundance of the larger (and older) crayfish. A plausible and possible explanation is that environmental conditions in the Seyjan region are not favourable for the crayfish and this is also indicated by the unfavourable oxygen content in this region (see section 3.3.1, Appendix 3, Figure 9).
Mortality: Table 42 also shows the survival and mortality rate of the crayfish stocks in the Siahdarvishan and Seyjan region respectively. As can be seen, the values of these parameters are in contrast, as in the Siahdarvishan region the survival rate is twice as high and the mortality twice as low than in the corresponding data for the Seyjan region. The figures represent natural mortality rate as there was no fishing for crayfish during the sampling period.
Reproductive biology: Since mid-December the first females bearing pleopodal eggs were observed in all sampled habitats of Anzali Lagoon. The minimum size of females with eggs was 25 mm OCL, or 81 mm TL. At that time the water temperature ranged from 9 to 11°C. In combined samples the absolute fecundity of females 25–45 mm OCL varied from 92 to 412. There is a positive correlation between female size and number of eggs and the respective GM regression of that relationship is:
| where | F -398.9679 + 18.9161 OCL |
| F = number of eggs and OCL = OCL length in mm. |
The first young crayfish were observed during the first ten days of March and the last group of females bearing juveniles were recorded in the first ten days of May. This indicated that the reproductive period from the beginning of mating till the release of juveniles lasts about 6 months.
Moulting: There are two moulting periods in the Anzali Lagoon crayfish population. The first moulting occurs at the beginning of April when the water temperature reaches 12°C. Males moult before females which start to moult almost three weeks later when some of them have already released the juveniles. The peak of male moulting was observed during the second ten days of April, when 80% of males had already moulted. The water temperature then ranged from 17 to 18°C. At the end of April the moulting of males is completed. In females the moulting lasted until end-May. The second moulting period was observed in September after the end of the high water temperatures. The second moulting is synchronous in males and females.
Investigations carried out during this project have shown that at present the Anzali Lagoon has a low fishery importance. In spite of high fishing effort, the fish yield is low, and coarse fish dominate as the commercially valuable species are severely depleted. This is due to the profound environmental changes in this ecosystem over the past 50–60 years as a result of the Caspian Sea level decline. Man-induced changes such as the damming of the inflowing rivers, accidental introduction of the German carp (Carassius auratus) and absence of fishery management have also contributed to this situation. Extraction of water for irrigation, eutrophication and to some extent also pollution are further constraints placed on the ecosystem and contribute to environmental changes. Since 1977 the rise in level of the Caspian Sea has started to lead to a slow improvement of the situation. The Anzali Lagoon is gradually returning to its former brackishwater status. However, although the Caspian Sea level is now even higher than the long-term calculated level for 1879– 1930, the environmental conditions of the Lagoon are far from those which it had around 1930. Its full environmental rehabilitation, fundamental for both recovery of the fisheries and wildlife diversity, will require considerable effort including hydraulic engineering measures, an antipollution strategy and wise fishery management.
