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This study is attempted to compare the number of rings and circular scales that are formed during various ages on Liza saliens. Sampling was carried out monthly during 2012-2013 using beach seine fishing nets. 102 specimens of different sizes were collected and transferred to the laboratory in boxes containing ice. The age of fish was determined by the number of annual rings as well as, the number of rings in each annual area. The distance between rings in each annual area was also measured. The results showed that the maximum growth was demonstrated in the first and second years. In the first year of life, the scale radius was nearly 2823.3±366.5(µm) which decreased to 1223.9±236.0(µm). The result indicated that 48 percentage of growth scales occurred in the first year and this value is only 21.8% in the second year. The number of growth rings in the annual regions decreased with increase in age. The result demonstrated that the average number of rings was 95.5±17.6 in the first life year of the fish. If you take into account the number of growth ring through years in comparison with the number of days in a year, it is clear that one ring was nearly made in four days in the first life year and it gradually reached 7.5, 15.9, 21.9 and 31.7 in the second, fourth and sixth years of life, respectively. One ring was approximately made in each month at higher ages.

The main objectives of the present study were to estimate of biomass during 1997-2014 and maximum sustainable yield of common kilka Clupeonella cultriventris Borodin, 1904 in 2013 in Iranian waters of the Caspian Sea. This paper examines the maximum sustainable yield (MSY) and fishing intensity at MSY (fMSY) and then using fMSY, yield-per-recruit and spawning biomass-per-recruit under various harvest strategies of Fmax, F0.1 and F40%; the acceptable biological catch (ABC) was estimated. During 1997-2014, the biomass of common kilka was increased from 22000 in 1997 to 112000 t in 2009 then declined to 83300 in 2013. In the period, the instantaneous coefficient of fishing mortality varied between 0.246/yr to 1.640/yr and the exploration rates were 0.327 and 0.764. The reference points of common kilka at F0.1 and F40% were estimated 0.92 and 0.80 year−1 , respectively. According to Schafer model the MSY and fMSY were estimated 22670 t and 8690 vessel×nights (a unit of effort). During 2013, the ABC of common kilka was estimated 17500, 20060, 23500 and 18900 t in tiers 2, 3, 4 and 5, respectively. However, for the implementation of a precautionary management approach the lower and more accurate ABC-value, based on more information, should be selected and thus the catch should be restricted to 17500 t.

A mass-balance Ecopath model of coastal areas in the Caspian Sea has been constructed for a quantitative description of the trophic structure of the ecosystem. The model is used to estimate the important biological parameters and relationships among the different ecologically important groups. Twenty five species were used in the present analysis. The model is based on the data collected of Kilka fisheries, beach seining (Bony fish fisheries), and set Gillnet (Sturgeon Fisheries) and also dietary information. Total landings along the Iranian portion of southern Caspian coast reached 39647 t, including sturgeon (41 t), kilka (22873 t) and bony fishes (16733 t) in 2014. Two species of kilka (Common kilka and Anchovy) are important commercially in the Caspian Sea, together accounting in the past decade for > 60 % of the total catch, as well as being a crucial part of the food chain. The mean average trophic level was estimated at 3.17 by Ecopath software. In this research, the mean level were studied between eight species varied from 2.56 to 4.04, Sander lucioperca occupy the highest and the as vimba vimba was the lowest level. The ranges of total mortality varied from 0.5 to 2.56 per years. The food consumption rate was estimated about 101.56 per year Mixd trophic level index (MTI) showed small pelagic fishes as prey, have crucial role in feeding of pelagic predators population such as invasion of the ctenophore Mnemiopsis leidyi, bream fish and benthic fish such as sturgeon. In general, niche overlap was greater in more species such as Alburnus chalcoides, Rutilus rutilus, Clupeonella cultriventris, Rutilus kutum and M. leidyi who consumed large amounts of plankton. In conclusion small pelagic fish exert a major control on the trophic dynamics of the Caspian Sea ecosystems and constitute midtrophic-level populations.

This study was conducted to determine growth parameters, catch and fishing effort trends, stock assessment and Acceptable Biological Catch (ABC) of Caspian Sea mullets in the Iranian coastal waters of Caspian Sea in the fishing season of 2012-2013. For gathering of data on biometry and catch statistics, 5 mobile working group in the regions of Anzali, Kiashahr, Nowshahr, Babolsar and Torkmen were involved from the start to the end of fishing season.Gathered data Were entered to the computer. For data analysis, common methods were undertaken for estimation of growth parameters, mortality rates, biomass and Maximum Sustainable yield (MSY) and Acceptable Biological Catch (ABC) as well. According to the result, the number of beach seines cooperatives was 124 and fishing efforts were 45260 beach seining haul. The catch per unit of effort CPUE) was calculated 37 kg/haul during this fishing season. The total catches of Caspian Sea mullets (including illegal fishing estimated as 2151 mt. Growth parameters of golden gray mullet (Liza aurata) were estimated as K=0.12 /yr, L_∞=59.24 cm, t_0 = - 1.31 /yr. Based on catch-at-age data, in the fishing season of 2012-2013 , the total biomass, from the biomass-based cohort analysis were estimated 11321.6 mt. The reference points of F0.1 and F30% were estimated 0.3 /yr . based on these results , the fishing mortality rate in fishing season of 20122013 were very closed to these reference points. In this survey , the Maximum sustainable yield and Acceptable biological catch were estimated as 2207.7 and 1981.4 mt respectively .Results of biometry of leaping gray mullet (Liza saliens) showed that the mean length and weight of this species were 28.8 ± 3.4 cm and 230.5±74.8 g respectively. Based on these results and due to decline of golden gray mullet stocks, it is recommanded to reduce fishing effort and harvest keep to the level of MSY and ABC .The study of spawing condition of golden gray mullet in new situation of this species is also recommanded.

Environmental pollution by heavy metals has been a matter of growing concern over the last decades. Heavy metals are toxic and tend to accumulate in living organisms. In many studies, fish has been used as a sampling item to monitor the quality of ecosystems because of two reasons: 1- Fish bio-concentrate and integrate contaminant load both in time and space leading to more representative results compared to water samples, and 2- Fish represent the bio-available fraction of environmental contaminants, unlike water and sediment samples. On the other hand, humans consume fish species which makes attention to these fauna even more important. Levels of some metals in the water running in Volga River, towards the Caspian Sea, and elevated concentrations of some trace elements have been reported in sediment. Also, various pollutants have accumulated in the Caspian Sea due to effluents from coastal catchments and leakage from offshore oil production and land-based sources. ... The objective of the present study was to investigate the concentrations of chromium (Cr), cadmium (Cd), cobalt (Co) and lead (Pb) in fish muscle in the most commercially important fish species of kilka (common kilka, C. cultriventris, anchovy C. engrauliformis and bigeye kilka C. grimmi) in the Caspian Sea.

The purpose of this study was to investigate the possibility of natural reproduction of indanger fish in the southern Caspian Sea in Tajan, Haraz,Sardabrood and Chalos rivers, and identify suitable habitats for this species in the study area as a genetic reserve.Sampling of physical and chemical parameters of water, macrobenthic invertebrates and fish fauna was conducted seasonaly in each rivers at selected stations from febrary 2010 during one year. Macrobenthic invertebrate sampling were used bySorber sampler and fish was collected by gill net and electroshocker set with a voltage of 1.7 A and 100-300 V. A total of 53 taxa of macrobenticinvertabrateshave been identified in the four mentioned rivers, in which Tajanriverconsisted of 47 taxa with highest richness.20 species of fish were determined in the studied rivers that 6 of them were non-native species.The results showed that the predominant identified fish species were native in the river. The fish species diversity increases as one moves from the headstream towards the estuaries of the two studied Sardabrud and Chalus rivers.The results of this study showed that the relative abundance of fish species resistant to pollution and hard environmental conditions were much more that sensitive species. physicochemical parameters of water such as; water temperature, DO, BOD5, pH, TSS, TDS, EC, turbidity, nutrients, biodiversity index such as Shanon index, EPT, HFBI, EPT/CHIR, nutrition functioning group and present or absent of fish species showed that there are significant decrease in water qualities from upstraem ratio to down stream (For example, in Tajan river water turbidity varied from 0 at station 1 to 333 NTU at station 6, Which is strongly influenced by sand workshops. As well as the activities of a significant impact of fish farming workshop on the Haraz river water quality). The minimum of HFBI index was 2.84 at station 1 and the maximum was recorded at station 5 with 6.01, and there is not any possibility to natural reproduction of migrated species that are dominant and indanger at downstream. Conditions for natural reproduction of this species in the rivers of srdabrood and Chalus there is to some. In Shahid- Rajaei dam the maximum relative abundance of fish species belonged to Capoeta capoeta, Luciobarbus capito and Squalius cephalus, respectively. These species have different age, length and weight stuctures at Shahid- Rajaei dam inhabitant, and the resourval of this dam and it,s upstream have been preparing auch a favorabile condition that seems there are potentioal of introductionand inhabitant of some of the Migratory and indanger fish species such as Barbels, Sturgeon, Alburnus chalcoides and etc. as genetic reserve for biodiversity preservation.

This study was conducted to determine growth parameters, catch and fishing effort trends, stock assessment and Acceptable Biological Catch (ABC) of bony fishes in the Iranian coastal waters of Caspian Sea in the years 2013-2014 and 2014-2015. According to the result, the numbers of beach seines were 124 and 120 and their fishing efforts were observed 44688 and 46299 beach seining, respectively. The total catches (including illegal fishing) were also obtained 17144.3 mt and 16733.2 mt during 2013-2014 and 2014-2015, respectively. The highest proportion of catch was belonged to kutum and golden grey mullet (94.4% and 89.5%, respectively) in two fishing seasons mentioned above. Growth parameters of kutum were estimated as K=0.19/yr, L_∞ =61.3 cm, t0=-0.99/yr. The Growth parameters were K=0.18/yr, L_∞= 61.1 cm, t0= -0.14/yr for golden gray mullet and were K=0.14/yr, L_∞= 70.8 cm, t0= 0/yr for common carp. Based on catch-at-age data, in the years 2013-2014 and 2014-2015, the total biomass, from the biomass-based cohort analysis were estimated 46900 mt and 41000 mt for kutum and 11550 mt and 12670 mt for golden grey mullet, respectively. The reference points of F0.1 and F35% were 0.41/yr and 0.34/yr for kutum and 0.36/yr and 0.33/yr for golden grey mullet, respectively. According to catch of species/groups, three main groups can be divided easily. The one–way ANOSIM catch similarity test indicated that coverage rates of different years were homologous and similar, but the coverage rates of different months, regions and periods were not similar. Also, there were significant differences in community composition of fishes in catch of beach seines among three times; three durations; three regions and seasons (in all cases MRPP, p

The main objectives of the present study were to estimate of biomass and maximum sustainable yield of common kilka in Iranian waters of the Caspian Sea. This paper examines the maximum sustainable yield (MSY) and fishing intensity at MSY (fMSY) and then using by fMSY, yield-per-recruit and spawning biomass-per-recruit under various harvest strategies of Fmax, F0.1 and F40%; the acceptable biological catch (ABC) was estimated. The results showed that the catch of three species of kilka were 24080 and 22969 t in 2012-2013 and 2013-2014 in Iranian waters of the Caspian sea, respectively and common kilka predominated with 98.1% and 98.9%, respectively. Growth parameters were estimated as L_∞=141.8 mm, K=0.297 yea^r−1, t_0=−1.048 year^−1. The ages of common kilka comprised 6 age groups, ranged from 1 to 6 years and Age groups 3 and 4 years old had the highest frequency. In the years 2012-2013, the catch of age 1 and age 4 represented the lowest and highest proportion of total catch (133.6 and 9121.6 t). In 2013-2014, followed the catch of age 1 and age 3 had the lowest and highest proportion of total catch (151.9 and 8700.2 t). The instantaneous coefficient of natural mortality was estimated as 0.506 year^−1 and total mortality and the instantaneous coefficient of terminal fishing mortality were 0.894 and 1.40 year^−1 respectively. In the years 2012-2013 and 2013-2014, the biomass of common kilka was estimated 90700 and 83300 t, respectively. Also, the fishing mortality was 0.622 and 0.894 year^−1 and the exploration rates were 0.551 and 0.636. The reference points of common kilka at F0.1 and F40% were estimated 0.92 and 0.80 year^−1, respectively. According to Schafer model the MSY and fMSY were estimated 22670 t and 8690 vessel×nights (a unit of effort). In 2013-2014, the ABC of common kilka was estimated 17500, 20060, 23500 and 18900 t in tiers 2, 3, 4 and 5, respectively. However, for the implementation of a precautionary management approach the lower and more accurate ABC-value, based on more information, should be selected and thus the catch should be restricted to 17500 t.

Dam reservoirs have important rules in aquaculture and fish farming in many countries. In this regard, water samples of Azad Dam reservoir (Sanandaj) were collected at five stations from July 2015 to June 2016. Then, the results of 18 physico-chemical parameters were compared with the aquaculture standards and thresholds. Results showed that thermocline and oxycline was started from June and they vanished in December. Maximum level of thermal and oxygen stratified were registered during August and June, respectively. Mean of the most physico-chemical parameters were significantly different between surface and bottom layers (T-Test, p

Big-scale sand smelt is one of the fishes with high ecological value, which consume by fishes such as sturgeon in the Caspian Sea. In this study, 191 samples of Big-scale sand smelt from southeast coast of the Caspian Sea were collected seasonally from December 2013 to September 2014. In the present study, food items and the relative index of gastrointestinal (RLG), stomach emptiness index (VI) and feeding intensity (IF) were determined. The fork length, weight and age (mean ±SD) were 7.70 ± 1.09 cm, 3.64 ± 1.49 g and 2.00 ± 0.81 year, respectively. This fish with a relative gastrointestinal tract length of 0.46 ± 0.06 (mean ± Standard Deviation) can be considered as a carnivorous fish. The average of empty stomach was 45% showing big-scale sand smelt is a relatively voracious feeder. The average intensity of feeding (mean± Standard Deviation) 535±221.21, as a moderate level for this fish in the region. Gammarus (benthos) and Daphnia (zooplankton) were the favored food for this fish. This study also showed opportunistic hunting activities of this fish.

This survey was conducted from Babolsar to Bandar-e-Torkaman in the southern part of the Caspian Sea. Specimens were collected from commercial catches (Beach seine net, mesh size 5 mm). Sampling was carried out monthly (from Sep. 1993 to Sep. 1994) to evaluate the biological characteristics, including total and fork length, weight, age, gonad weight and sex. The results indicated that the scales and operculum were suitable for determining the age though the operculum gave better results than the scale. Since the first annulus has not appeared on the scale and it is very difficult to distinguish annuli on the scales of old specimens. This study also shows that the maximum growth rate is belong to the age of 3 years. The b value regression between fork length and weight was 2.940. The relation between scale radius and circuli number, and growth were: C = 4.609 R 0.8282, L_(t) = 322.4 [1-exp^(-0.361(t+0.013))]. Sex ratio was 1:3.14 and female dominated. The Gonadosomatic Index (GSI) indicates that the spawning activity occurs on July-August. Males ripen earlier than females. Furthermore the numbers of circuli in different ages and condition factor (k) relation between total length and fork length and between age and weight were obtained.

Caspian Kutum (Rutilus frisii kutum, Kamensky 1901) is among the main commercial species in the Caspian Sea. The present study aimed to determine the spatial and temporal distribution patterns of Kutum in depth ranges of 10 to 100 m by bottom trawl net in Iranian waters of the Caspian Sea during 2008 to 2010. The results showed that the maximum catch and CPUE were 2903 kg and 57.08 kg/0.5 h in winter 2009. The minimum catch and CPUE were 79 kg and 1.41 kg/0.5 h in spring 2010. During the warm seasons (spring and summer) most Kutums occurred in depths less than 20 m. While, during cold seasons they occurred at all depths. The average (±SE) CPUE was 94.0 ± 78.53 kg/0.5 h in depths 20-50 m in autumn and 128.3 ± 77.64 kg/0.5 h in depths >50 m in winter.

The main objective of the present study was qualitative and quantitative assessment of anchovy stock, Clupeonella engrauliformis in Iranian waters of the Caspian Sea during (1995- 2011). Over this period, total catch of anchovy kilka increased from 32000 tonnes in 2005 to 67000 tonnes in 1999 and decreased sharply to 80 tonnes in 2011. In the years 1995-1999, catch per unit effort (CPUE) was fairly constant (2.92-3.52 tonnes/(Vessels×Nights) which fell to 0.01 tonnes/(Vessels×Nights) in 2011. Total biomass and spawning stock biomass (SSB) had the same trend as CPUE. During 1995-1999, total biomass of anchovy kilka ranged between 158500-185900 tonnes which dropped to 2000 tonnes in 2007. The SSB showed a downwardtrend from 105500 tonnes in 1997 to 1950 tonnes in 2007. In age compositions of the catch, age 3+ was the largest age group. From 2001 to 2003, age 2+ predominated. Finally, number of young specimens declined and age 6+ and 7+ groups were predominated in the last years. Present study indicated that the situation of the anchovy kilka is critical. A coordinated international effort is needed to provide implementation of sustainable management and responsible fishing activities in the whole Caspian Sea.

The project of the Study on fishing and resource management of fisheries within Southern Caspian Sea was conducted on the base of an agreement made between fisheries organization (Shilat) and the Iranian fishery research organization (IFRO) signed in 2010. The study has several phases. The final report of the fishery on fishing and resource management of fisheries within Southern Caspian Sea (Gilan, Mazandaran & Golestan provinces) is consisted of several sections such as: 1- The Survey status of biology and catch of Kilka fishes , Bony fishes and Estrogen fishes and also the status of aquatic resource conservation in the Southern part of Caspian Sea 2- Fishing analysis in the Southern part of Caspian Sea 3- Fisheries development Strategies, policies and plans in the Southern part of Caspian Sea In this survey and library-based study, internal and external environmental factors of shilat activities are considered. Using SWOT analysis method, current situation of fisheries is investigated. In this regard, all fisheries activities were divided into four groups, then, the strengths, weaknesses, opportunities and treats of internal and external environment will be analyzed. A considerable number of tables and matrixes were prepared and policies and strategies as seen of final report were carried out.

The project of the Study on fishing and resource management of fisheries within Southern Caspian Sea was conducted on the base of an agreementmade between fisheries organization (Shilat) and the Iranian fishery research organization (IFRO) signed in 2010. The study has several phases. The final report of the fishery on fishing and resource management of fisheries within Southern Caspian Sea (Gilan, Mazandaran & Golestan provinces) is consisted of several sections such as: 1- The Survey status of biology and catch of Kilka fishes , Bony fishes and Estrogen fishes and also the status of aquatic resource conservation in the Southern part of Caspian Sea 2- Fishing analysis in the Southern part of Caspian Sea 3- Fisheries development Strategies, policies and plans in the Southern part of Caspian Sea In this survey and library-based study, internal and external environmental factors of shilat activities are considered. Using SWOT analysis method, current situation of fisheries is investigated. In this regard, all fisheries activities were divided into four groups, then, the strengths, weaknesses, opportunities and treats of internal and external environment will be analyzed. A considerable number of tables and matrixes were prepared and policies and strategies as seen of final report were carried out. Iranian Fisheries Science Research Institute Published

The main objective of the present study was qualitative assessment of Caspian kutum (Rutilus frisii kutum Kamensky 1901) stocks by using indicators of overfishing, condition factor and relative weight in Iranian waters of the Caspian Sea during a long period (1991- 2011). Three fisheries indicators in catch were: 1) percentage of mature fish, with 100% as target; 2) percent of specimens with optimum length, with 100% as target; and 3) percentage of mega-spawners, with 0% as target, and if no upper size limit exists, 30-40% as representative of reasonable stock structure. Over this period, the condition factor and relative weight had a decreasing trend. The range of length with optimum yield was between 40 and 48 cm. The mega-spawner measured as fish a size larger than 48 cm. According to these three indicators, the percentage of mature (fork length>40cm), optimum size and mega-spawners were 62.0, 40.9 and 12.5% in 1991-92 which decreased less than 50, 38.2 and 8%, in the years 1992-2011, respectively. The length structure is a matter of concern. Therefore, for reservation and rebuilt of kutum in the Caspian Sea, the target was to let all (100%) fish spawn at least once, using bigger mesh size in cod end (e.g. 35mm, during whole fishing season). The aim was also to implement a fishing strategy that result no (0%) mega-spawners being caught, and the main catch focus on optimum length.

Reproduction period, spawning peak and sexual maturity in anchovy kilka were investigated during the year 2006 for sustainable yield assessment in Iranian waters of the Caspian Sea. The mean fork length, total weight and age were 118±5.9mm, 11±1.7g and 4.6±1.2 year, respectively. Mean (±SD) absolute fecundity was 12625±5533 ovules. More than 50 percent of the fish specimens matured when their length exceeded 92.5mm. The results showed that reproduction of anchovy kilka occurred in autumn, and spawning occurred throughout the year and especially in winter. The length and age ranges were found to be shortened compared to the past years with many older fish and less younger ones (< 2 years) in the catch which sharply decreased recruitment. This phenomenon is thought to be due to overfishing synchronized with invasion of M. leidyi pushing kilka to spawn in winter, which all cause collapse of anchovy kilka stocks in the Caspian Sea. We postulate that anchovy kilka has adopted the strategy of spawning year round to mitigate the negative effects of overfishing and invasion of M. leidyi.

This paper aimed to investigate the fishery and biological characteristics of anchovy Kilka in Iranian waters of the Caspian Sea from 2005-2007, including length and age structure ,Von Bertalanffy growth parameters, length and age at first capture, condition factor, sex ratio, natural and fishing mortality. The examination of catch data approved that Kilka population in the Caspian Sea have been declined a few years ago following entrance jellyfish Ctenophora Mnemiopsis leidyi. The greatest destruction of anchovy kilka catch was occurred while the catch of anchovy from 4250 tonnes in 2005 reached to 924 tonnes in 2007. The results showed that K value and L∞ calculated 0.375/year, 131.7mm, respectively. The instantaneous coefficient of natural mortality was estimated 0.49/year. The instantaneous coefficient of fishing mortality and total mortality was 0.51/year and 1/year, respectively. The Exploitation rate was calculated as 0.51. The length and age ranges restricted comparison to last decade and sharply decreased recruitment. In the past few years, the main reasons of disintegrates among anchovy Kilka stocks in the Caspian Sea were synchronized overfishing competitive anchovy Kilka with M. leidyi.

In the years 2007-2007, 2008-2009 and 2009-2010 the exploitation of bony fishes resources (by 131 beach seines) started on 12 October but finished on 9 April, 9 April and 13 April, respectively. During these periods the total catch of bony fishes were 23537.8, 20045.5 and 18664.8 tonnes, respevtively. During these periods, kutum predominated and represented the highest proportion of total catch at 73.1, 74.0 and 66.9% , followed by golden grey mullet at 18.3, 13.9 and 18.7%, respectively. K values calculated 0.22, 0.15 and 0.14 year-1 and L∞ were 66.0, 62.7 and 70.0 cm for kuttum, golden grey mullet and common carp, respectively. The instantaneous coefficient natural mortality were estimated as 0.386 and 0.35 year-1 for kutum and golden grey mullet, respectively. During three periods, the exploitation rates were 0.789, 0.584 and 0.614 for kutum and 0.71, 0.75 and 0.61 for golden grey mullet, respectively. In the years 2007-2007, 2008-2009 and 2009-2010, the total biomass, from the biomass-based cohort analysis were 56600, 62090 and 61590 tonnes for kutum and and MSY estimated about 24733.7 and 8550.4 tones for kuttum and 11040, 11900 and 14460 tonnes for golden grey mullet, respectively. The ABC (acceptable biological catch) were estimated as 8000 and 2200 tonnes.

The aim of the present study was to investigate the age structure, length-weight relationship, sex ratio, sexual maturity stages, growth parameters, natural and fishing mortality coefficients of three species of kilka including common, anchovy and bigeye kilka. The fork length–weight relationship of common, anchovy and bigeye kilka were calculated as W=0.000153 FL2.37, W=0.000349 FL2.18 and W=0.00160 FL2.97, respectively. The parameters of the von Bertalanffy growth curve for length were L∞ = 143.5 mm, K = 0.30 yr-1 and t0 = -1.02 yr for common kilka L∞ = 151.9 mm, K = 0.28 yr-1 and t0 = -1.12 yr for anchovy kilka L∞ = 148.6 mm, K = 0.46 yr-1 and t0 = -0.18 yr for bigeye kilka. The instantaneous coefficient of natural mortality of common, anchovy and bigeye kilka were estimated as 0.671, 0.633 and 0.881 yr-1, respectively. The current exploitation rates of three species were estimated as 0.55, 0.41 and 0.26, respectively. The results suggest that common kilka stock is under over-fishing now.

Seasonal distribution of species composition, cell abundance and biomass of phytoplankton of the Caspian Sea were investigated in 2005. This survey were fulfilled in 6 transects and 26 stations A total of 260 samples were collected during winter to autumn in the southern part of Caspian Sea. Totally, 163 species of phytoplankton were identified (71 species Bacillariophyta, 31 species Chlorophyta, 27 species Cyanophyta, 21 species Pyrrophyta, and 13 species Euglenophyta). Cell abundance and biomass of Bacillariophyta were high in centre, while biomass and cell abundance of Pyrrophyta were dominant in the middle as well as parts of the Sea, respectively. The overall total average of cell abundance and biomass of phytoplankton were 56.30± 30.97 ×106cells/m3 and 221.70±75.87 mg/m3, respectively. Bacillariophyta accounted for 47% in cell abundance, and Pyrrophyta consisted of 53% of the phytoplankton biomass. Maximum phytoplankton population was recorded in winter due to Bacillariophyta and the maximum biomass in spring due to Pyrrophyta. The maximum density of Bacillariophyta was in winter and autumn while maximum biomass was observed in spring due to bigger size of Bacillariophyta such as Rhizosolenia calcar avis and Nitzschia sigmoidea followed by Pyrrophyta with high cell abundance throughout the year.

We evaluated the stocks of Huso huso in the south Caspian Sea along Iranian coasts using data on different population parameters such as length, age, weight, catch and catch per unit effort changes. The study covered data from 1971 to 2003. The stocks and catch rate of H. huso shows a decrease during the last three decades. The recorded catch for the years 1971-1972 was 74 tons with 5.55kg catch per unit effort which was decreased to 38 tons with 0.26 kg per unit effort in 2003 in gillnet fishery and the same trend was observed in beach seine fishing. The data shows that during 1990 to 2003, the average length of the fish has increased from 192.8 to 216.2 centimeters and the average weight has improved from 73 kg to 116.3 kg. Age frequency comparison between the catch of the years 1990 and 2003 showed that with time, older age classes replaced the younger ones, hence the increase in the length and weight of the fish. Due to the decrease in the younger fish and the increase in illegal fishing, it is anticipated that the fish stocks will suffer a decrease in future.

This paper examines the changes in the population biology and biomass of common kilka (Clupeonella cultriventris caspia) in the Iranian waters of the Caspian Sea from 1995-2004. For most years during this 10-year period, we estimated the age structure of the catch, length-weight relationship, von Bertalanffy growth parameters, condition factor, sex ratios, maturity stages determined from ovarian analysis, natural and fishing mortality, age at first capture and biomass. Growth parameters were estimated as L∞=132mm, K=0.259/yr, t0=-1.285/yr. The instantaneous coefficient of natural mortality was estimated at 0.506/yr and the instantaneous coefficient of fishing mortality varied during the 10-year period between 0.125/yr to 1.487/yr. Biomass of the common kilka increased from about 16,000mt in 1995 to more than 41,000mt in year of 2002. This increase in common kilka was simultaneous with a sharp decline in anchovy kilka, changes in zooplankton abundance and composition, and especially increase in zooplankton species used by common kilka. We concluded that at the present time, the stock of common kilka is being over-fished.

Kilka, a pelagic fish feeding on zooplanktons, are the most abundant fish genus in the Caspian Sea. There are three species of the fish living in the Sea including anchovy (Clupeonella engrauliformes), bigeye (C. grimmi) and common kilka (C. cultriventris). All three species live in the coastal waters of the Sea and comprise part of the commercial catch in the area. The relative frequency of the bigeye ranked second after anchovy over the years 1990-1991 with 6.84% increasing to 12.6% and 21.7% over the years 1997-1998 and decreasing in the subsequent years. We studied biological characteristics of the bigeye kilka over the years 1997-2001 in three fishing regions Amirabad, Babolsar and Anzali. In winter and earlier spring of each year, mature bigeye kilka ready to spawn were always present in the catch. The mean fork length of the fish increased from 95.87mm in 1997 to 105mm in 2000 and decreased to 102.3mm afterwards. Over the same time period, the fork length range became wider with specimens in the upper length classes representing most of the catch. We found that males were always dominant during our study comprising 60 to 90% of the catch. The caught fish consisted of six age classes 1+ to 6+. During the years 1998 to 1999, the age Classes 1+ to 3+ comprised more than 90% of the catch. In the year 2000, we observed a decrease in the age classes 1+ and 2+ and an increase in the age classes 4+, to 5+ compared to that of the previous years. In the year 2001, the age classes 3+ and 4+ decreased and the age classes 5+ and 6+ increased. In recent years, the relative frequency of the bigeye kilka has decreased as a result of the attack by the Mnemiopsis leidyi, but fork length range of the fish has increased and bigger and older fish are dominant in the catch.

In an attempt to recognize the harmful fishing times and locations for sturgeons, we used catch statistic to evaluate by-catch of sturgeon juveniles during beach seine fishing over the years 2001-2002 in Mazandaran Province. We found that over the fishing period, 23760 hauls were conducted during which 103000 sturgeons were caught. The highest by-catch occurred in October (37% of the catch) and the lowest occurred in January (5% of the catch). The maximum sturgeon catch per haul was 14.2 in autumn decreasing through the year with 1.26 sturgeon fish caught in each haul in spring. The species composition of the by-catch sturgeon juveniles was determined to be Persian sturgeon (54%), Stellatus sturgeon (37%), Beluga (6%), Russian sturgeon (2%) and Spiny sturgeon (1%).

Mullet and other bony fishes are caught by beach seine in Iranian coastal zone in Golestan, Mazandaran and Guilan provinces. The catch and CPUE trend of mullets were compared during 1993 to 2001 and some biological characteristics such as: species composition, length, weight, K and age of Liza aurata and L. saliens were analyzed. In 1990s, the results showed that amount of catch has been increased and the maximum catch occurred in 2001. CPUE decreased from 114 kg (in each seine) in 1993 to 43 kg in 1996 whereas 2001 increased to 66.4 and 78.4 kg in 2000 and 2001, respectively. The mean fork length, weight and K for L. aurata species were measured 32.7 and 32.3 cm, 418.3 and 419.8 g and 0.61 and 0.93 and for L. saliens species were 27.5 and 25.1 cm, 224.7 and 179.1 g and 0.91 and 0.71 for years 2000 and 2001, respectively. According to this data in spite of increasing in catch, CPUE of L. aurata has increased and there are no changes in respect of biological aspect. Therefore, it was concluded that this species is harvested of a sustainable level.

The alien ctenophore Mnemiopsis leidyi which was transported from the Black Sea into the Caspian Sea at the end of 1990s has been negatively affecting ecosystem in this new environment. In this study, spatial and temporal distribution of M.leidyi were studied from a total of stations located along three transects (Amirabad, Babolsar and Nowshar) in the Eeastern Iranian coasts of the Caspian Sea (Mazandaran province) during July 2001 to November 2002. M. leidyi acheived maximum biomass 1024.5 g/m^2 in August-October 2002. Minimum biomass (1.5 g/m^2 of ctenophore were measured in December-Jaunuary 2001. The highest biomass was at the stations with 10m bottom depth (570.7 g/m^2 in autumn and lowest biomass (75.9 g/m^2) was obtained at a station with a 50 m bottom depth in winter. The highest average biomass (641.2 g/m^2) were measured in ~irabad region and the lowest biomass (207.5 g/m^2) observed in Nowshar region. The young specimens (

Kilka is one of the important and commercial fishes in the Caspian Sea and also in the Iranian waters. In this study, the catch and CPUE data collected from Mazandaran province waters during 1996-2000 were compared and analyzed. The results indicated a significant difference due to CPUE in different years. The fishing operations were carried out during night-time with duration of 7.78 to 8.22 hours. The maximum catch with 42.8% of total catch were caught in October, November and December; and on the other hand the minimum catch (2697 tons) was determined in June. There were a significant difference among the means of catch and CPUE in different months. The CPUE of Amirabad landing (554.2 kg/h) was more than Babolsar landing (P

Age and growth of Bigeye Kilka, Clupeonella grimmi, were studied in Iranian waters of the Caspian Sea from early May 2006 to April 2007. The sagitta otoliths were removed for each 5 mm length interval up to a total number of 262 fish. Fork length and weight ranged from 92.5 to 142.5 mm and 4.2 g to 23.4 g, respectively. The largest length-groups was observed from December to February and the lowest in April, which was coincided with spawning period and feeding during wintering, respectively. The overall sex ratio (male:female) was 0.33:1 which differed significantly from the expected ratio of 1:1. The length-weight regression was W= 0.0000744 FL^3.14 for females and W=0.0000341FL^3.16 for males, indicating the Caspian Bigeye grew isometrically for both sexes. Age determination based on otoliths readings showed that the population was composed of six- groups from 2 to 7 years old which observed a rapidly growth during the second year. In the age compositions, the four years old specimens with a mean fork length and weight 115.5±7.8 mm and 11.9 ± 2.8 g were the most abundant age group and accounted for 40.1%. The condition factor was 0.7-0.8 which varied in difference months and coincided to the gonad development. Age-at-length data were used to determine von Bertalanffy growth parameters for this population in both sexes, indicating that K value and L∞ of females was more than that of males. The results showed that C. grimmi is a rapidly-growing species in the southern parts of the Caspian Sea.