Search

Since the 1990s, anthropogenic activities have been the major direct or indirect threats to the structural and functional organization of the unique ecosystem of the Caspian Sea (CS). This study attempts to investigate the relationships between fish community structure and environmental parameters and to analyze the Abundance Biomass Comparison (ABC) in the CS. The input data, including catch data by species and environmental parameters, were collected from 1996 to 2017. Of the 13 bony fish species identified, only two species Rutilus kutum and Chelon aurata accounted for 47.14% and 62.65%, and 40.80% and 29.34% of CPUE and NPUE, respectively. DisTLM revealed that five environmental variables showed a significant linear relationship with the NPUE resemblance matrix. Based on the AIC criteria, the combination of year, precipitation, SST_Apr, SSL, SST, GTA, Iranian rivers, and Volga discharges explain 80.3% of the total variability. Based on the ABC curves and W statistics, it was concluded that the fish assemblage was environmentally stressed from 1996 to 2003. The Shannon diversity index (H´) showed a decreasing trend, suggesting that fish species have been exposed to increasing stress over the past 22 years. Considering the current environmental conditions (downward trend in SSL river discharge and increase in SST) and anthropogenic activities, it appears that the downward trend will continue in the future.

Persian sturgeon, Acipenser persicus Borodin, has been the most significant proportion of Iranian commercial sturgeon catches in the Caspian Sea over in the last three decades. This endemic species has suffered continuous population declines from the impact of anthropogenic factors. The present study filled in information gaps on underlying population biology parameters, evaluated the population status, and determined the vulnerability risk of the stock extinction of Persian sturgeon in the south Caspian basin of Iran. Growth parameters were L ∞ = 224.7 cm, K = 0.058 years−1, t 0 = -3.4 years. Sexual maturity of 50% for males and females was FL = 127.2 cm and 137.5 cm, respectively. The long-term age composition data showed 35 age groups, and the ages of 14–18 years comprised 80% of the total catch. Natural mortality was 0.123 years−1, and fishing mortality ranged between 0.104 and 0.331 years −1. The total biomass trend decreased and collapsed from 6,071.3 tons in 1990–91 to 144.1 tons in 2014–15. Although >93% of the catch included maturing specimens, the Persian sturgeon stock is now critically endangered because of several anthropogenic factors.

There is a significant lack of data for the biological parameters of beluga or great sturgeon, the largest fish in the Caspian Sea. The age, growth and fisheries indices for the stock status of beluga was investigated in the south Caspian Basin of Iran between 1990 and 2011. Fork lengths ranged between 113-420 cm and weights from 8.0 to 725.0 kg. The growth parameters were L ∞ = 440 cm, K = 0.027 year−1, t 0 = − 5.8 years. The age at first capture (t c ) was 13.1 years. The long-term age composition data showed age up to 63 years, and the ages 12-19 years comprised 76.7% of the total catch. The generation length was 33 years. The values of “KF” were close to 1 or >1, indicating that beluga sturgeon is in a favorable condition in the southern Caspian Sea. The length distribution showed that 24.2% of the catch is comprised of juveniles. Based on the age structure and age at first maturity, recruitment and growth overfishing occurred in beluga stocks. Therefore, increased length or age at first capture in future fishery policies should be implemented. The mega-spawners represented 4.4% of the fish captured and revealed an unhealthy population structure.

Postoji značajan nedostatak podataka o biološkim parametrima morune Huso huso, najveće ribe u Kaspijskom moru. Ovim istraživanjem određivala se dob i indeksi rasta morune u svrhu procjene stanja njenog fonda u južnom Kaspijskom bazenu Irana od 1990. do 2011. Duljina vilice kretala se u rasponu između 113-420 cm, a masa od 8,0 do 725,0 kg. Parametri rasta bili su L∞ = 440 cm, K = 0,027 godina−1, t0 = - 5,8 godina. Dob pri prvom ulovu (tc) bila je 13,1 godina. Podaci o dugoročnoj strukturi dobi morune ukazali su na dob do 63 godine, a jedinke u dobi od 12-19 godina sačinjavale su 76,7% ukupnog ulova. Dužina generacije bila je 33 godine. Vrijednosti KF indeksa bile su blizu 1 ili > 1, što ukazuje da je moruna u povoljnom kondicijskom stanju u južnom Kaspijskom moru. Raspodjela vrijednosti dužine morune ukazala je kako 24,2% ulova čine juvenilni primjerci. Natemelju dobne strukture i dobi pri spolnom sazrijevanju, novačenje i prekomjerni ribolov utjecali su na zalihe morune. Ovim se, u budućim ribarstvenim politikama, preporuća povećati dužinu ili starost morune pri ribolovu. Mega-mrijesni primjerci morune su predstavljali 4,4% ulovljene ribe, što ukazuje na neujednačenu strukturu populacije., There is a significant lack of data for the biological parameters of beluga or great sturgeon, the largest fish in the Caspian Sea. The age, growth and fisheries indices for the stock status of beluga was investigated in the south Caspian Basin of Iran between 1990 and 2011. Fork lengths ranged between 113-420 cm and weights from 8.0 to 725.0 kg. The growth parameters were L∞ = 440 cm, K = 0.027 year−1, t = − 5.8 years. The age at first capture0(tc) was 13.1 years. The long-term age composition data showed age up to 63 years, and the ages 12-19 years comprised 76.7% of the total catch. The generation length was 33 years. The values of “KF” were close to 1 or >1, indicating that beluga sturgeon is in a favorable condition in the southern Caspian Sea. The length distribution showed that 24.2% of the catch is comprised of juveniles. Based on the age structure and age at first maturity, recruitment and growth overfishing occurred in beluga stocks. Therefore, increased length or age at first capture in future fishery policies should be implemented. The mega-spawners represented 4.4% of the fish captured and revealed an unhealthy population structure.

This research is done with aim of determining the accumulation of heavy metals Fe Zn Cu and Cd in different tissues of Caspian Marin shad Alosa braschnikowi in south area of Caspian Sea Babolsar Then species of fishes were collected from commercial fishing randomly The density of samples rsquo heavy metals after biometry length and weight and tissue isolation and chemical digestion was measured by the Flame atomic absorption The concentration of Fe in the tissues was such as gonad gt gills gt skin gt muscle the Zn is such as muscle lt gills lt skin skin gt gills gt muscle and Cu was such as Muscle

Sturgeons are the most important principal market species in the Caspian Sea. In the present study, measurement of blood parameters was carried out with the aim of evaluating the normal value of hematological and serum biochemical parameters of brood stocks Acipenser persicus during spawning season. Blood samples were collected from 36 brood stocks of A. persicus (18 males and 18 females) during the spawning season. Higher value of red blood cells, white blood cells, haemoglobin, haematocrit was observed in male breeders with significant differences between female breeders (p>0.05). Haemoglobin and haematocrit value in this study was within the range of 8.70 to 9.2 g/dL and 29.73% to 30.26%, respectively. The statistically significant differences between mean corpuscular volumes, mean corpuscular haemoglobin, lymphocyte and neutrophil percentages, aspartate aminotransferase, alkaline phosphatase and creatine kinase were observed in the male and female brood stocks. It is concluded from this study, some of the hematological and serum biochemical parameters of male and female A. persicus breeders were significantly varied from each other. In comparative investigation with earlier reports, the values of red blood cells, haemoglobin and haematocrit are highly varied due to age variations of fish. However, further studies are necessary to understand the impact of sexual, age, size, length, and season and habitat variation. Serum biochemical parameters can be used for confirming the maturity of A. persicus and monitoring any changes in the water quality parameters and soil.

The invasive ctenophore Mnemiopsis leidyi was first recorded in the Caspian Sea in 1995 in the southern part of the sea (Iranian waters). This study assesses the magnitude of the M. leidyi bioinvasion impacts on the region’s ecosystem using the biopollution level (BPL) index. For this purpose, biomass and distribution range of the invasive ctenophore were analyzed for the period 1996–2010. In addition, the impacts of the IAS on native species, communities, habitats and ecosystem functioning were assessed. The BPL for the period of our study remained relatively stable at the level 4 (massive). The BPLs caused by M. Leidyi in the southern Caspian Sea were compared with those of the Black and Baltic Seas. The method used in this study seems to be applicable for evaluating spatial and temporal variations of the invasive impacts of gelatinous zooplankton in other marine regions.

Betanoda virus is an emerging problem in several marine fish species in various geographic areas all over the world. In recent years, mullets stock of the Caspian Sea decreased dramatically and a betanoda virus like-agent was introduced as the cause of mullet’s mortality. The main objective of the present study is to compare hemato-biochemical parameters in healthy and infected sharpnose mullets (Liza saliens) to betanoda virus like-agent. The adult sharpnose mullets (34 clinically affected fish + 34 apparently healthy fish) were captured from the southeast the Caspian Sea from 2012 to 2013. All of the captured fish were 4 or 5 years old. The main clinical sings of infected fish were lethargy, severe abdominal distention, abnormal swimming and hyperinflation of swim bladder. The results showed that the weight and total length of infected fish were significantly lower than the healthy fish. The results of histopatological evaluation and indirect florescent antibody test were confirmed the presence of a betanoda virus-like agent in infected fish. The diseased fish were severely anemic (hypochromic macrocytic anemia) and had a serious haemopoietic disorders. The anemia associated with a sever leukopenia, a significant rise of neutrophils and immature neutrophils and a significant decries of lymphocytes percentage. Total protein, albumin and total immunoglobulin levels were significantly reduced in the serum of infected fish, while the activities of aspartate aminotransferase and alanine aminotransferase significantly increased when compared to the healthy fish. These results suggested that the feeding of the infected fish to betanoda virus like-agent were disturbed and it could be cause haemato-biochemical disorder and mortality of the fish in Iranian water of the Caspian Sea.

Predicting and modeling of habitat preferences of fish is a very important issue for aquatic management. Classification trees (CTs) were used to predict the habitat preferences of the Caspian kutum (Rutilus frisii kutum, hereafter kutum) in the southern Caspian Sea. The applied model was optimized with genetic algorithm (GA) and greedy stepwise (GS) to select the most explanatory variables for predicting the presence/absence of kutum. The suitability index was considered to determine the quality and suitability of fish habitat in the sea. The results of Paired Student’s t tests showed that there was a significant difference between predictive performances of models before and after variable selection methods. Both optimizers improved the predictive power of CTs and resulted in a better understanding of CTs by making a selection of the sea characteristics that were used as inputs to the models. The results show that the effect of different seasons, sea depth, and photosyntheticaly active radiation were the main predictors affecting the habitat preferences of kutum in the Caspian Sea. Constructed trees in combination with GA and GS showed high capability when applied to predict the habitat preferences of this valuable commercial fish species. Determining the habitat needs of the target fish will enhance local fisheries performances and the long-term conservation planning of the fish to implement the ecosystem-based management in the Caspian Sea.

After the arrival of the invasive species (Mnemiopsis leidyi) in the Caspian Sea (in 1999) significant changes have been occurred in the ecosystem. In the present study, the data concerning the period 1996 to 2010 (extracted from the relevant research projects) were analyzed. The period was classified into two phases, before and after the species invasion (1996 and 2001-2010). In our study, the impact of the invasive species on the structure of southern Caspian zooplankton communities was assessed during the period 2001-2010, quantitatively.The combination of abundance and distribution range of the species (ADR) during the period 2001-2009 and the year 2010 were evaluated as E (occurrence in high numbers in all localities) and D (occurrence in moderate numbers in all localities), respectively. Considering the obtained results, the year 2001, in which the relative biomass was more than 90 percent, could be considered as the expansion phase and the following years (2002-2010) as the adjustment phase. With regards to the loss of the keystone and some other native species after the invasion of M. leidyi (2001 to 2010), the impact of the invasive species on the structure of southern Caspian zooplankton communities was assessed as massive (C4).

The relationship between species and habitat is important in ecosystem-based fisheries management. Habitat suitability index (HSI) modeling is a valuable tool in ecology and can be used to describe the relationship between fish abundance and ecological variables in order to estimate the suitability of specific habitats. In the present study, an HSI model was applied to determine suitable habitats for the Caspian kutum (Rutilus frisii kutum), an important commercial species in the southern Caspian Sea. An arithmetic mean model (AMM) was found to be the most appropriate model for describing the relationship between two of the environmental variables investigated (depth and benthos biomass). However, a geometric mean model explained the evident relationship when all four environmental variables were used (depth, benthos biomass, photosynthetically active radiation and sea surface temperature). The areas with an HSI > 0.5 had over 85 % of the total catch indicating the reliability of the prediction of the Caspian kutum habitat using the AMM. The present study showed that depth and substrate structure are the most important environmental variables for the Caspian kutum to select its habitats, and between remotely sensed data, chlorophyll a, photosynthetically active radiation and sea surface temperature are the most critical parameters for near real-time prediction of the Caspian kutum habitat.

Changes in length, weight and fecundity of mature females of the Kutum (Rutilus frisii kutum) were compared for the periods 1948–1950, 1974 and 2007 in Iranian waters of the Caspian Sea. The average fork length decreased from 54.1 over 44.7 to 43.9 cm and the average weight from 2181 over 1295 to 1210 g. However, the average condition factor has remained fairly constant and varied between 1.35 and 1.38. The potential fecundity of the Kutum for the three periods also decreased from 106,800 over 74,600 to 64,400 eggs. Size and fecundity of the Caspian Kutum has therefore sharply declined during the last six decades. The reduction of fecundity is apparently the consequence of the shift towards smaller fish size.

Phylogenetic relationships among all described species (total of 5 taxa) of the shrimp genus Penaeus, were examined with nucleotide sequence data from portions of mitochondrial gene and cytochrome oxidase subunit I (COI). There are twelve commercial shrimp in the Iranian coastal waters. The reconstruction of the evolution phylogeny of these species is crucial in revealing stock identity that can be used for the management of fish industries in Iran. Mitochondrial DNA sequences were used to reconstruct the phylogeny of the Penaeus species of marine shrimp. For this purpose, DNA was extracted using phenol-chloroform well as CTAB method. The evolutionary relationships among 5 species of the shrimp genus Penaeus were examined using 610 bp of mitochondrial (mt) DNA from the cytochrome oxidase subunit I gene. Finally the cladograms were compared and the resulting phylogenetic trees confirmed that the Iranian species originated from the Indo-West Pacific species. The Iranian species, which were not grouped with the other Penaeid taxa, seem to always form a sister-clade to the Indo-West Pacific species with strong bootstrap support of 100%. Although the Iranian species + Western Hemisphere clade is paraphyletic in our gene tree, the bootstrap support is high. However, we still lack any comprehensive and clear understanding of phylogenetic relationships in this group.

In this study, the influence of height and mesh size of beach seine net on the amount of fishing, length frequency and species composition of caught fish was examined. Two beach seine nets with 20 and 24 m heights and each net with 30 and 33 mm center part mesh size were used by two fishing cooperatives during 2008 and 2009. Rutilus frisii kutum and Mugil auratus were selected as a target fish in this study. Catch and biological data were measured and recorded. Results indicated that the height and mesh sizes used in the present study had significant effect on the catch characteristics in terms of amount of species, catch rates and species composition. Amount of catch was reduced in 24 m beach seine in comparison with 20 m height net both in 2008 and 2009. There were significant differences between fish caught by 30 and 33 mm mesh size net in 2008 and 2009. With an increase in size of mesh net from 30 to 33 mm, amount of R. frisii kutum catches increased but amount of M. auratus catches decreased. There was no any especial effect of height and mesh size on fish length. Amount of bycatch also increased in relation to net height from 20 to 24 m. Key words: Beach seine net, height, mesh size, quantity and quality of fishing, Caspian Sea.

Monitoring for 6 years (2001–2006) showed that the population explosion of the alien ctenophore Mnemiopsis leidyi in the southern Caspian Sea coincided with a decline in the abundance and species number of mesozooplankton. While this decline appeared to have reduced the nourishment of sprat (also known as kilka), it seemed to have affected phytoplankton favorably mainly due to the decrease in grazing pressure. During 2001–2002, when M. leidyi abundance and biomass were at their highest levels, abundance of dinoflagellates and cyanophytes exceeded that of diatoms. Before the invasion (1996) and in some years after the invasion (2003, 2004 and 2006) diatom abundance was higher than the abundance of other groups. In September 2005, an unprecedented bloom of the toxic cyanophyte Nodularia sp. was observed in the southern Caspian Sea. Disappearance of edible zooplankton such as Eurytemora spp. was among the first changes observed after the expansion of M. leidyi in the area. Some changes in the macrobenthic fauna were also conspicuous after the increase of this ctenophore. While the biomass of some deposit feeders, such as the polychaete Nereis diversicolor and oligochaete species increased, benthic crustaceans decreased sharply in abundance during 2001–2003 and completely disappeared during 2004–2006. Iranian catches of kilka, the most abundant and widespread zooplanktivorous fish, decreased significantly in the southern Caspian Sea after 1999. Iranian landings of kilka dropped ~70% from 69,070 ± 20,270 t during 1995–2000 to 23,430 ± 12,240 t during 2001–2006, resulting in a loss of at least 125 million US dollars to the economy. There were also changes in the total catches of large predators such as the kutum and mullet, which mainly feed on kilka, between 1991 and 2006.

Recent changes in sea level of the Caspian Sea and ecological impacts caused by the invasive ctenophore ( Mnemiopsis leidyi ) have altered the ecosystem. A consequence is the changes in the absolute and relative abundance of the commercially important anchovy kilka ( Clupeonella engrauliformis ) in Iranian waters. To adjust to this change more rigorous management of this fishery is required. This paper examines the maximum sustainable yield (MSY) and fishing intensity at MSY. The paper presents estimates of f MSY , yield-per-recruit and spawning biomass-per-recruit under various harvest strategies of F max , F 0.1 and F 40% . We propose a method for estimating acceptable biological catch (ABC) that accounts for large differences in the quality and quantity of information and available data. The MSY and f MSY were estimated 44,652 mt (metric tons) and 18,609 vessel × nights (a unit of effort). The ABC was estimated at 2190 mt in 2004. In 2005, however, the catch of anchovy kilka was about 4300, over twice the estimated ABC. In 2008 (from January to October) the catch declined to 220 mt. The analyses indicate that overfishing, especially between 2005 and 2008, is the main reason of the collapse of anchovy kilka in the Caspian Sea.

Summary The objective of the study was to determine some reproductive parameters in the golden grey mullet (Liza aurata Risso, 1810) during two periods half a decade apart while also trying from limited data to identify changes in fecundity over the past half century. Maturity and fecundity of golden grey mullet caught in Iranian waters of the Caspian Sea is not well documented and were thus studied during several seasonal cycles during 2002–2004 to establish basic data on reproduction in the area. The fork length (FL) of 462 sampled fish was between 22.1 and 51.9 cm. The fork length–weight relationship derived from all fish was W = 0.0118FL2.964. Overall male to female ratio was 1 : 1.42. The reproductive season extended from October to December. Fifty percent of sexual maturity was at FL 26.0 cm. Mature gonads were present in 20% of fish at age 3, 63% at age 4, 88% at age 5, and 97% at age 6. Individual absolute fecundity of the golden grey mullet ranged from 113 386 to 1.47 million eggs, with a mean (±SD) of 451 963 (±274,114.2). An overlap exists between the spawning and fishing seasons. Therefore, the start of the fishing season should be delayed for 1 month in order for stocks to complete their spawning.

This paper examines the changes in the population ecology parameters and biomass of golden grey mullet ( Liza aurata ) in Iranian waters of the Caspian Sea from 1991 to 2005. For most years during this 14-year period, we estimated the age structure of the catch, length–weight relationship, von Bertalanffy growth parameters, condition factor, natural and fishing mortality and biomass. Growth parameters were estimated as L ∞ = 62.7 cm, K = 0.15 year −1 , t 0 = −0.23 year −1 . The instantaneous coefficient of natural mortality was estimated as 0.350 year −1 and the instantaneous coefficient of fishing mortality varied during the 14-year period between 0.111 to 0.539 year −1 . Biomass estimates of golden grey mullet, from the biomass-based cohort analysis were increased from 13,527 mt in 1991–1992 to 23,992 mt in 2002–2003. In 2004–2005, it was estimated to be 23,658 mt. We concluded that at the present time, the stock of golden grey mullet is not being over-fished.

Through most of the last century, three endemic kilka species supported major commercial species in the Caspian Sea. It is clear that catches and abundance of all species have changed, but catch and sampling data are limited and stock assessments are inadequate. Recent changes in the Caspian Sea ecosystem have occurred as a consequence of climatic environmental change (sea level change) and ecologic change caused by the invasive ctenophore Mnemiopsis leidyi. This paper examines the effects of these changes on the population biology and biomass of anchovy kilka Clupeonella engrauliformis in Iranian waters of the Caspian of catch, length-weight relationship, von Bertalanffy growth parameters, condition factors, sex ratios, maturity stages determined from ovarian analysis, natural and fishing mortality, age at first capture, and spawning biomass. The instantaneous coefficient of natural mortality was estimated as 0.473/year and the instantaneous coefficient of fishing mortality varied during the 10-year period between 0.541 and 2.690/year. Biomass of anchovy kilka declined from about 186000 t in 1996 to less than 12000 t in 2004. Recent high fishing rates were not sustainable after the introduction of Mnemiopsis, so overfishing is part of the explanation for the collapse of anchovy kilka in the Caspian Sea.

To comprehensively manage an ecosystem such as that of the Caspian Sea, the world’s largest lake, detailed knowledge of the habitat traits of the living organisms in the ecosystem is essential. The present study examined environmental variables and used the Habitat Suitability Index (HSI) model to determine the most preferred seasonal habitat and optimal environmental range of Caspian shad (Alosa spp). The fish preferred deep waters with low levels of total organic matter and sea level anomaly in winter and productive areas with a high concentration of chlorophyll-a (Chla) and relatively high benthos biomass in spring. The number per unit area (NPUA)-based HSI model determined that the geometric mean model (GMM) was the optimal model for defining a suitable habitat in winter. For spring, the arithmetic mean model (or GMM) in the NPUA-based HSI model most accurately predicted preferred habitat for Caspian shad. The average NPUA in both seasons increased with the HSI; areas with an HSI of between 0.4 and 0.6 in spring and between 0.6 and 0.8 in winter had a high percentage of total catch. Areas with an HSI of more than 0.5 had over 91% and 63% of the total catch in spring and winter, respectively, demonstrating the reliability of the NPUA-based HSI model in predicting Caspian shad habitat. The present study shows that remotely sensed data plus depth are the most critical environmental variables in Caspian shad habitats and that Chla and SLA are the most critical remotely sensed parameters for near real-time prediction of Caspian shad habitat.

The present study investigated the effects of different dietary nettle (Urtica dioica) levels on biochemical, hematological and immunological parameters in beluga (Huso huso). Fish were divided into 4 groups before being fed for 8 weeks with 0%, 3%, 6% and 12% of nettle. The blood samples were collected on week 4 and 8. The use of nettle did not significantly change the mean cell volume, mean cell haemoglobin, lymphocytes, eosinophils, albumin, glucose, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and lysozyme activity on week 4 and 8. After 4 weeks, the total red blood cell (RBC) and hematocrit (Ht) showed a significant increase in 12% nettle group compared to the 3% nettle and control groups but haemoglobin (Hb) had a significant change in 12% nettle compared to the control. At the same time was not found a significant change in the mean cell haemoglobin concentration (MCHC), total white blood cell (WBC), neutrophils, respiratory burst activity (RB), total immunoglobulin (Ig) and total protein (TP), triglyceride (Tri) and cholesterol (Chol). After 8 weeks, the fish treated with nettle exhibited significantly increase in neutrophil and Hb levels compared to the control and between treatment groups, 12% nettle group shown the highest Hb while RBC and Hct values significantly rose in fish fed by 12% compared to the control. Supplementing 6% and 12% nettle increased the WBC and MCHC compared to the other groups. The group fed 12% showed a highly significant difference in RB, TP and Ig after 8 weeks. However, Tri and Chol were significantly decreased in the juvenile beluga fed by the 6% and 12% nettle diet compared to the other groups. The results suggest that by using this herb there will be an improvement in hemato-biochemical parameters and immune function of juvenile beluga.

The length-weight relationship, age, growth parameters, sex ratio, mortality and exploitation rate of Salmo trutta fario were determined in Lar dam. The sex ratio (male: female) was 1:1.84 which differed significantly from the expected 1:1. The length-weight regression was (females) and (males) indicating a negative allometric growth for both sexes. Growth parameters were estimated as L∞ = 45.0 cm, K = 0.27 yr-1, t0 = -0.23 yr. The instantaneous coefficients of natural, total and fishing mortality were estimated as 0.40 yr-1, 0.75 yr-1 and 0.35 yr-1. The results showed that S. trutta fario is moderately a rapidly-growing species in Lar dam. The exploitation rate was 0.47. Therefore, the population appeared to be in good condition in 2004 Title page has incorrect date 2011

This paper examines the changes in biomass and condition index in relation to stock enhancement of Kutum (Rutilus frisii kutum) in Iranian waters of the Caspian Sea during 1991-2011. Over this period, the condition factor of female and male Kutum showed decreasing trends. The average condition factor declined from 1.48 in 1991-1992 to 1.29 in 2010-2011 for females and from 1.40 in 1991-1992 to 1.20 in 2010-2011 for males. The instantaneous coefficient of natural mortality was estimated at 0.39/yr and the instantaneous coefficient of fishing mortality varied during the 20-years period between 0.20/yr to 1.04/yr. Biomass estimates of Kutum using biomass-based cohort analysis increased from about 34,700 mt in 1991-1992 to 40,900 mt in 1993-1994, declined to 28,800 in 2001-2002, increased to 56,900 in 2006-2007, and again declined to 42,600 in 2010-2011. The total number of released Kutum fingerlings increased from about 110 millions in 1991 to 400 millions pieces in 2010. Although there is a significantly positive correlation between fingerlings released and recruitments, it appears on the other hand that condition factor is adversely influenced by the number of fingerlings released. Moreover, over the recent period, biomass and catches do not seem to benefit so much from the increasing efforts in fingerlings release. We concluded that more research should be conducted to determine the desirable level of artificial propagation.

Fish sampling were carried out using beach seines during the fishing season from early October 2006 to mid April 2007. The gonadosomatic indexes (GSI) in range and average for female and male were 0.03 to 40.28 (5.70 ± 6.48) and 0.13 to 16.71 (3.39 ± 2.33), respectively. The GSI indicated that the reproductions of R. f. kutum were occurred during March-April, with the highest average value of 6.52 for males and of 17.00 for females in April. Fifty percent of length maturity (L ) at FL = 37.78 cm was recorded. The absolute fecundity ranged from m50% 15,723 for a three-year old to 130,737 eggs for an eight-year old female, with a mean of 60435 ± 24889. The relationship between fecundity (F) and fork length (cm) was represented by the formula: Fec. = 6616FL+25916. The von Bertalanffy growth parameters was: L =67.5cm, K=0.21 year , t =-0.10 for throw population of kutum. 8 0 1 The maximum spawning migration into the rivers based on GSI occurred significantly in April but it be affected by environment of sea water layers. The results showed that the length at first maturity and fecundity of R. f. kutum reduced in southern part of Caspian Sea.

Through most of the last century, three endemic kilka species supported the ma-jor commercial species in the Caspian Sea. Recent changes in the Caspian Sea ecosystem have occurred as a consequence of climate change and ecological change caused by the invasive ctenophore Mnemiopsis leidyi. We examined the impact of these changes on the population biology of bigeye kilka (Clupeonella grimmi) in Iranian waters of the Caspian Sea from 1995 to 2001. The overall sex ratio (male:female) was 1.65:1. The length-weight regression was  0.00922 W L 2.851 (females) and  0.008021 W L 2.907 (males) indicating a negative growth for both sexes. Growth parameters were estimated as L ∞ = 142 mm, K = 0.28 yr -1 , t 0 = -1.39 yr. The instantaneous coefficient of natural mortality was estimated as 0.460 yr -1 and the instantaneous coefficient of fishing mortality varied between 0.469 to 0.980 yr -1 . Biomass of the bigeye kilka increased from about 36,900 mt in 1995 to more than 53,500 mt in 1998, but declined to less than 5,900 mt in 2001. This decrease in bigeye kilka was simultaneous with a sharp reduction in anchovy kilka due to the com-bined effects of fishing and changes in zooplankton abundance and composition soon after the appearance of Mnemiopsis leidyi in the Caspian Sea.

There have been recent changes in the Caspian Sea ecosystem, such as those due to changes in sea level or those caused by the invasive ctenophore, Mnemiopsis leidyi. It is believed that these changes had significant impacts on the absolute and relative abundance of the commercially important anchovy kilka (Clupeonella engrauliformis) and common kilka (C. cultriventris caspia) leading to decline in the former and increase in the latter species in the Iranian waters. Consequently, more rigorous management is required. The mixed-species yield-per-recruit was applied to the Iranian conical lift-net. This study showed that the pooled fishing mortality at F40% was 0.70 yr-1 which is higher than fishing mortality of main species of anchovy kilka, but lower than the pooled fishing mortality at F0.1 (0.75 yr-1). The ABC under the best information available, at pooled species reference points for two species of anchovy and common kilkas, was estimated to be 8260mt. An analogous goal in a multispecies situation would be fishing at a fishing level, denoted Fws, such that the fishing rate for the weakest stock (in this case; anchovy kilka) does not exceed its F40% rate. Under this harvest strategy at F40% for anchovy kilka, it is suggested that the ABC of pooled species of anchovy and common kilkas was estimated 7920mt to be selected in kilka fishery in Iranian waters.

The population dynamic parameters of Vimba vimba persa (Pallas, 1811) were investigated from 994 specimens collected in the Iranian waters of the Caspian Sea from October 2008 to September 2009. Fork length ranged from 9.5 to 23.4 cm. Von Bertalanffy growth parameters from size-at-age data are: L∞ = 26.1 cm, K = 0.28 yr-1, to = -0.65. The length-weight relationship coefficient b for males (b = 3.128) was higher than that for females (b = 2.971). The oldest fish was 5 years old. Sex ratio was 1:1.35 (n = 935) with females predominating. Using the catch curve method, the instantaneous coefficient of total mortality Z was estimated as 1.07 yr-1. The instantaneous coefficient of natural and fishing mortality M and F were 0.58 and 0.49 yr-1, respectively. The current exploitation ratio E = 0.46 indicated that the population seems to be highly exploited, and probably not at a sustainable level.