Stock assessment of kutum (Rutilus frisii kutum) in Iranian coastal waters of the Caspian Sea

Caspian kutum (Rutilus frisii kutum) is one of the most important commercial bony fishes in Iranian coastal waters of the Caspian Sea that constitute more than 50% of the total annual catch of the bony fishes. In the fishing season of 2003-2004, 5 mobile working groups gathered biometry data in the regions Anzali, Kiashar, Noshahr, Babolsar and Torkmen. Catch statistics of bony fishes was gained from fishing and landing harbors. Total catch of the commercial bony fishes was estimated at 15.5 thousand tons from which the kutum amounted to 8477 tons, 45.5% of the total. Also, catch of the bony fishes of beach seine cooperatives was estimated at 10667 tons where the Caspian kutum comprised 5180 tons (48.65%). The catch per unit effort (CPUE) of the Caspian kutum amounted to 93.3 kg/set with the highest value recorded in Noshahr and the lowest amount observed in Anzali and Kiashahr regions. The mean fork length of the species was 36.7 plus or minus 6.1 cm showing a range of 21 to 69 cm. The mean age was measured as 3.82±1.37 years with the range of 1 to 8 years. The age groups 3, 4 and 5 years old comprised 87% of the total catch age composition. Von Bertalanffy growth parameters such as L infinity, k and t_0) were determined as 70.1 cm, 0.138/year and -1.557 years, respectively. Total mortality, natural mortality and fishing mortality rates of the species were estimated at 1.1/year, 0.28/year and 0.83/year, respectively (considering a surface water temperature of 14°C). The biomass of the fish was estimated at 25 thousand tons

Sustainable exploitation of the bony fishes in Iranian coastal waters of the Caspian Sea: Necessities and Requirements

The Caspian Sea has a high ecological and biological value due to harboring important commercial bony fishes and sturgeons. There are more than 15 species of bony fishes (excluding kilka) which are harvested by 135 fishing cooperatives in Iranian coastal waters of the Caspian Sea and 10000 fishermen are involved in exploitation of these fishes. Annually, between 20 to 24 thousand tons of commercial bony fishes as Caspian kutum, mullets, bream, pikeperch, European carp, Caspian salmon, shads and other fish species are caught in Iranian coastal waters of the Caspian Sea. Strengths, weaknesses, opportunities and threats (SWOT) in exploitation of the bony fishes have been surveyed. SWOT results were analyzed considering the long-term development plan of the Iranian Fisheries Organization for sustainable and responsible exploitation of bony fish species. The effective strategies including rehabilitation of spawning grounds in the rivers, restocking of endangered species, controlling illegal fishing and decreasing the number of beach seine fishing cooperatives were determined as required in Iranian coastal waters of the Caspian Sea

Population dynamics of Abra ovata in the coastal waters of Guilan Province (1996)

The bivalvia of Abra ovata belongs to SEMELIDAE family inhabits in Black Sea and Azov Sea; and was introduced to the Caspian Sea in 1939. This species has a significant role on sturgeons' feeding. 384 specimen of this species were studid to determine the growth rate and age composition. The results indicated that the mean length of this bivalve was measured 9.33±2.26 mm with minimum and maximum length of 3.40 and 15.0mm, respectively. There was found a significant difference between the samples of two different depths of 10 and 20m. The dominant length groups for different seasons were as follow: spring: 3-5mm, summer: 5-7mm, autumn and winter: 9-11mm. By using Bhattacharya method, 3 individual Cohorts was determined. The length- weight relationship was W=0.0008L2.97 (R2=88.35, n=383). This species has an allometric growth and the Von- Bertalanfy growth equation was calculated L_(t)= 14.5^[1 - exp-1.5(t+1.89)]. The natural mortality coefficient and relative condition factor were estimated 1.56 per year and 1.053, respectively

Stock assessment of the pick perch (Stizostedion lucioperca) in the southern coastal waters of the Caspian Sea

Pick Perch is one of the most valuable fish species of the Caspian Sea, caught commercially each year. During the fishing season of the years 2000-2001, 18 tons of the fish comprising 11% of the total commercial catch was caught in the southern Caspian Sea. Of this around 12 tons was caught using beach seine (12 tons) in the coastal waters and another three tons in Anzali Lagoon and the rest is calculated to be the amount of the fish caught without license and recording. The mean fork length, weight and age of the species as 28.11±3.12cm, 253±91.1 grams and 3.09±0.72 years respectively. Also the length-weight relationship calculated as W= 0.035*L^2.65 (R^2 = 65.66%, N= 106). The range of age groups in the catch was 2 - 5 years of which the age groups 2 and 3 comprised 78.5% of the catch. I calculated the Von Bertalanffy growth equation for the fish as: L_t =52.5*[1-exp-0.158*(t+1.852)]. The instantaneous rate of total, natural and fishing mortality coefficients were 0.95 year^-1, 0.31 year^-1 and 0.64 year^-1 respectively. The calculated exploitation ratio was 0.67. Using the cohort analysis, I estimated the biomass of the species as 31.56 tones. The Gulland's formula used to assess the minimum sustainable Yield of the fish as 13.89 tones which is lower than the total catch of the fish. Fishery return coefficient of the fish was measured as 2.87%

Trends in stocks fluctuation of Rutilus frisii kutum in the Caspian Sea

Overfishing, destniction of spawning grounds together with intensive artificial reproduction and release of Rutilus fish/ kutum fingerlings have caused remarkable fluctuations in the stocks of the fish in the Caspian Sea over the past decades. The mean catch size of the fish during periods 1937-1947, 1967-1977 and 1987-1997 were 3110, 990 and 8505 tons respectively. Also the minimum catch was recorded as 121 tons in 1964 and the maximum catch was recorded as 11175 tons in 1994. The catch per unit effort (CPUE) of the species shows high variations such that it has been 17 kg/ton in 1971, 216 kg/ton in 1989 and 112 kg/ton in 1999. The decline in CPUE in 1999 was due to increased fishing efforts of 3.8 orders of magnitude (in comparison to the year 1989) as a result of fishing cooperatives increasing in number during that period. The calculated stock biomass of the fish was 1300 tons in 1971 fluctuating between 18489 to 25400 tons in the period 1990-2000. The mean biomass of the fish in the recent past 10 years was 22750 tons which shows 17-fold increase in comparison to the year 1971. The accomplished catch in the recent 10 years has been 35 to 46 % of the annual stock. The exploitation rate being more than MSY and decreased mean weight of the released fingerlings plus lowered return rate might have caused the decrease in the stock size of the fish during 1998-1999

Spawning season, fecundity and Lm 50% of the Caspian Sea prawn (Palaemon adspersus) in the coastal waters of Guilan Province

The spawning season, fecundity and Lm50% of the Caspian Sea prawn (Palaemon adspersus) were investigated in the coastal waters of Guilan province. A monthly sampling was conducted using a bottom trawl with mesh size 3 mm in cod end in areas 0-5 and 5-10 meters deep during the year 2002. Mean total length, carapace length and weight of ovigerous female of Palaemon adspersus were 51.95±3.1 mm, 13.95+1.9mm and 2.742±0.58g (X ± S.D). Minimum and maximum total length of ovigerous specimens were 37 and 59.3mm with a weight 1.002 and 4.145 grams respectively. We found that the spawning season of Palaemon adspersus begins in April and ends in September with a peak in June. Mean fecundity of the species was 1994.5±506.6. The size at which 50% of females are mature was estimated to be 51.27mm total length

Length-length, length-weight relationship and relative condition factor of pike, Esox lucius Linnaeus, 1758, in Anzali Wetland (Southwest of the Caspian Sea)

The length-length (LLRs), length-weight (LWR) relationships and relative condition factor (Kn) of 505 specimens of pike, (Esox lucius Linnaeus, 1798) from Anzali Wetland, southwest of the Caspian Sea, were studied from April 2012 through March 2013. The length-length relationships among total length (TL), fork length (FL) and standard length (SL) for pike were found to be highly significant (r2>0.986, P<0.001). The values of b in length-weight relationship in males (3.1495), females (3.1843) and for all specimens (3.2137) indicated isometric growth. Mean relative condition factor for male, female and all specimens were 1.003, 1.004 and 1.008 respectively. The result of LWR could be used for fishery managers to approve appropriate regulations for sustainable fishery management. Few studies have been conducted on these parameters of pike and this is the first report on LLRs, LWR and Kn of pike from Iranian waters

Qualitative assessment of Caspian kutum (Rutilus frisii kutum Kamensky 1901) stocks in Iranian waters of the Caspian Sea (1991-2011)

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

The study of feeding, reproduction and biological parameters of kilka fishes in the Iranian waters of the Caspian Sea

The overfishing and changing environmental following the introduction of the comb jelly Mnemiopsis leidyi in the Caspian Sea, the population structure has a strong influence on kilka fishes in the Caspian Sea and therefore to in this investigation which had been done in commercial catch regions (where discharged theirs catch) in three ports Babolsar, Amirabad (in mazandaran) and Anzali (in Guilan), stimated catch and catch per unit effort, the age structur of catch, length- weight relationship, von Bertalanffy growth parameters, condition factor, sex ratios, maturity stags, spawning and feeding. The result shown that catch of kilka in Iranian coastal in 2012 decreased from 24080 ton to 22696 ton in 2013. But CPUE increased was 2.7 ton (Vessel ×Night) and there was no significant changes. Common kilka was the predominant all months of the year, 98.1 and 98.9 percent in 2012 and 2013 respectively. The mean length was 104.4±10.5 and 101.6±11.2 at the same time and range length 92/ 5 – 117/5 mm were the dominant population(about 75%). Relative abundance of fish less than 77.5 mm and more than 127.5 mm is very low. Age abundance during this period have not been substantially changed and always fishes with 3 and 4 year olds had the highest frequency73.6 and 73.5 percent respectively. The parameters of the Von Bertalanffy growth curve were (8.141) 048.1 for common kilka. The instantaneous coefficient of natural mortality (M) was 0.506 yr-1. The instantaneous coefficient of fihing mortality and total mortality were 0.694 yr-1 and 1.2 yr^-1 , respectively. The exploitation rate of common kilka varied during 2012-2013 between 0.41-0.50. The mean condition factor 1.41±0.14 (n=5801) and 1.38±0.16 (n=6754) at the same time respectively. According to statistical analysis Anova oneway were a significant difference between condition factor at the same time . Main prey common kilka was Acartia tonsa accounting for over 80%. It seems Common kilka due to a decrease in the frequency of other zooplankton species depend more than ever on Acartia tonsa and this species is probably a concentration of prey for Common kilka

Growth performance and age composition of Salmo trutta caspius in Iranian part of Caspian Sea

The aim of this project is to study the growth and age structure in the Caspian trout, comparison with other coldwater species and check the trend of these parameters in recent years. This study was conducted during 2013 till 2015. Totally, 43 specimens for back calculation and 101 specimens for biometrical study of the Caspian trout have been caught in two month period. Biometric parameters such as length, weight and age of the fish were recorded. Base on Back calculation method in 1393, the average length of fish at ages 1, 2 and 3 years old were 18.98 ± 3.5, 30.5 ± 7.24 and 41.7 ± 9.1 cm. So these age groups are under the adult age and don’t approaching to near the beach and rivers for spawning behavior. Therefore, these length groups cannot be observed in catch composition. The result showed, the mean of gonad weight in this fish was about 11 percent of total weight and number of eggs per gram of gonad calculated about 10.8 numbers. Minimum age and maximum age of this species determined 4 years and 7 years (mean = 5.6) and the most frequency allocated to 5 age group and the frequency of 6 and 7 years has been remarkable. The average length of salmon was 69.2 ± 6.2 cm (minimum 57 and maximum 81 cm) and the average weight was measured 3323 ± 677 g (2400 to 5600 g) in the catch composition. Growth parameters such as k, L_∞ and ø’ was measured 0.18, 104 cm and 3.289 respectively. The amount of b for relation length and weight was 2.9 which imply negative allometry. L_∞ and growth coefficient (K) on the Caspian trout were acceptable range, that it shows good growth the fish in the sea water. Most of the fishes were catched from Cheshmehkileh River. As at present Shilat uses just the broods of the Tonekaboon region for restocking of this species, we recommend using the broods of the western region separately for rehabilitation of the stocks of this region