Abstract
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).The main objectives of the present study were to estimate of catch and catch per unit effort, biomass and maximum sustainable yield of common kilka in Iranian waters of the Caspian Sea. The catch of kilka in Iranian coastal in 2020 from 20053 tonnes decreased to 19108 tonnes in 2022 and CPUE was 2.3 and 2.4 ton (Vessel ×Night) respectively . Common kilka was the predominant¬ all months of the year about 96.7 and 94.4 percent respectively .
The mean length was 98.9±11.9 mm, the minimum and maximum fork lengths were 62.5 - 137.5 mm in 2020 (n=4236), 102.4± 10.2 mm, the minimum and maximum fork lengths were 62/5- 137/5 mm in 2021( n=5522) and 100±1/10/4 mm, the minimum and maximum fork lengths were 137.5-52.5 mm in 2022 (n= 6777). The mean condition factors were 1.57±0.11 , 1.67±0.16 and 1.63±0.19 in 2020, 2021 and 2022. Age abundance during this period have not been substantially changed and always fishes with 3 and 4 year olds had the highest frequency¬ 78.9 , 78 and 89.4 percent respectively. The parameters of the Von Bertalanffy growth curve¬ were¬ for¬ common kilka.¬
In these years, the biomass of common kilka were estimated 92653 and 78135.3 and 95555.3 ton, respectively, for 3- year- old fish had the highest amount of reserves 31615.1 , 22672.6 and 27656.8 ton and the lowest reserves for 6-year-old fish, were 611.1 and 943.8 and 723.7 tons respectively. The breeders biomass of this species were 44277.6 and 41606.5 and 43504.3 tons and the ratio of biomass of broodstocks to the whole was 47.8 , 53.2 and 45.5 percent respectively. The instantaneous coefficient of natural mortality (M) was 0.514 yr-1. The instantaneous coefficient of fihing mortality (F) and total mortality (Z) were 0.632 yr-1 and 1.146 yr-1 , respectively. The instantaneous coefficient of fihing mortality (F) were 0.641 , 0.631 and 0.624 yr-1 in 2020, 2021 and 2022 respectively. The exploitation rates ( E) of common kilka were 0.552 , 0.553 and 0.549 1 in 2020, 2021 and 2022 respectively. The Acceptable Biological Catch was estimated between 17000-18000 tonnes and with a very cautious approach, less the 17000 tons were estimated. The average catch of this species on the coast of Iran in the last 10 years has been more than 21000 tons,It is suggested that in the coming year, with the cooperation of more fishermen and the care of regional managers, effective measures should be taken in order to realize the optimal annual harvest with a precautionary approach.
Keywords : Kilka fishes, Biological Index, Biomass, Stocks Assessment, Caspian Sea