The biological parameters and stock assessment of kilka in Iranian waters of the Caspian Sea

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, von Bertalanffy growth parameters, condition factor, sex ratios, spawning, biomass and maximum sustainable yield of common kilka in Iranian waters of the Caspian Sea. The result shown that catch of kilka in Iranian coastal in 2015 increased from 21553 ton to 22428 ton in 2016 and CPUE was 2.6 and 2.7 ton (Vessel ×Night) respectively . Common kilka was the predominant all months of the year about 98 percent. The mean length was 103±9.6 at the same time and range length 92.5–112.5 mm were the dominant population (about 82%). The mean condition factor was 1.38±0.1 . Age abundance during this period have not been substantially changed and always fishes with 3 and 4 year olds had the highest frequency78.5 and 76.8 percent respectively. The parameters of the Von Bertalanffy growth curve were 138[1 exp ] 0.251( 1.124)   t Lt 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 0.753 yr-1 and 1.259 yr-1 , respectively. The exploitation rate of common kilka were 0.60 during 2015-2016. In the years 2014-2015 and 2015-2016, the biomass of common kilka was estimated 86401 and 71671 ton, respectively. In these years, fish of the 2nd and 3rd year of this fish had the highest amount of reserves (respectively 29025 and 24632 ton) and The lowest reserves for 6-year-old fish, respectively, were 772 and 355 tons respectively. The breeders biomass of this species is 37132 and 34390 tons respectively and The ratio of biomass of broodstocks to the whole was 43% and 48% respectively. Acceptable Biological Catch was estimated with a precautionary approach of 18,400 tons. The average catch of this species on the coast of Iran in the last 10 years has been more than 21,000 tons, and in fact, the optimal level of harvesting from the reserves has not been observed. It should be noted that when exploiting a storage facility, excessive harvesting of the harvestable product will lead to the destruction of longterm storage.