Poulations dynamics and stock assessment of common kilka (Clupeonella cultriventris caspia ) in Iranian waters of the Caspian Sea

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 ۱۹۹۵-۲۰۰۴. For most years during this ۱۰-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¥=۱۳۲mm, K=۰.۲۵۹/yr, t۰=-۱.۲۸۵/yr. The instantaneous coefficient of natural mortality was estimated at ۰.۵۰۶/yr and the instantaneous coefficient of fishing mortality varied during the ۱۰-year period between ۰.۱۲۵/yr to ۱.۴۸۷/yr. Biomass of the common kilka increased from about ۱۶,۰۰۰mt in ۱۹۹۵ to more than ۴۱,۰۰۰mt in year of ۲۰۰۲. 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.

Keywords:

Clupeonella cultriventris caspia , Growth , Maturity stages , Stock assessment , Caspian Sea