Population dynamics and biological characteristics of kilka species (Pisces: Clupeidae) in the southeastern coast of the Caspian Sea

The aim of the present study was to investigate the age structure, length-weight relationship, sex ratio, sexual maturity stages, growth parameters, natural and fishing mortality coefficients of three species of kilka, including common, anchovy and bigeye kilka. The fork engthweight relationship of common, anchovy and bigeye kilka were calculated as W=0.000153 FL^2 . 37 , W=0.000349 FL^2 . 18 and W=0.00160 FL^2 . 97 , respectively. The parameters of the von Bertalanffy growth curve for length were L∞ = 143.5 mm, K = 0.30 yr^-1 and t0 = -1.02 yr for common kilka; L∞ = 151.9 mm, K = 0.28 yr^-1 and to = -1.12 yr for anchovy kilka and L∞ = 148.6 mm, K = 0.46 yr^-1 and to = -0.18 yr for bigeye kilka. The instantaneous coefficient of natural mortality of common, anchovy and bigeye kilka were estimated as 0.671, 0.633 and 0.881 yr^-1, respectively. The current exploitation rates of three species were estimated as 0.55, 0.41 and 0.26 for common, anchovy and bigeye kilka, respectively. The results suggest that common kilka stock is under over-fishing now.