Survey on population structure of bigeye kilka Clupeonella grimmi Kessler, 1877 in Mazandaran Province coasts

The aim of the present study is surveying on the population structure of bigeye kilka (Clupeonella grimmi Kessler, 1877) in the southern Caspian Sea in Mazandaran Province coasts. In this study which was conducted during 2010, 1043 samples were fortnightly provided from Babolsar fishing harbor in Mazandaran province. Length, weight, sexuality and age of samples were determined. Age was determined using sagitta otoliths. The results were compared with previous years. The growth parameters were calculated as (L∞=149.7mm, k=0.32 yr-1, t0=-1.20 yr) for females and (L∞=136.5mm, k=0.65yr-1, t0=-0.24yr) for males. Length-weight relationship in females was W FL 3.043 = 0.0000006 (R2 =0.813) and in males was W FL 3.079 = 0.000006 (R2 =0.834) which growth pattern in both sexes was positive allometric. Bigeye kilka population was constituted of 6 age groups, including 2-7 years. Mean age of females and males were 4.09±1.25 and 3.61±1.45 years, respectively. In females, 4 years old fish were dominant with 33.34 percent relative abundance. In males, 3 years old fish were dominant with 47.45 percent relative abundance. Male: female sex ratio was 0.656: 1 and females were dominant. Results showed that in recent years, bigeye kilka population has been older and its length and weight has increased. According to the biological parameters and comparing with the previous years, bigeye kilka has not been very affected by the Caspian Sea pelagic changes, due to inhabiting in deep regions.