Growth and Mortality of Sillago sihama (Forsskål) from Karachi Coast, Pakistan

Abstract

Length frequency data of silver sillago, Sillago sihama (Forsskål) were collected and measured from the fisherman catches using beach seines and handlines, at random, during 2012 from the Karachi coast of Pakistan. In this study, 1846 fish individuals (male and female combined) were collected ranging from 10 to 24 cm with dominant individuals ranged 12 to 16 cm (total length). Weight ranging was measured from 9 to 110 g. The above length-frequency data were analysed for the estimation of growth and mortality parameters. The power coefficient b of length-weight, the relationship was estimated at 2.9177. The estimated von Bertalanffy growth, function parameters of 25.20 cm (L∞) and 1.00 year-1 (K) were calculated by ELEFAN method equipped on FiSAT computer package. With length-converted catch curve analysis, the total mortality rate (Z) and its 95% confidence interval were 2.42 (2.174-2.669) year-1. The natural mortality rate (M) was 1.84 year-1 calculated with Pauly’s equation (the annual average seawater temperature was 27°C). Therefore, the fishing mortality rate was Z-M= 0.5787year-1. The exploitation ratio (E) estimated as F/Z=0.239 which is less than biological reference point (0.5), therefore it indicates that the stock of S. sihama was exploited at managed.