The Growth Parameters and Mortalities of Five Species of Synodonits in the Lower River Benue at Makurdi

Abstract

The growth parameters and mortalities of five species of Synodontis in the lower river Benue at Makurdi, Benue State were studied from January,2016 to December, 2018. The asymptotic length (L∞) calculated for the five species ranged from 18.80cm in S.clarias females to 37.04cm in S.membranaceus females. The t0 values were all negative in the combined sexes of S.clarias, S.omias, S.gambiensis and S.membranaceus. In both combined sexes of S.membranaceus and S.schall, the t0 values were positive. The growth rate (K) was low in S.clarias and S.omias (0.301- 0.497, 0.171 - 0.310) respectively and higher in S.membranaceus (0.310 - 0.640), S.schall females (0.430 - 0.580); S.schall males (0.573),S.gambiensis (0.500 - 0.571). Growth performance index (Ø’) was 2.212 in S.gambiensis and 2.946 in S.schall combined. Natural Mortality (M) ranged from 0.5422 in S.omias females to 1.3340 in S.membranaceus males. Fishing Mortality (F) was 0.8214 in S.omias combined and 3.0934 in S.membranaceus females. Total mortality (Z) ranged from 1.52 in S.omias combined to 4.078 in S.membranaceus combined. Mean Exploitation (E) ratios was 0.61 in S.clarias, 0.64 in S.omias, 0.53 in S.gambiences, 0.70 in S.membranaceus, and 0.66 in S.schall. The rate at which these species survived in the River was low (from 0.147, in S.omias combined, to 1.482 in S.membranaceus combined).