Gonadosomatic Index, Fecundity and Egg Size of Auchenoglanis occidentalis (Cuvier and Valenciennes) in River Rima, North-Western Nigeria

Abstract

Study was carried out on Auchenoglanis occidentalis from River Rima, North-Western Nigeria to provide information on gonadosomatic index, fecundity and egg size. Eight hundred samples of the fish (398 females, 399 males and 3 with unidentified sexes were examined between November 2005 and December 2008. GSI, fecundity and diameter of the eggs were analysed. Linear regression analysis was used to determine the
relationship between GSI, fecundity and egg size with total length (TL), total weight (TW), gonad weight (GW) and gonad maturation stages (MS). Six stages of gonad maturation were established. Mean gonadosomatic index (GSI) for female and males were 2.01±2.75SD and 0.17±0.32SD, respectively. It varied with sex, size class and gonad maturation stage, and exhibited significant (P<0.05) correlation with fish TL, TW and MS in females but not in males. Mean fecundity was 2834.45±2530.87SD and it correlated significantly (P<0.05) with GW, MS and inversely with egg diameter but not with TL and TW. Mean egg size was 1.31±0.33mm. It correlated significantly (P<0.05) with TL, TW and GW but not with MS. Egg size distribution was bimodal, with different sizes of egg in ovaries indicating multiple spawning. This study provided baseline information on some aspects of reproduction which is important in the management of A. occidentalis in River Rima.

Keywords: Gonadosomatic index, fecundity, egg size, A. occidentalis