Comparative Studies of Spawning Potentials in Female African Bonytongue Heterotis niloticus (Curvier 1829) between Cross River and Great Kwa River, Nigeria

Abstract

The spawning potentials of Heterotis niloticus from Great Kwa River and Cross River was compared in a twelve-month study. Forty-nine female H. niloticus was sampled from Cross River and thirty four from Great Kwa River from January to December 2014.  Gonadosomatic index (GSI), fecundity and histological examinations were investigated in the Institute of Oceanography laboratory. Each month of this study recorded at least one female specimen with eggs at different stages of development. In Cross River, the months of August and September recorded one hundred per cent female with eggs, while Great Kwa River exhibited such performance in July, an indication of spawning activities by the fish. Cross River had a major GSI peak in July with a minor one in August, but Great Kwa River did not exhibit any significant GSI peak throughout the study, and no significant difference in GSI between the rivers when compared with T-test (0.22; P>0.05). There was a significant difference (0.02, P<0.05) in fecundity of H. niloticus between the population in Cross River and Great Kwa River. Regression analysis of fecundity and body weight showed a positive correlation (P<0.05)(r=0.3686). Histological changes in the gonad of the fish showed no disparity between the rivers. H. niloticus has the ability to spawn all year round, but in the Cross River, the fish has high reproductive potentials than those in the Great Kwa River.