Studies on aspects of the biology of clarias gariepinus and heterobranchus longifilis from river Offin: Towards their culture development in Ghana.

Abstract

This study examined some aspects of the biology of Clarias gariepinus and Heterobranchus longifilis as a contribution towards their culture development in Ghana. Samples of the two fish species were obtained monthly from September 2017 to August 2018 from River Offin at Dunkwa-on-Offin. Physico-chemical parameters of their habitat were measured. Morphometric characteristics, sex, gonads and stomach contents of the fishes were examined in the laboratory. Data were analysed using Minitab 16 and Microsoft Excel 2016. Average temperature, dissolved oxygen, pH and turbidity of the water were recorded as 28.02±1.04 ℃, 2.55±1.52 mg/L, 7.39±0.38 and 715.11±159.09 NTU respectively. C. gariepinus were more abundant and bigger in size than H. longifilis. The two species were below average condition (< 1), however, H. longifilis had a better condition factor of 0.96 relative to 0.75 for C. gariepinus. Length-weight analysis revealed negative allometric growth in both species. Both species explored similar food items with plants dominating their diets. Sex ratio of C. gariepinus was found to be 1:1 and 1.5:1 for H. longifilis. The two species exhibited variable fecundity but C. gariepinus was more fecund (1,750 - 88,930) than H. longifilis (39,170 - 53,891). Fecundity increased with fish size and gonad weight in C. gariepinus but these relationships could not be determined for H. longifilis due to insufficient samples. The rainy season, from April to July marked the major spawning period for C. gariepinus but could extend to August. This is suspected to be same for H. longifilis. Females consistently have higher GSI values than males. H. longifilis should thus be considered for aquaculture in addition to C. gariepinus