Determination of Asymptotic Growth in Progenies of Crosses Between Clarias gariepinus and Heterobranchus longifilis and Attenuation of Intra-cohort Cannibalism

Abstract

Using weight as a measure of size in cannibalistic species can be misleading. This research determined the growth pattern, cannibalism and heterosis of crosses between two African catfishes Clarias gariepinus (Cl) and Heterobranchus longifilis (Ht). Fry were reared communally for Cl×Cl, Cl×Ht, Ht×Cl and Ht×Ht for 14 days before triplicates of 100 fry were randomly stocked in concrete ponds. The length of the samples was taken weekly, and growth shooters were sorted out using the criteria of cut-off length earlier proposed by the authors. The Gompertz model successfully converged for the growth modelling of three crosses: Cl×Cl, Cl×Ht and Ht×Cl with asymptotic values of 40.44 mm, 59.42 mm, 57.27 mm. In contrast, the cross HtxHt converged using the monomolecular growth model with an asymptotic length of 72.09 mm. Type I and type II cannibalism were observed with a greater influence of H. longifilis. Absolute growth rate (AGR) was highest in Ht×Cl (1.52 mm.day-1) progeny and lowest in Ht×Ht (1.02 mm.day-1). There was positive heterosis for length and AGR with negative heterosis for survival (–8.93%) and sorting (–1.86%). There was positive heterosis for cannibalism. The study revealed the maximum length attainable for offspring of these crosses and sorting effectiveness/criteria.