Genetic parameters and genotype-environment interaction for growth traits of North African catfish, Clarias gariepinus (Burchell, 1822)

Abstract

Aquaculture of North African catfish, Clarias gariepinus (Burchell, 1822) (Cg) has been widely practiced with global production sharply increasing by almost three folds in the past decade (FAO, 2018). Despite its advantageous growth rate and disease resistance, the genetic potential has not been fully exploited. Therefore, this research was conducted to estimate genetic parameters of growth traits of Cg in Thailand and to estimate the interaction of genetics and environment when it is cultured in different pond-types. Three genetically distinct stocks of Cg were crossed following a factorial mating design (a male mated with 2–3 females, each from different strains) which resulted in a total of 90 full-sib and 29 half-sib families. The fry were separately reared in two replicate hapas until 98 days after hatching (DAH) and were then tagged using elastomers and communally reared in two environments, namely earthen ponds and circular polyethylene (PE) tanks, each with two replicates. Body measurements were made when the fish reached market size (BW~300 g, 138 DAH) and genetic analyses were performed using an animal model. The results showed significant differences in body size and growth rate among families. Heritability estimates for the growth traits (body weight, BW; total length, TL; and standard length, STL) were high (0.49–0.51) at 98 DAH, while heritability for condition factor (K) was 0.06 ± 0.01. At 138 DAH, the heritability estimates for growth traits were slightly lower than at 98 DAH. Heritability (h2) estimated for the two environments were equal for body length, and slightly different for BW (PE-tanks: h2BW = 0.35 ± 0.07; h2TL = 0.34 ± 0.07, h2STL = 0.29 ± 0.07; earthen ponds: h2BW = 0.25 ± 0.06; h2TL = 0.34 ± 0.07, and h2STL = 0.29 ± 0.07). Heritability for K was higher in the PE-tanks (h2K = 0.31 ± 0.07) than in the earthen ponds (h2K = 0.11 ± 0.04). Genetic correlation of the same traits between the two environments was high for all traits and hence suggested no G × E interaction for growth traits in Cg. The results suggested that selective breeding of this population would give substantial selection response, and the improved strain derived from the PE-tank environment would perform similarly in earthen ponds.