Size Differentiation of Fingerlings of Two African Catfishes: Clarias gariepinus and Heterobranchus longifilis and Their Cross Breeds

Abstract: Size heterogeneity in the African catfish is a major problem in successful mass production of fry in the hatchery. This paper outlines the genetic aspects of size heterogeneity in pure line and crossbred African catfish. Hatchery propagation of C. gariepinus (Cl) and H. longifilis (Ht) as well as the reciprocal cross to obtain Cl X Cl, Ht X Ht, Ht X Cl and Cl X Ht. Triplicate batches of 100, 15-day old hatchlings were selected and stocked in plastic tanks with static water culture system and constant aeration. The term growth shooters was used to describe individuals with total length that is approximately greater than the sum of the current week's mean length and the difference between the current week's mean length and the preceding week's mean length. Other parameters estimated include the ratio of growth shooters, their percentage occurrence, survival rate of the fish stocked and skewness (Sk) of length. Temporal variation in growth shooter to non-growth shooter ratio was only significant in the second week of culture (p<0.05). Body length skewness was high for Ht x Cl (Sk=1.450) at the start of the trial while others were moderate. Final body length was approximately symmetric in Cl x Cl (Sk=0.230) and Cl x Ht (Sk=–0.510) with a moderate skew for the Ht x Ht (Sk=0.750) and Ht x Cl (Sk=–0.840) crosses. There is therefore a maternal influence on body length heterogeneity in H. longifilis.