Controlled hatchery production of Clarias gariepinus (Burchell 1822): growth and survival of fry at high stocking density

Abstract

. The mean increase in African catfish, Clarias gariepinus (Burchell), weight with time over the entire larval period can be approximated by a cubic or exponential growth model. However, the growth rate indices specific growth rate (k) and the regression coefficient of a cube root transformation of the weight data (b), both vary significantly when measured over successive short intervals from first feeding. In particular, the onset of air breathing is associated with a significant depression in growth rate. The variation in specific growth rate (k) with larval age closely approximates the relationship between mean % increase in body weight per day and larval age; however, the cube root regression coefficient does not share this property. In addition to the effect of larval age the growth rate of African catfish larvae is significantly affected by the initial density at which they are stocked (between 25 and 250 larvae/1) and interactions between age and stocking density. Survival over the larval period, of 80% or more, is apparently unaffected by initial stocking density (between 50 and 250larvae/I); however, the onset of air breathing in particular is associated with an increase in fish deaths.