Tropicultura (Jan 2008)
Hatchability of African Catfish Clarias gariepinus Eggs in Hapas and in Basins: a Diagnostic Study of Frequent Inhibition by Rainfall and Water Stagnation
Abstract
To diagnose inhibition of egg hatchability by rainfall and water stagnation, some incubating eggs were protected against the physical impact of raindrops, some were subjected to various turbidity levels and others, to various incubation densities (number of eggs/litre of water) in flowing vs. stagnant water. Data analyses showed that, unaffected by raindrops (P> 0.05), hatchability was inversely proportional to both turbidity (coefficient= -0.971) and incubation density (coefficient= -0.973). Only the properly constructed ponds (i.e., with elevated and compacted dykes) which do not receive any runoff should therefore be chosen for to hold incubation hapas, and the pond inlets should be turned off during heavy rainfall. Hatchability depression by stagnant water could be forestalled by limiting incubation density to 480 eggs / litre or by partially renewing the incubation water on a daily basis. By so doing, some Cameroon smallholders have successfully engaged in regular on-farm reproduction of Clarias gariepinus.
