A Review of the Biotic Factors Militating Against Successful African Catfish (Clarias gariepinus Burchell) Larviculture In Nigeria
Victor F. Olaleye
Department of Zoology, Obafemi Awolowo University, Ile-Ife, Nigeria.
Accepted on June 24, 2005.
The African catfish (Clarias gariepinus Burchell) with its unique adaptive traits is one of the most successful fish species for culture in Africa. Despite its popularity and ability to spawn under controlled conditions with hormonal induction, the seasonality of spawning in the fish imposes considerable strain on the Nigerian commercial fingerling producers limited by unsophisticated hatcheries. On most Nigerian catfish farms, the established hatchery protocols are rarely observed leading to low egg hatchability and poor larval survival. Ignorance of the requisite hatchery protocols lead to the production of catfish juveniles lacking the expected vigour. Under optimal conditions after the yolk-sac absorption period, larval rearing requires feeding live-organism during the first four days before introduction of an exogenous feed. Imported cysts of Artemia nauplii which is usually the first choice of feed for the new catfish hatchlings is expensive and not affordable to an average Nigerian fish farmer who instead utilize mixed zooplanktonic assemblages as first choice live-feed usually for a maximum of 14 days. Mixed zooplanktonic assemblages mainly Moina spp, Brachionus spp and Daphnia spp which are produced in organically fertilized nursery ponds are instead used to wean the Clarias hatchlings in most farms. In most commercial fingerling production operations, economics and nursing space dictates the duration of the primary nursing period. Survival of the hatchlings have been found to be dependent on biotic factors such as availability of live food organisms, predation, cannibalism, nursing space and competition for food, all of which are dependent on the levels of abiotic factors such as water temperature, turbidity, levels of dissolved oxygen and ammonia.