Behavioural responses under different feeding methods and light regimes of the African catfish (Clarias gariepinus) juveniles

Little is known about the behaviour of fish under culture conditions. Several factors may have a direct effect on fish behaviour and its variations during the day. This study assessed the effect of feeding method (continuous by self-feeders vs. twice a day hand-feeding), light intensity (15 vs. 150 1x) and photoperiod [continuous light vs. 12 h darkness and 12 h light (12D:12L)] on behaviour of juvenile African Catfish (Clarias gariepinus). Sixteen aquaria, each with 30 fish (average initial weight of 55 g) were used during a 6-week experimental period. Fish behaviour was recorded by direct observation. Fish were more active under hand-feeding regime than under self-feeding. Fish spent more time swimming under continuous light than under a 12D:12L. Furthermore, the time that fish spent swimming was higher at high light intensity (150 1x) than under low light intensity (15 1x). Aggression was affected by photoperiod and light intensity. Continuous light resulted in 41.6% more scars and wounds than the 1213:12L photoperiod, while high light intensity resulted in 2.46 times more scars and wounds than low light intensity. Fish that spent more time swimming and browsing were more aggressive, and they had more scars and wounds on the body. Fish under the hand-feeding method showed a higher activity during the morning compared to the afternoon. Fish also showed a higher activity before each meal (morning and afternoon meals) than afterwards. These activities were more evident during the mornings. The current study demonstrated that for juveniles of the African catfish, swimming activity and agonistic behaviour are strongly affected by husbandry conditions. (C) 2004 Elsevier B.V. All rights reserved.