Live food dependence and the lack of suitable artificial diets are major constraints for the expansion of the larviculture in many fish species. The low digestibility and nutritional quality of artificial diets are factors that might explain their failure as starter food for fish. In this thesis, physiological aspects related to the capacity for digestion of food by fish larvae were studied. In addition, the protein quality in decapsulated cysts and nauplii of Artemia was evaluated, and the feasibility of using cysts as protein source in microdiets for fish larvae was studied. African catfish Clarias gariepinus was the experimental species.
The results indicate that catfish larvae have the capacity to digest Artemia. The exogenous supply of digestive enzymes has a small contribution to the overall larval digestion. The protein in Artemia is mainly constituted by small size proteins, which might be more easily digested by the fish larvae than the proteins in artificial diets. It is suggested that the structure and size of the proteins in the fish food might have a very important role for its digestibility. In vitro studies on the protein digestibility of Artemia decapsulated cysts and nauplii, and of microbound diets made of decapsulated cysts revealed a higher digestibility of those diets compared to commercial diets. The use of decapsulated cyst of Artemia as protein source in microbound diets improved their performance as starter diet for fish larvae.