Implementation of a microalgae and live prey production system (daphnia) to improve African catfish Clarias gariepinus fry growth

Abstract

Fish farming in Senegal encounters many difficulties, especially during the first life stages, which are more demanding for food and more sensitive to variations in the physicochemical parameters. Most of the species of aquaculture interest have offspring whose size at birth is very small, thus requiring a particular rich food adapted to the size of the mouth (e.g. live preys which are very rich in nutritive reserves). The objective of this study was to set up a production system of live prey, daphnia for the feeding of fish fry. It consisted of culturing microalgae that were used to fed daphnia reared to fed the fry of the African catfish, Clarias gariepinus. The temperature and dissolved oxygen content in the culture and rearing media were monitored throughout the experiment. The results on species identification showed that the cultured microalgae and reared daphnia species are Microcystis sp and Daphnia magna, respectively. Analyses of algal biomass and daphnia abundance show an increase in these parameters with time. Temperature variations do not affect algal biomass, daphnia abundance and fry growth. On the other hand, a decrease in dissolved oxygen content below a certain threshold (6mg/l) leads to a decrease in algal biomass and daphnia abundance. Among the three feeding rates 1.5g, 3g, 4.5g (the equivalent of 0.5L, 1L, and 1.5L of microalgae, respectively) that were used to feed daphnia, the feeding rate of 3g of biomass corresponding to 1L is more adequate as it gave the best production. The comparison of the effects of the types of feed shows that live daphnia give better growths of C. gariepinus fry than the artificial feed, which may be due to their adequate size and nutrient richness. Thus, this study contributes to the establishment of live prey production systems to boost local aquaculture development and demonstrates the importance of daphnia for the feeding of early fish life stages.