Performances Et Contraintes Des Élevages Intensifs Du Cladocère Daphnia Magna Straus, Utilisations Des Biomasses Produites

Abstract

[Daphnia magna is easy to bread and allows important productions. Experiments in the Museum d'Histoire naturelle (Paris), in 2 m3 tanks, showed productions between 200 and 400 g m3 week-1 in summer conditions (temperatures: 18-25°C). Daphnia received as food microalgae cultivated on pig manure. In winter, Daphnia productions remained poor (<30 g m3 week-1) in spite of microalgae provided in large quantities. Because of its important capacity of filtration, Daphnia magna has a purifying effect on its environment which causes an increase of water transparency, very favourable to macrophytic algae. These algae can develop in mass, making collecting of Daphnia difficult. The algae can be eliminated by an application of simazine (2 g m3). Daphnia magna is very sensitive to inorganic pollutants but supports easily organic substances. This organism can absorb dissolved organic substances, bacteria, and chiefly very important quantities of microalgae proliferating on domestic or urban wastes and intensive breeding manures. Daphnia is very rich in proteins (to 60% of dry weight) and its amino acid composition is favourable to nutritional requirements of young fish. They can be used living (for example as food for young pike) but it is also possible to use different ways of conservation: desiccation, freezing, silage, with preservatives. So, many utilizations are possible: feeding aquarium fish, distribution to young fish eating no living food (Cyprinids). They can also to be added to artificial food for aquatic and terrestrial animals. Lastly, extraction of chitin of the carapace can be envisaged for many industrial purposes., Daphnia magna is easy to bread and allows important productions. Experiments in the Museum d'Histoire naturelle (Paris), in 2 m3 tanks, showed productions between 200 and 400 g m3 week-1 in summer conditions (temperatures: 18-25°C). Daphnia received as food microalgae cultivated on pig manure. In winter, Daphnia productions remained poor (<30 g m3 week-1) in spite of microalgae provided in large quantities. Because of its important capacity of filtration, Daphnia magna has a purifying effect on its environment which causes an increase of water transparency, very favourable to macrophytic algae. These algae can develop in mass, making collecting of Daphnia difficult. The algae can be eliminated by an application of simazine (2 g m3). Daphnia magna is very sensitive to inorganic pollutants but supports easily organic substances. This organism can absorb dissolved organic substances, bacteria, and chiefly very important quantities of microalgae proliferating on domestic or urban wastes and intensive breeding manures. Daphnia is very rich in proteins (to 60% of dry weight) and its amino acid composition is favourable to nutritional requirements of young fish. They can be used living (for example as food for young pike) but it is also possible to use different ways of conservation: desiccation, freezing, silage, with preservatives. So, many utilizations are possible: feeding aquarium fish, distribution to young fish eating no living food (Cyprinids). They can also to be added to artificial food for aquatic and terrestrial animals. Lastly, extraction of chitin of the carapace can be envisaged for many industrial purposes.]