Effect of feeding with different types of nutrients on intensive culture of the water flea, daphnia magna straus, 1820

Abstract

These experiments have been done aimed to prove that the water flea, Daphnia magna, can be intensively cultivated and grown on a variety of the food industry residues as well as algal powder under controlled culture conditions with no deficiencies. In mass culture experiments, population densities of 7000 to 10,000 individual per liter were obtained within 6 weeks with average yields ranged between 400 to 450 g/m3/week, depending on the food type. Selective harvesting of the larger individuals (more than 1mm) at weekly scale has a beneficial return on the Daphnia culture as it gives the opportunity for smaller individuals to grow and stimulates them to reproduce. The average conversion ratio from different food used ranged from 2.27 to 2.55. The best food conversion ratio was obtained from soybean while wheat bran was the worst. The current study concluded that Daphnia magna is considered as one of the most important zooplankton species that can be relied upon to feed fish larvae, due to its high content of animal protein that reached 47.7%, as well as the caloric value of 333.7 cal. (i.e. 1397.14 j/g dry weight). Also, these organisms have a rich source of various necessary vitamins and some vital antioxidants such as tannic acid and β-carotene in good proportions. On the other hand, analyzing the bacterial content of these organisms revealed that they are free from most common pathogenic bacteria such as Escherichia coli, Salmonella, and Clostridium in present culture conditions. In addition, the aflatoxin levels are very low and below the internationally permitted rates.