The rotifer Brachionusplicatilis (O.F. Muller) can be mass cultivated in large quantities and is an important live feed in aquaculture. This rotifer is commonly offered to larvae during the first 7-30 days of exogenous feeding. Variation in prey density affects larval fish feeding rates, rations, activity, evacuation time, growth rates and growth efficiencies. B. plicatilis can be supplied at the food concentrations required for meeting larval metabolic demands and yielding high survival rates. Live food may enhance the digestive processes of larval predators. A large range of genetically distinct B. plicatilis strains with a wide range of body size permit larval rearing of many fish species. Larvae are first fed on a small strain of rotifers, and as larvae increase in size, a larger strain of rotifers is introduced. Rotifers are regarded as living food capsules for transferring nutrients to fish larvae. These nutrients include highly unsaturated fatty acids (mainly 20: 5 n-3 and 22: 6 n-3) essential for survival of marine fish larvae. In addition, rotifers treated with antibiotics may promote higher survival rates. The possibility of preserving live rotifers at low temperatures or through their resting eggs has been investigated.

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Hatching experiments were carried out on a population of Brachionus plicatilis (Dor strain) resting eggs produced in batch laboratory cultures under controlled conditions and then stored for at least one month at 4 ° C in the dark . Light was found to be obligatory for termination of dormancy . Over the temperature range of 10-30 ° C (at 9 .0% 0 salinity), hatching was optimal (40-70%) at 10-15 ° C and decreased linearly with the rise in incubation temperature . Resting eggs incubated over a salinity range of 9-40% 0 (at 15 °C) showed optimal hatching at 16% 0 . Incubation of resting eggs in distilled water permitted normal embryonic development, but neonates died at eclosion . Presence of algae, Chlorella stigmatophora (0 .5 X 106 cell ml -1 ), was found to aid hatching .

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