Possible use of Brachionus plicatilis (O.F. Müller) as food for freshwater cyprinid larvae

Abstract The use of the euryhaline rotifer Brachionus plicatilis as food in raising freshwater fish larvae was tested with the Japanese ornamental carp, koi ( Cyprinus carpio ) and a breed of bait fish ( Carassius sp.). Providing rotifers in addition to granulated food improved significantly the growth rate of fish larvae and also, in the case of ornamental koi, their survival. Growth rate in terms of increase in length was found to fit a simple empirical formula similar to a power growth curve. The curve fits results obtained with bait fish ( R 2 =0.85) better than those with Japanese koi ( R 2 =0.76). The coefficients of growth for each treatment ( β i ) were used to evaluate the contribution of rotifers to the larval growth. The improvement in growth was found to correlate with the quantity of rotifers, being higher with the larger quantity offered (2400 larva −1 day −1 ). In bait larvae, results obtained from measuring length were supported in weight measurements taken on day 8, but not by those recorded on day 11. Between day 8 and day 11, these larvae were fed on granulated food only. Preliminary results indicate that yeast-fed rotifers were superior to algae-fed ones when supplied to bait fish larvae in equal quantities, in addition to granulated food.