Selection of locally available diets for rearing Scylla paramamosain megalopa to first crablet stage

The aim of this research was to investigate the efficacy of seven different diets including live Acetes (LA), minced shrimp meat (MSM), locally formulated feed (LFF), a commercial feed (CF), and three combination diets of LA with MSM (LA + MSM), LFF (LA + LFF) and CF (LA + CF) on the nursery production of mud crab (Scylla paramamosain) crablets. To avoid the influence of cannibalism on the test diets, these diets were simultaneously tested under individual and communal culture conditions. For individuals, individual one-day-old megalopa was reared in 0.5 L plastic beakers. For commune, 250 megalopae were reared in earthen dugout holes. The average survival (mean ± SD) of first crablet stage was 93.6 ± 5.56 in individual culture system and 67.0 ± 14.95 in communal culture system, however, the gap survival between individual and communal culture within the different diets was similar, indicating that cannibalism didn't effect on results of evaluating test diets. The LA resulted in higher survival of crablets than MSM, LFF and CF, but not significantly different to combination diets. All megalopa fed exclusively LA or LA + CF synchronously moulted into the crablet stage one day earlier than those fed MSM, LFF, CF, LA + MSM and LA + LFF. However, none of the test diets influenced the growth of the first crablets. The present research indicates that all the test diets are appropriate to rear megalopa into crablet stage as reflected by successful moults and high survival of first crablets, in which LA is the optimal diet that resulted in increased survival, synchronous moulting, and reduced duration period required for metamorphosis. •The effect of cannibalism did not influence on results of evaluating the test diets.•All the test diets can be alternatives to expensive feed for raising megalopa to the crablet stage.•The combination of live Acetes with other test diets did not show any additional benefits.•Live Acetes resulted in enhanced survival, synchronous moulting, and decreased development time.