Dietary protein requirement of purple mud crab, Scylla tranquebarica during the megalopa-crab instar stages.

Mud crab has great demand globally, leading to extensive research that focuses on enhancing the crab survival in hatcheries. This study aimed to evaluate the optimal protein requirement of mud crabs during the transition from megalopa to the early instar stage. The megalopae were cultured in triplicate black containers (n = 30) and fed one of the five formulated diets containing 40%, 45%, 50%, 55%, or 60% dietary protein for 14 days. The growth, survival, and larval stage composition were evaluated on days 7 and 14. The percentage of crab instars 1 (C1) on day 7 (20.07 ± 3.43% to 41.63 ± 5.77%) and C2 on day 14 (47.37 ± 2.35% to 57.96 ± 5.67%) revealed an increasing trend from the 40% to 55% protein level treatments, however, the percentage decreased in the 60% treatment. Growth performance exhibited a similar increasing trend from 40% to 55%, declining at 60%. Enhanced growth with 55% protein was supported by the lowest food conversion ratio (P < 0.05) and highest protein and lipid efficiency ratio (P < 0.05). However, the results did not differ significantly with the group fed with 50% protein. A second-order polynomial regression on the growth performance suggested that 51.3% is required for best growth during the transition of megalopa larvae to the early instar stage. [ABSTRACT FROM AUTHOR]