Use of microbound diets for larval culture of the mud crab, Scylla serrata

Abstract

Routine commercial production of mud crab seed is currently restricted by our limited understanding of the nutritional requirements of Scylla spp. as well as problems commonly associated with the live foods used in mud crab hatcheries. This study investigated the use of microbound diet (MBD) particles as a food source for megalopa and zoea III stage larvae of Scylla serrata. In the first experiment, the nutritional value of four MBD containing dried rotifers, Artemia meal, fish meal or squid meal were evaluated for megalopa reared individually in 250-ml aquaria. Survival of MBD-fed megalopa to the first crab stage ranged from 46.7% to 60.0% with those fed MBD containing fish meal or squid meal showing higher survival than those fed MBD containing Artemia meal or dried rotifers. Larvae fed live Artemia showed the highest survival (80%), while unfed megalopa did not survive to the first crab stage. There were no significant differences (P>0.05) in the average time required for megalopa to reach the first crab stage when fed any of the four MBD. However, shortest development time was recorded for larvae fed live Artemia. In a second experiment, zoea III larvae were cultured communally at a density of 25 larvae l−1 and were fed either 100% live Artemia nauplii, 100% MBD or a 50%:50% combination of MBD and Artemia. Highest survival (66%) and development rate to the zoea IV stage were recorded for larvae fed the 50%:50% combination of MBD and Artemia. Some successful molts were also found among larvae fed MBD exclusively, while total mortality was observed in unfed (control) replicates. The results indicate that the experimental MBD may contain certain beneficial nutrients lacking in Artemia and that co-feeding the MBD with Artemia may enhance larval survival and development. However, they also show that total replacement of live food with the experimental MBD will result in poor survival of zoea III larvae of S. serrata. The results indicate great potential for the use of MBD particles as dietary components for both zoea and megalopa stages of S. serrata. These findings have important implications for the eventual development of cost-effective and reliable hatchery techniques for mud crabs.