EFFECT OF LIVE FEED ON SURVIVAL, GROWTH AND DEVELOPMENT OF MUD CRAB Scylla serrata (FORSKAL, 1775) LARVAE
Scylla serrata is the common mud crab occurring in the estuarine and mangrove areas and is commonly called as "green crab" that prefers to live in low saline waters. This study aimed to assess the growth and survival rate of mud crab (S. serrata) larvae cultured in sea water fed with different micro algae as live feeds. In the present study the growth gain was higher in the crabs offered with enriched Nannochloropsis sp. (3.13%) fed live feeds of Rotifers and Artemia. Five different types of rearing systems using microalgae Nannochloropsis sp.,Isochrysis sp.,Chlorella sp.,Tetraselmis sp. and Dunaliella sp. were maintained for early larval stages to later stages resulted in the best overall performance of the Mudcrab larvae. The crab stocking density (80 no's/l) and rotifer (15-30no's/ml) and Artemia density (10no's/ml) were observed. Rotifers were enriched with micro-algae before being fed to the crab larvae. Enrichment with micro algae species was performed at a density of 300 rotifers/ml. The water in the enrichment tank was maintained 29-300C to avoid exposing the rotifers to thermal shock when they were added to the larval rearing tanks. Before being fed to the larvae, enriched rotifers were rinsed in clean seawater at the same temperature as the crab-rearing tanks. Both newly hatched and enriched Artemia nauplii were used in the experiments of this study. The density of Artemia during enrichment was 200no's/ml. Although results showed it is possible to rear S. serrata larvae through enriched with Nannochloropsis algae to Rotifers and Artemia nauplii exclusively, larval performance was enhanced by the inclusion of rotifers as a first feed. Significant difference in performance was recorded between larvae fed on the five strains of Algae. Larvae fed on enriched with Duneliella sp. (0.21%) in treatments performed poorly, but there were enriched with other algae like Isochrysis sp.(0.95%),Chlorella sp. (2.85%),Tetraselmis sp. (0.42%) strains are performed well .The survival rate was higher in Nannochloropsis sp. fed animals (3.13%) and lowest survival (0.21%) was observed in animals fed with Duneliella sp. The survival rate was reasonable for other strains. But higher survival rate was reported in the animals fed with Nannochloropsis sp. algae may have potential as supplements to live food in the rearing of S. serrata larvae.
