Evaluation of Different Larval Feeds for Survival and Development of Early Stage Mud Crab (Scylla olivacea)

Abstract

               The effects of early feeds and feeding regimes on survival and development of mud crab (Scylla olivacea) larvae were studied in two experimental phases ; phase 1 from zoea 1 to zoea 5 and phase 2 from megalopa to the first crab stage. In the first phase trial, the treatments were characterized by feeding regimes of two types of feeds of which the first feed was applied from outset zoea 1 and later when entering zoea 2, the first feed was partially substituted by the second feed. The treatments of aboved regimes were as followed: 1. rotifer and artemia 2. rotifer and frozen copepod 3. artemia and rotifer 4. artemia and frozen copepod 5. microencapsulated feed and artemia and 6. microencapsulated feed and frozen copepod. It was shown that the survival rate of zoea when developed till zoea 5 were 13.89, 4.00, 2.50, 10.33, 0.11 and 0.00% for treatments 1 to 6, respectively. The survival rates for treatments 1 and 4 were higher (P<0.05) than those of the other treatments. The average time for the development of zoea into zoea 5 were less (P<0.05) in treatments 1 and 4 which were 20.67 and 21.67 days, respectively.

                The second phase aimed to study the effects of feed on the development of megalopa to the first crab stage. The experiment was randomized into five treatments for the following feeds: 1. artemia 2. chopped mussel 3. artemia and larval shrimp feed 4. artemia and chopped mussel 5. larval shrimp feed and chopped mussel. Survival rates of megalopa developed to the first crab stage were 75.00, 16.44, 63.89, 58.33 and 47.22% for treatments 1 to 5, respectively. There were no significant differences (P>0.05) in survival rates for treatments 1, 3 and 4 and these were higher (P<0.05) than that of treatment 2. The average development time of megalopa to the first crab stage in treatments 1 to 5 were 12.05, 15.22, 10.77, 12.15 and 10.99 days, respectively, which were not significantly different (P>0.05) among treatments.