Enhancement of protein, lipid and fatty acids in copepod, Oithona rigida for the improvement of growth, development and survival of early‐stage mud crab larvae ( Scylla olivacea )

Abstract

The copepod Oithona rigida can be used as a natural feed in rearing larvae of the mud crab Syclla olivacea. However, copepod is not readily obtainable due to their characteristics as seasonal zooplankton, causing limitation in using copepods. The objective of this study was to evaluate the nutrient transfer of enriched O. rigida in improving the growth development and survival of early‐stage mud crab (Scylla olivacea). The effects of different feeding regimes on the survival and development of S. olivacea larvae were studied in two phases of the crab larval development: Phase 1 (zoea 1 to zoea 2 stage) and Phase 2 (zoea 5 to megalopa stage). The feeding regimes were T1: O. rigida enriched with rice bran, T2: O. rigida enriched with Nannochloropsis oceanica, T3: O. rigida enriched with a mixture of rice bran and N. oceanica, and T4: Artemia. The results showed that rice bran (66.83 ± 2.25% protein and 21.98 ± 1.41% lipid) and N. oceanica (72.08 ± 2.02% protein and 18.09 ± 1.18% lipid) additives produced the best outcomes in terms of protein content and lipid content of O. rigida. A mixture of rice bran and N. oceanica (41.62%) as enrichment also improved the polyunsaturated fatty acids (PUFAs) content of O. rigida as compared with a mono diet applied such as rice bran (28.16%) and N. oceanica (31.35%). The average survival rate of S. olivacea from zoea 1 until megalopa shows that T3 (20.20 ± 1.97%) was higher than T1 (13.87 ± 0.90%), T2 (12.47 ± 1.14%) or T4 (3.13 ± 1.29%). In conclusion, improving the survival rate of crab larvae in commercial hatcheries by using precise early‐stage foods is fundamental to enhancing the seed production technology of mud crabs.