Tank-Based Nursery Production of the Sea Cucumber Holothuria scabra in Various Seaweed Feed Regimens

Abstract

This study explored the feasibility of Laurencia papillosa, Sargassum spp, and Gracilaria bailinae crude extracts as feeds for the juvenile sea cucumber Holothuria scabra in a tank-based system. Post-metamorphic juveniles (~1 mm) were harvested from larval tanks and were reared until the late juvenile stage in indoor tank systems at 300 ind./tank stocking density for 45 days. Growth and survival rates of H. scabra juveniles were monitored to assess the performance of each seaweed treatment. L. papillosa consistently yielded the best growth (SGR: 7.63-11.32%.d-1) and highest survival rates (54.6–56.8%) of H. scabra juveniles. The performance of L. papillosa did not differ from that of Sargassum spp., while G. bailinae yielded poor growth (SGR of 5.01–9.38%.d-1) and low survivorship of juveniles (8.77–19.77%). Growth and survival rates were similar between fresh and dried seaweeds (p>0.05), suggesting dried seaweeds' applicability as feeds for juvenile H. scabra. Moreover, increased feed rations resulted in better growth of juveniles, but survival rates among feed rations (4.5, 6.0, 7.5, and 9.0 L.d-1) did not differ significantly (p>0.05). The monthly mean water temperature ranged from 26.6°C to 28.8°C, salinity of 33.2–35.1 ppt, dissolved oxygen of 6.1–8.3 mg/L, and pH of 8.1–8.3. High yields of sea cucumber juveniles were observed during the dry season, while low survival rates (<20%) were observed during wet months. The success of this study could set forth the application of tank-based nursery systems for H. scabra, especially during the season of high rainfall and extreme weather conditions that heavily affects cage rearing in the open-sea setting.