Strategies for improving survivorship of hatchery-reared juvenile Holothuria scabra in community-managed sea cucumber farms

Community-based aquaculture of the sea cucumber Holothuria scabra offers a potentially profitable and ecologically sustainable complementary livelihood activity for coastal communities in the tropical Indo-Pacific region where the species is widespread. However, H. scabra aquaculture remains a relatively novel practice. Early efforts to farm the species as an alternative to fishing in coastal communities have commonly faced several practical challenges that have so far prevented the commercial success of the enterprise, such as unacceptably high levels of juvenile mortality during – and even more after – the transfer of juveniles from hatchery to sea pens. This study assesses the impact on survivorship of hatchery-reared juvenile H. scabra of a series of technical improvements to community-managed sea cucumber farming practices in southern Madagascar. The improvements included structural modifications to farming pens, better maintenance of the pens and active management regimes that included intensive culling of predatory crabs. The impacts of these improvements on the survival of H. scabra juveniles are analysed over three periods spanning pre- and post-implementation phases of these strategies. Results show that, prior to improvement, average juvenile survivorship three months after transfer from hatchery to sea pens was only 40.2%; a level too low to enable the farming system to cover its costs or reach profitability. The technical improvements and active management strategies introduced increased survivorship to 76.6%, a significant jump in productivity that is expected to have significant positive economic implications for the profitability of the enterprise in coastal communities. Our findings indicate that, within community-based farming settings, technical solutions must be coupled with active management to maximise the survivorship of juveniles in the first months of the farming cycle following transfer from the hatchery.