Ocean nursery systems for scaling up juvenile sandfish (Holothuria scabra) production: ensuring opportunities for small fishers

Cost-effective production of juveniles to release size (>3 g) is a primary objective in the culture of Holothuria scabra. Ocean nursery systems were developed to help overcome the space limitations of a small hatchery setup and shorten the rearing period in the hatchery. The growth and survival of first-stage juveniles (4–10 mm) in two ocean nursery systems—floating hapas and bottom-set hapa cages—were compared with those reared in hapa nets in a marine pond. Juveniles reared in these nursery systems were healthy and in good condition. Survival was not substantially different in hapa nets in marine ponds and floating hapas. However, growth in pond hapa nets was higher than in the two ocean nursery systems. Nonetheless, the estimated cost of producing juveniles in the floating hapa system is considerably cheaper compared with those reared in the other systems. Moreover, local community partners easily maintained the floating hapas and reared the juveniles to release size. Further, the effects of sand conditioning on juvenile quality were also investigated. The growth of sand-conditioned juveniles was higher than unconditioned ones in hatchery tanks, and more conditioned juveniles buried within the first hour of release in the field. From floating hapas, juveniles can be conditioned in sea pens for at least 1 week, or reared to bigger sizes for 1–2 months (>20 g) prior to release. However, whether this intermediate rearing procedure will be practical with large numbers of juveniles needs to be considered. Results show that ocean nursery systems are simple and viable alternative systems for scaling up juvenile sandfish production compared with hapas in marine ponds, which might not be available and accessible to small fishers.