REARING PERFORMANCE OF FLOATING HAPA BAG NETS FOR JUVENILE SANDFISH Holothuria scabra IN CENTRAL PHILIPPINES  

Roselyn D. Noran*, Jon P. Altamirano, and Charlemagne P. Recente
 
Southeast Asian Fisheries Development Center
Aquaculture Department (SEAFDEC/AQD)
Tigbauan, Iloilo, Philippines
roselyn.noran@seafdec.org.ph  

Global sea cucumber populations are declining because of overfishing. Hatchery production of sea cucumbers, particularly of the tropical sandfish Holothuria scabra have been progressing in the past decade but the corresponding improvements in nursery and grow-out technology have been slow. Various nursery systems for rearing of sandfish has been developed and modified through the years to optimize growth performance and survivorship. Sea-based nurseries, particularly the floating hapa nursery systems have shown great production potential and practical applications especially in the Philippines and the West Pacific regions. To evaluate rearing performance of floating hapa bag net for juvenile sandfish, various experiments were conducted by SEAFDEC/AQD in Iloilo and Guimaras, central Philippines. Performance indicators such as growth, survival, and optimal stocking densities were assessed using 40-45 d old post-metamorphic juveniles (~5mm, ~0.03g) produced in the hatchery. Floating hapa bag nets were made from fine-mesh (1 mm) PE net fabricated to a dimension of 1×2×1 m (Length×Width×Depth) and fitted on floating PVC pipes to be suspended from the water surface (Fig. 1). Experiments were conducted at the Igang Marine Station (IMS) of SEAFDEC/AQD located in Guimaras Island, central Philippines.

The general trend in survival and growth of sandfish juveniles with different initial stocking densities after a 30-d culture duration is presented in Table 1. During a good season with no heavy rains, high survival (>80%) and good growth (>2 g) can be achieved at densities of <700 individuals per hapa without supplemental feeding. Sandfish only fed on naturally accumulating algal biofilm on the nets. Results indicated that growth and survival is significantly influenced by stocking density, where average growth rates increase as density decreases. However, other variables such as food composition and abundance, seasonality and competition/predation are among the challenges that must be considered for future studies. With an understanding of these site-specific factors, nursery rearing can be programmed to optimize production potential of sandfish juveniles in sea-based floating hapas.