Stocking Density, Growth and Survival Rate of Post-Settled Juveniles of Holothuria scabra (Jaeger 1833) Reared in an Ocean-Based Floating Hapa

Abstract

Ocean-based nursery system using floating hapa have proved to be the best option for raising early sandfish juveniles. However, the nursery system can be further improved by providing key information that will support their application. The present study provides information on the effect of stocking density on growth and survival of sandfish juveniles reared in floating hapa (1 x 0.5 x 1 m). Three densities were tested, 100, 200 and 400 early juveniles (5 mm; 0.093 g) per hapa net in a randomized set-up. Initial density of 100 and 200 showed significant higher growth rate and final size (0.082–0.074 g/day; 3.76–3.42 g) compared to 400 (0.045 ± 0.002 g/day; 2.11 ± 0.07 g). Moreover, at 100 and 200 densities, > 95% of all juveniles attained release size (2 g) and only 74% for 400 density after 45 days of rearing. Sandfish juveniles showed negative allometric growth and their survival did not display any pattern (100 = 91%; 200 = 35%; 400 = 51.3%). The coefficient of variation for weight of juveniles showed strong positive relationship with initial density (R² = 0.99, p = 0.039) with CV values of (100 = 48.6%; 200 = 49.8%; 400 = 50.1%). It is therefore concluded that, 100 stocking density should be opted for optimum results, however, 200 can also be considered provided that, the survival is improved.  

Keywords: Sea cucumber; Ocean-based Nursery; Stocking density; Survival rate; Growth rate