Effects of stocking density on survival, food intake and growth of giant gourami (Osphronemus goramy) larvae reared in a recirculating aquaculture system

International audienceThe influence of stocking density on survival, food intake, and larval growth was assessed in giant gourami (Osphronemus goramy) larvae reared in an indoor recirculating aquaculture system. Larvae aged eight days post-hatching were arbitrarily divided into six stocking density treatments (A: 0.6, B: 1.2, C: 2.4, D: 4.8, E: 9.6, F: 19.2 individuals L−1; four replicates per treatment) and reared for three weeks. Tubifex worms, used as food, were kept continuously available for larvae. Samples of larvae were collected at days 0, 7, 14 and 21. Performance indicators - including survival rate (%), food intake (% and g ind−1), total length (cm), body weight (g), specific growth rate (g day−1), biomass gain (g L−1), feed conversion ratio (FCR), condition factor (K) and coefficients of variation (%) - were measured. Water quality was checked throughout the experiment and parameters were maintained below critical thresholds for fish. The results showed no effect of stocking density on survival (> 98%) or size heterogeneity, although growth significantly decreased with increasing stocking density. At the end of the 21-day experiment, mean individual body weights were 563.2 ± 64.3, 461.0 ± 28.6, 288.8 ± 19.3, 170.2 ± 13.8, 113.6 ± 6.9 and 81.9 ± 2.3 mg, for groups A, B, C, D, E and F, respectively. Decreased growth may be due to reduction in food intake in larvae stocked at the highest densities. The consequences of intensification of giant gourami larval rearing should be further investigated in the nursery and grow-out phases