Improvement in laboratory research: Effects of stocking density, variation and sample size on outcomes of growth studies with shrimp

A series of laboratory-based growth trials were carried out in semi-closed recirculation system with juvenile Pacific white shrimp Litopenaeus vannamei. The effect of stocking density, initial size variation and replication was evaluated. Trial 1 was conducted for 42 days with different stocking densities (28, 56, 83, 111, 139, 194 and 250 shrimp/m2) to determine the effect of stocking density on performances of shrimp. Trial 2 was conducted for 56 days (2 × 3 factorial design) to test the effect of stocking density (30 and 60 shrimp/m2) and coefficient of variation (CV) at stocking (8%, 15% and 32%) on performances of shrimp. In third trial, data from 15 replicates were randomly sampled to create data sets with varying levels of replications. Significantly reduced growth and survival were noted when increasing the stocking density of shrimp, while the opposite was noted in FCR of shrimp. No significant effect of initial size variation of shrimp was noted on size variation of shrimp at harvest in both stocking densities tested. No interaction was noted between stocking densities and initial CV of shrimp on determining the size variability of shrimp at harvest. In terms of replicate size, a clear improvement in power and reduction in between sample variation was noted as the replication increased, hence suggested that up to 6 replicates are appropriate for a clear water shrimp nutritional study.