Impact of Stocking Size on Growth and Production Performance of Pearlspot (Etroplus suratensis) in Cage Culture: A Comparative analysis of Different Size Groups

Initial stocking size plays a crucial role in cage aquaculture, directly influencing fish growth, production, and economic returns. In this study, the impact of varying initial stocking sizes on the growth and yield of pearlspot (Etroplus suratensis) was evaluated in Enamavu Lake, located in the Thrissur district of Kerala, India. Pearlspot were stocked at a density of 1,500 fish per cage (4×4 m)across three size groups—T1 (0.39 ± 0.004 g), T2 (3.77 ± 0.87 g), and T3 (11.65 ± 2.11 g)—with three replicates per treatment. The trial was conducted over 332 days, during which the fish were fed commercial floating pellets containing 44% crude protein, administered twice daily at 5% of body weight. The results showed that initial stocking size significantly affected growth performance, feed conversion ratio (FCR), total biomass, and net profit (p < 0.05). Although T1 exhibited the highest specific growth rate (2.32 ± 0.03 %/day), a strong positive correlation (r = 0.992) was observed between initial stocking size and total yield. Mean yields were 2.83 ± 0.04 kg/m3 for T1, 3.90 ± 0.031 kg/m3 for T2, and 5.06 ± 0.01 kg/m3 for T3, with statistically significant differences among treatments (p < 0.05). Despite T3 producing the highest biomass, the benefit-cost ratio was significantly higher for T2 (1.56 ± 0.00) and T1 (1.51 ± 0.01) compared to T3 (1.28 ± 0.01), indicating that T2 resulted in the greatest net profit (p < 0.05). These findings suggest that stocking medium-sized fingerlings (T2) is the best in terms of biological performance and economic viability for the commercial cage culture ofpearlspot in Kerala.