Effects of Predator–prey Stocking Ratio on Growth Performance, Feed Utilization, and Production of Asian Seabass (Lates calcarifer)–Nile Tilapia (Oreochromis niloticus) Polyculture in Freshwater Earthen Ponds

Abstract

Freshwater polyculture of carnivorous and herbivorous fish species has emerged as a strategy for improving fish production while reducing feed costs and enhancing resource utilisation. This study evaluated the effects of different Asian seabass (Lates calcarifer)-to-Nile tilapia (Oreochromis niloticus) stocking ratios on water quality, growth performance, feed utilisation, survival, and production under freshwater open-pond conditions in Namakkal District, Tamil Nadu, India. One control treatment (Nile tilapia monoculture) and three predator-to-prey stocking ratios, namely 1:3 (T1), 1:6 (T2), and 1:9 (T3), were evaluated over a 180-day culture period in 0.2-ha earthen ponds. Water-quality parameters remained within the reported acceptable ranges for freshwater aquaculture throughout the experimental period. Among the polyculture treatments, the 1:6 stocking ratio (T2) produced significantly better (P < 0.05) growth performance, with the highest final body weight (1,575 ± 62 g), weight gain (1,560.0 ± 6.2 g fish⁻¹), survival (89.26 ± 3.20%; 1,335 harvested fish), and reported fish production (2,082.6 kg ha⁻¹). Although the lowest feed conversion ratio was observed in T1 (1.31 ± 0.08), the greater biomass production in T2 indicated that an appropriate predator-to-prey balance was important for production under the study conditions. The continuous availability of naturally recruited tilapia fry as live forage supported Asian seabass growth while water quality remained stable. Overall, the 1:6 ratio provided the most favourable combination of growth, survival, and reported production among the tested ratios.