Comparison of mudcrab‐based brackishwater polyculture systems with different finfish species combinations in Sundarban, India

To compare production and economic performance of polyculture systems with different species combinations, a 210‐day trial was carried out. In the first combination (T1), milkfish ( Chanos chanos ) and mudcrabs ( Scylla serrata ), and in the second (T2), mullets ( Mugil cephalus , Liza tade and Liza parsia at 0.5:0.5:0.5 ratio) and mudcrabs were stocked keeping fish and mudcrabs at 15,000 numbers per ha, respectively, in both treatments. The finfish were fed floating pellet at 2%–3% and mudcrabs were fed fresh and farm made feed at 5%–8% body weight. Growth parameters of mudcrabs were similar in both T1 (407.64 ± 105.78 g) and T2 (418.89 ± 105.24 g), with no significant differences. Among finfish, M. cephalus attained highest final body weight, 241.55 ± 26.44 g followed by milkfish, 200.46 ± 11.82 g whereas lowest growth noticed in L. parsia (63.69 ± 6.62 g). Length–weight analysis of fish indicated negatively allometric growth ( b  < 3) for grey mullets, parsia and milkfish while L. tade recorded perfect cube low ( b  = 2.99). Male mudcrabs recorded positive allometric ( b  = 3.3) and female crab exhibited negative allometric growth ( b  = 2.68). The total productivity was 4,533 and 3,694 kg/ha with mudcrab contributes 53.69% and 60.56% to the total productivity in T1 and T2 respectively. The economic analysis indicated benefit–cost ratio ( BCR ) of 1.57 and 1.73 in T1 and T2 respectively with 10% and 35% insignificant increase ( p  > 0.05) in BCR and profit per kg, respectively, in T2 compared with T1. The study elucidates polyculture of mudcrabs with finfish can be a taken up as a profitable venture for sustainable diversification of brackishwater farming in Sundarbans.