Stocking density affects growth and economics of rearing Amur carp (Cyprinus carpio haematopterus) in floating cage in floodplain wetland of the River Brahmaputra

Abstract

Aim: The study evaluates the effect on growth-and related economic benefits of rearing commercially important food fish, Amur carp, Cyprinus carpio haematopterus fry, in a cage culture system, influenced by stocking densities. Methodology: A 90 day long rearing experiment was conducted in a seasonally opened ecologically sensitive floodplain wetland of the Brahmaputra riverine system at Jaluguti Beel. Floating cages of 6×4×2 m with an effective volume of 40 m-3 were used for rearing the fish. Experimental fish (n = 10800) of initial weight and length 0.17 ± 0.01 g and 1.90 ± 0.05 cm (mean ± SE), respectively, were distributed among four different stocking densities: SD15 (15 fish m-3), SD20 (20 fish m-3), SD25 (25 fish m-3), and SD30 (30 fish m-3) executed in triplicates, following a completely randomized design. Results: The overall growth of fish was significantly (P<0.05) influenced by varied stocking densities. The specific growth rate of reared fish in different stocking densities were 3.43 ± 0.04, 4.20 ± 0.06, 2.96 ± 0.02, and 2.71 ± 0.02, in SD15, SD20, SD25 and SD30, respectively. The biomass (kg per cage) achieved in different stocking densities were 35.90 ± 0.20, 38.50 ± 0.31, 37.20 ± 0.35 and 35.40 ± 0.50. Interpretation: The present findings found an inverse relation between growth performance and stocking density. The study also proposes that rearing of Amur carp fry at a stocking density of 20 fish m-3 in a wetland-based cage aquaculture system yields a better growth response without compromising the benefit cost ratio.