Polyculture potentials of Galda (Macrobrachium rosenbergii) with Heteropneustes fossilis and Clarias batrachus in South-western coastal ghers of Bangladesh

Abstract

Prawn (Macrobrachium rosenbergii) culture is socially more acceptable, technically and economically viable and sustainable. The freshwater catfishes Heteropneustes fossilis (shing) and Clarias batrachus (magur) adapt well to hypoxic water bodies and high stocking densities as well. So, shing and magur may be a good candidate to culture with prawn in ponds/ghers to save the farmers from losing their investment in case of shrimp mortality and getting additional income from fish. With this view, this study was conducted to evaluate the feasibility of polyculture with three treatments each with three replications. Stocking density of shing was variable i.e., 200nos/decimal in T₁, 300nos/decimal in T₂ and 400 nos/decimal in T₃. On the other hand, stocking density of magur and prawn juveniles was 50 and 30 nos/decimal respectably for all treatments. The experimental ghers were treated with salt (NaCl) (150g/decimal), potasium permanganate (5g/decimal) along with lime (125 kg/ha). After stocking fish were fed using floating nursery feed containing 32%, protein and 7% lipid at the rate of 10-2% for shing and magur nursing, floating oil coated grower feed (27% protein and 6% lipid) at the rate of 6-2% for shing and magur grow out and prawn grower (30% protein and 7% lipid) at the rate of 6-2.5% of estimated fish and prawn biomass. At least 10% of stocked catfish and galda were sampled fortnightly using cast net. Physico-chemical parameters of the experimental ghers water were monitored at weekly. After six months of culture the highest growth performance (47.0 g) and survival (19.94%) for shing obtained from T₃. Whereas the average growth of shing was recorded 37.02 and 41.14g; growth of magur 99.21g and 99.51g and growth of galda 69.74 and 70.19 for Treatment T₁ and T₂ respectively. Except ammonia and iron content the other observed parameters of ghers water found congenial for fish health. The value of Benefit-Cost Ratio (BCR) was 1.4 that seems to be profitable and feasible of this polyculture practice.