Potentials of integrated multi-trophic aquaculture (IMTA) in freshwater ponds in Bangladesh

An experimental study was carried out for a period of six months to assess the potential of integrated multi-trophic aquaculture (IMTA) in earthen freshwater ponds. Nine earthen ponds (40 m2 each) were randomly assigned to three treatments in triplicate. Carps and stinging catfish; carps, stinging catfish, and snails; and carps, stinging catfish, snails, and water spinach as IMTA, were assigned to T1, T2, and T3, respectively. The stocking densities were: carps: 20,000 fingerlings ha−1 at a ratio of 3: 1: 2: 2 for catla: silver carp: rohu: mrigal; stinging catfish: 24,700 fingerlings ha−1 in cage-in-pond for all treatments; and snails: 62 kg ha−1 in T2 and T3. The carps were fed with supplementary feed, a mixture of rice bran and wheat bran (1: 1) at the rate of 3-5% of fish biomass; the stinging catfish with commercial feed for the first 45 days, and snail-mixed pelleted feed for the rest of the experimental period, at the rate of 5-25% of body weight. The highest survival, particularly of silver carp, mrigal, and stinging catfish was found in T3, i.e., in IMTA ponds. The weight gain of silver carp, rohu, and stinging catfish was the highest in IMTA ponds. The highest yields of the carps and stinging catfish in cage-in-ponds were obtained in IMTA ponds. The production of snails and water spinach in IMTA ponds contributed to the biomitigation process of organic and inorganic waste, keeping the water quality within suitable conditions for fish culture.