Integration of Fish, Snail and Water Spinach with Macrobrachium rosenbergii: An Approach of Integrated Multi-Trophic Prawn Aquaculture in Southwest Bangladesh

Abstract

This study evaluated the production performance and profitability of an integrated multi-trophic aquaculture (IMTA) system by incorporating Indian major carp (Labeo rohita), small indigenous fish species (SIS) (Amblypharyngodon mola), snails (Pila globosa) and the floating vegetable water spinach (Ipomoea aquatica) into traditional freshwater prawn (Macrobrachium rosenbergii) ponds. Fifteen earthen ponds of 60 m2 were randomly allocated to five treatments: T1 - prawn and rohu (finfish), T2 - prawn, rohu and mola, T3 - prawn, rohu, mola and snail, T4 - prawn, rohu, mola, snail and water spinach. A control was maintained, stocked exclusively with prawns. The stocking densities of the species were 2, 0.1, 2 and 0.25 m−2 for prawns, rohu, mola and snails, respectively. In addition, 20 water-spinach sprouts were planted in a floating bed of 0.14 m2. The culture period of the experiment was 7 months. The average weight throughout the experiment, final weight, weight gain and gross production of prawns were significantly higher in T4 compared to the control group (p < 0.05). A similar level of gross prawn production was observed in T3, which also showed significantly higher survival and gross production of rohu compared to the other groups. In addition, the production of waterspinach and snails made a surplus profit to T4. The gross return, net profit and benefit cost ratio was significantly higher in T4, followed by T3 and T2, compared to T1 and control. The introduction of water spinach significantly reduced the concentrations of ammonia (0.02 ± 0.01mgL−1 ), nitrite (0.05 ± 0.03mgL−1 ), nitrate (0.27 ± 0.01mgL−1 ), phosphate (0.03 ± 0.00mgL−1 ) and free CO2 (7.52 ± 5.25) in pond water compared to other groups. This reduction is attributed to the biological purification of organic and inorganic waste, enhancing the overall utilization of the trophic layers. Therefore, the application of IMTA is crucial for sustainable prawn farming to ensure food and nutritional safety.