Transitioning to low-carbon aquaculture for sustainable production of giant freshwater prawns (Macrobrachium rosenbergii) requires precise quantification of in-pond greenhouse gas (GHG) emissions and the adoption of mitigation strategies that maintain profitability. This study conducted a field experiment in the coastal region of southern Bangladesh, assessing seasonal and diurnal variations in CO₂, CH₄, and N₂O fluxes across six systems: non-aquaculture ponds, prawn monoculture, and prawn polycultures incorporating carps, aquatic plants, or snails, alongside an integrated multitrophic aquaculture (IMTA) setup.
Mean GHG emissions were 278 kg CO₂e/ha per cycle in non-aquaculture ponds and 577 kg CO₂e/ha per cycle in prawn polyculture. Among the systems, prawn monoculture exhibited the highest emission intensities per unit of food (1.194 kg CO₂e/kg), protein (0.597 kg CO₂e/100 g), and economic value (45.31 g CO₂e/USD). Conversely, IMTA reduced emission intensities by roughly 40% compared to monoculture and by 20–25% relative to polyculture, while achieving the highest economic return (18,825 USD/ha) and the lowest carbon footprint per dollar earned (24.03 g CO₂e/USD).
Generalized additive model (GAM) analysis identified prawn biomass as the primary determinant of GHG emissions, explaining 74% of the total variation. The inclusion of snails and water spinach in the IMTA system contributed to emission mitigation through the utilization of organic waste, nutrient recycling, CO₂ uptake, and oxygen generation. Collectively, these findings highlight IMTA as a promising cultivation strategy that enhances productivity, minimizes emissions, and improves profitability. This integrative approach offers a scalable solution for advancing low-carbon, nutrient-efficient, and economically viable prawn aquaculture in coastal ecosystems.