Economic, environmental and nutritional benefits of transitioning from monoculture systems to integrated multi-trophic aquaculture in Kenya

Integrated Multi-Trophic Aquaculture (IMTA) offers a circular economy-aligned alternative to intensive monoculture that, in most cases, addresses issues like effluent discharge and excessive feed use, contingent on the appropriate species combinations. Despite its potential, adoption remains limited due to high costs and system complexity. This paper assesses the economic, environmental, and nutritional benefits of transitioning from monoculture finfish production to IMTA in Kenya. A system dynamics model simulated six systems: three species combination in IMTA systems—(i) cage-based rabbitfish with oyster and seaweed; (ii) pond-based Nile tilapia and shrimp with sea cucumber; and (iii) pen-based rabbitfish with seaweed and sea cucumber—and their monoculture equivalents. The model was parameterized with data from pilot trials and secondary sources. Findings show IMTA significantly improves profitability. Pen-based IMTA achieved the highest returns, generating $7.88 per $1 invested (communal model), followed by $7.74 (fully privatized). Among IMTA systems, the cage-based IMTA required the highest unit investment ($91.24–$91.50/m³) and emitted the lowest total GHGs (13,022.98 kg CO₂e), while pond-based IMTA had the highest total emissions (124,198.3 kg CO₂e). Nutritionally, pen-based IMTA offered the highest ash and polyunsaturated fatty acids; pond and cage systems had the highest protein and potassium content, respectively. While IMTA enhances overall returns, trade-offs exist between profit and environmental impact. Communal models yielded slightly higher but statistically insignificant profits compared to privatized ones. Strategic species selection is critical to balance economic gains with sustainability. Policymakers should consider incentivizing low-emission aquaculture through support for IMTA technologies and environmentally conscious production models.