Production of exotic fish and Brazilian hybrids in similar conditions: Are there considerable differences of environmental performance?

In developing countries and tropical regions, earthen ponds have become an alternative for farming fish inland. Farmers usually restrict diet to compound feed, which is a relevant source of environmental impact. In the conditions described above, the motivation of this study was to evaluate the environmental impact of fish farming developed with different species. We evaluated systems producing the exotic Nile Tilapia (Oreochromis niloticus), the local hybrid Patinga (Piaractus mesopotamicus x Piaractus brachypomus) and local hybrid Surubim (Pseudoplatystoma sp. x Leiarius marmoratus). Species were bred separately, in the same farm and in similar conditions. The study was also inspired by the opportunity to properly pinpointing the most relevant reasons to explain variability of environmental performance among fish species. For this goal, we used the Life Cycle Assessment (LCA) technique, preparing our inventory by collecting realistic data, on farm, and restricting the evaluation from cradle-to-farmgate. Distinctive to many simulations in literature, we properly determined the nitrogen (N) and phosphorus (P) content of fish and feed in a bromatology Lab. To produce 1 ton of live weight, the exotic Tilapia performed considerably better than the Surubim in all impact categories evaluated. Compared to Patinga, Tilapia performed considerably better in two impact categories: water dependence and land occupation. No considerable differences were observed between the two local hybrids. For the global warming potential, the acidification potential and the eutrophication potential, feed production and fish farming were the stages that contributed the most. In general, the source of protein in feed was the predominant source of environmental impact. Indeed, terrestrial animal co-products have more embodied resources in their tissue, due to diversifying and reasonably low feed conversion rates among fish species. However, the discussion spans towards trade-offs and the puzzling situation for decision making. This includes tunneling waste for aquaculture feed instead of dumping it on the landfill, or increasing the demand for terrestrial or marine ingredients by overbalancing in some direction. At the same time, the pathway towards sustainability of fish farming systems relies on finding alternative ingredients and managing genetic resource in order to improve feed conversion rates, empower and speed up production. For sure, these tasks demand efforts to meet the nutrient requirements of fish and offer feed with suitable composition. Overall, the methodology presented in this study can be used to compare and demystify environmental performances among local and exotic genetic resources.