Environmental impacts of plant-based salmonid diets at feed and farm scales

The environmental consequences of replacing fish meal and fish oil with plant-based sources in salmonid feeds were investigated using Life Cycle Assessment (LCA). Two scenarios of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) farming were compared. The first scenario used a Standard Diet (STD) with high levels of fish meal and fish oil, and the second a Low Marine-Fishery-Capture Diet (LFD) in which fish meal and fish oil were replaced by plant protein and oil sources. Environmental impacts assessed were: acidification, eutrophication, climate change, terrestrial ecotoxicity, net primary production use (biotic resource use), water use, land occupation and total cumulative energy demand. The assessment confirmed the substantial contribution of feed to the environmental burdens of fish production and the LFD scenario led to a significant decrease in biotic resource use compared to the STD scenario with the same total energy demand. Environmental impacts of feeds depended highly on the geographic origins of feed ingredients from fishery (e.g., fish oil from Norway or Peru) and from terrestrial agricultural crop species (e.g., palm oil or rapeseed oil). This study demonstrated the importance of a multicriteria method to give stakeholders the most accurate information on the potential consequences of replacing fishery products with plant-based sources in aquafeeds.

► The environmental impact of fish based and plant based aquafeeds was studied. ► We crossed on farm experiments and LCA approaches on salmon and trout production. ► Plant based diets failed to improve the environmental profile of fish farming. ► LCA will permit to optimise the choice of feed ingredients on environmental basis.