Dr. Richard Newton and Prof. Dave Little published a paperin the upcoming special edition "Challenges and best practice in LCA's of seafood and other aquatic products" of the International Journal of Life Cycle Assessment (https://link.springer.com/article/10.1007/s11367-017-1386-8). Thispaper mapped the environmental impact of producing farmed salmon throughout the value chain up to primary processing. Over 90% of the impacts are at the feed production stage to grow and process ingredients.
As around 75% of feed ingredients for Scottish farmed salmon are sourced from overseas, many of the impacts also occurred overseas. Noticeably there were large impacts on land and water in South America and central Europe, although impacts from transporting ingredients were comparatively low. We concluded that companies which are promoting "local" production as being more environmentally benign have a duty to be transparent about the wider impacts of production.