Incorporation of salmon fish feed and feces components in mussels (Mytilus edulis): Implications for integrated multi-trophic aquaculture in cool-temperate North Atlantic waters

Abstract

The incorporation of salmon fish feed and feces components in the digestive gland, mantle, and gill tissue of blue mussels (Mytilus edulis), and associated growth in shell length and soft tissue dry weight, were studied in a 28day laboratory experiment. Mussels were fed mixed rations of either salmon fish feed and Rhodomonas baltica, salmon feces and R. baltica or mono rations of either a full or half ration of R. baltica. Feed rations were designed to supply a particulate organic carbon ration equal to ~5% of soft tissue carbon content ind−1day−1.Significant changes in the fatty acid composition, which appointed that of the food profiles, were evident in the digestive gland and gill tissue (p<0.05), whereas no changes were found in mantle tissue. For digestive gland data, a principal component analysis particularly identified the contribution of 18:1 (n−9), 18:3 (n−3), 18:2 (n−6) and 20:1 (n−9) and as being the single fatty acids most responsible for the difference between the various diets.A significant growth in length was found for mussels fed fish feed and R. baltica (p<0.05), but not for mussels fed feces and R. baltica. The dry weight was significantly higher for mussels fed the full diet with R. baltica compared to the other diets, and significantly lower for mussels fed feces and R. baltica than fish feed and R. baltica at the end of the experiment (p<0.05).A more pronounced incorporation of salmon feed compared to salmon feces components in mussel tissues suggested that mussels will utilize fish feed more efficiently than feces particles in an integrated aquaculture with salmon.