Mussel farming production capacity and food web interactions in a mesotrophic environment

Abstract

Low trophic aquaculture (LTA), such as bivalve farming, offers promising avenues to supply sustainable seafood and aquafeed. While bivalve farming usually occurs in highly productive coastal areas which already support numerous human activities and suffer from environmental pressures, numerical tools offer a promising avenue to explore and assess biomass production potential and associated ecosystemic impacts for further development of the industry and prospection of new exploitation sites. In this study, we coupled an ecophysiological model, the dynamic energy budget theory (DEB), with an ecosystem model (NORWECOM.E2E) to simulate blue mussel Mytilus spp. farming production and effects based on the food web in the mesotrophic Hardangerfjord in western Norway. We tested several levels of fjord-scale farming intensity and assessed 2 production purposes: aquafeed and human consumption. Results suggested the Hardangerfjord could host large-scale mussel farming for both purposes. However, large exploitation schemes displayed detrimental effects on individual mussel growth (39% less wet mass after 2 yr) and especially on secondary production (decrease of 33% after 1 yr) due to acute trophic competition. Simulations showed short production cycles for aquafeed were more efficient to exploit primary production, since young and small mussels have lower maintenance and reproduction costs. Dissolved nutrient inputs from salmonid farms had marginal effects on primary production (<2%). However, salmonid and mussel farming activities could compete for the sites with the highest production potential.