Dietary Proportion of Fish Culture Solids Required by Shellfish to Reduce the Net Organic Load in Open-Water Integrated Multi-Trophic Aquaculture: A Scoping Exercise with Cocultured Atlantic Salmon (Salmo salar) and Blue Mussel (Mytilus edulis)

Abstract

ABSTRACT Integrated multi-trophic aquaculture (IMTA) aims to recapture portions of nutrient waste lost from 1 species as nutritional inputs for another. This process has the potential to augment growth of cocultured species while reducing the nutrient load from an aquaculture site. In several jurisdictions, open-water aquaculture is regulated through measures of benthic hydrogen sulfide concentrations, which is proportional to excess deposition of organic material such as feces and uneaten food. Interception, consumption, and digestion of organic portions from the fed trophic level (e.g., fish) by organic extractive species (e.g., shellfish, deposit feeders) results in “organic stripping,” with less organic material in resulting feces, thereby reducing the net organic load and benthic deposition potential. Shellfish are deployed beside fish cages in some openwater IMTA systems. In addition to the potential consumption of fish culture solids (i.e., feces, feed “fines”), natural particles (i.e., seston) wil...