BEYOND THE MONOSPECIFIC APPROACH TO ANIMAL AQUACULTURE — THE LIGHT OF INTEGRATED MULTI-TROPHIC AQUACULTURE

The focus of present-day aquaculture is typically monospecific animal culture. Even the development of “alternative” species for aquaculture usually refers to alternative species of fish or shellfish. However, although introducing another species of fish or shellfish may have short-term benefits, rarely does it balance energetically and ecologically in the long term. What is needed is appropriate proportions of different cocultured organisms, performing different processes throughout the day and seasonally. Other than in Asia, the fundamental role and the contribution of seaweeds in coastal waters have frequently been either ignored or misunderstood. Seaweeds are rarely factored into modeling equations of coastal systems. At a time when nutrification of coastal waters is becoming a pressing issue worldwide and the contribution of the inorganic output of aquaculture to regional nutrient loading is becoming more widely recognized, integrating seaweeds, which act as biological nutrient scrubbers, into fish or shellfish aquaculture is a promising, balanced-ecosystem approach. Integrating seaweeds into aquaculture systems provides bioremediation capability, mutual benefits to the co-cultured organisms, and economic diversification of the industry by producing another value-added marine crop. We discuss these concepts and illustrate the benefits of integrated multi-trophic aquaculture (IMTA) using projects that we are conducting in New England, USA, in which the culture of the red alga Porphyra (nori) is integrated with salmonid culture, and in the Maritime Provinces, Canada, in which open-water aquaculture of Chondrus crispus (Irish moss) is conducted in proximity to mussel and oyster aquaculture operations. The aquaculture industry recognizes its need to practice responsible aquaculture by moving in new directions, such as IMTA. This will require wise investment in research and development.