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NSERC Canadian Integrated Multi-Trophic Aquaculture Network

Background The IMTA concept - Fulfilling aquaculture’s growth potential requires responsible technologies and practices. Sustainable aquaculture should be ecologically efficient, environmentally benign, product-diversified, profitable and societally beneficial.

Integrated Multi-Trophic Aquaculture (IMTA) has the potential to achieve these objectives by cultivating, in proximity, species from different trophic levels, and complementary ecosystem functions, in a way that allows one species’ uneaten feed and wastes/nutrients/by-products to be recaptured and converted into fertilizer, feed and energy for the other crops, and to take advantage of synergistic interactions between species while biomitigation takes place (partial removal of nutrients and CO2, and supplying of oxygen). Farmers combine fed aquaculture (e.g. finfish or shrimps fed sustainable commercial diets) with extractive aquaculture, which utilize the inorganic (e.g. seaweeds or other aquatic vegetation) and organic (e.g. suspension- and deposit-feeders) excess nutrients from fed aquaculture for their growth. In this way, all the cultivation components have an economic value, as well as a key role in the services and recycling processes of the engineered ecosystem. The aim is to ecologically engineer balanced systems for environmental sustainability (biomitigative services for improved ecosystem health), economic stability (improved output, lower costs, product diversification, risk reduction and job creation in disadvantaged communities) and societal acceptability (better management practices, improved regulatory governance and appreciation of differentiated and safe products). In this way, some of the externalities of fed monoculture are internalized, hence increasing the overall sustainability, profitability and resilience of aquaculture farms. The economic values of the environmental/societal services of extractive species will have to be recognized and accounted for in the evaluation of the true value of these IMTA components. This would create economic incentives to encourage aquaculturists to further develop and implement IMTA. Seaweeds and invertebrates produced in IMTA systems should be considered as candidates for nutrient/carbon trading credits (NTC and CTC) within the broader context of ecosystem goods and services. Long-term planning/zoning promoting biomitigative solutions, such as IMTA, should become an integral part of coastal regulatory and management frameworks.