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Dr Thierry Chopin Integrated Multi-Trophic Aquaculture (IMTA): A responsible approach to farming our waters
n September 1995, I gave a presentation entitled “Mixed, integrated, poly-, or multi-level aquaculture - whatever you call it, it is time to put seaweeds around your cages!” at a conference in St Andrews, New Brunswick. I could see a number of faces in the room saying, “What is this guy talking about?!” The period 1995-2000 was spent “preaching in the desert” for what was just “integrated aquaculture”. We wanted to differentiate our practice from monoculture. The obvious term was polyculture; however, cultivating three species of fish together, while being polyculture, does not address the problems of co-cultivating three fed species together. In March 2004, at a workshop in Saint John, New Brunswick, we gave a name to what we were doing. I came up with “Integrated Aquaculture” and Jack Taylor with “Multi-Trophic Aquaculture”. By combining the two, “Integrated Multi-Trophic Aquaculture” or “IMTA” was born, and in the 14 years since, more than 1,300 publications referring to IMTA have been published worldwide. With IMTA, farmers cultivate species from different trophic levels, with complementary ecosystem functions, in proximity. They combine fed species (e.g. fish) with extractive species (e.g. seaweeds, aquatic plants, shellfish and other invertebrates) to take advantage of synergistic interactions among them, while biomitigation operates within a circular economy approach (nutrients are no longer considered wastes or by-products of one species, but co-products for the others). The aim is to ecologically engineer a new ERA of aquaculture systems (Ecosystem Responsible Aquaculture) for increased environmental sustainability (ecosystem services and green technologies for improved ecosystem health), economic stability (improved output, lower costs, product diversification, risk reduction and job creation in coastal and rural communities), and societal acceptability (better management practices, improved regulatory governance, nutrient trading credit incentives and appreciation of differentiated and safe products).
IMTA is like the music of JS Bach: A central theme with many variations
The scope of the IMTA concept is extremely broad and flexible; moreover, it is ever evolving. IMTA can be applied worldwide to open-water or land-based systems, marine or freshwater systems, and temperate or tropical systems. IMTA was never conceived to be only the cultivation of salmon, kelps and blue mussels, in temperate waters, and within the limits of existing finfish aquaculture sites. That is how we started in Canada, in order to be able to conduct experiments at sea, within
the limitations of the regulations presently in place, rather than extrapolating from small tank experiments in laboratory conditions, which may not reflect what really occurs in the environment. This is only one of the variations and the IMTA concept can be extended to very large ecosystems. Other variations include: integrated agriculture aquaculture (IAA), integrated fisheries aquaculture (IFA), integrated silviculture (mangrove) aquaculture (ISiA), integrated green water aquaculture (IGWA), integrated biofloc aquaculture (IBFA), integrated temporal aquaculture (ITA), integrated sequential aquaculture [ISA, also called partitioned aquaculture (PA), or fractionated aquaculture (FA)], sustainable/sustained ecological aquaculture (SEA), aquaponics or freshwater IMTA (FIMTA), integrated peri-urban aquaculture (IPUA), integrated ocean ranching (IOR), and integrated food and renewable energy parks (IFREP).
Need for an Integrated Coastal Area Management (ICAM) strategy
A major rethinking is needed regarding the functioning of an “aquaculture farm” and innovative practices need to be developed. It would be a complete illusion to think that an aquaculture farm only functions within the limits of a few buoys, arbitrarily placed in the water by humans, or a few GPS coordinates on a map. Therefore, its management should be based on an Integrated Coastal Area Management (ICAM) strategy, considering different spatial and temporal recapturing strategies to recover the different types of nutrients. Large particulate organic nutrients should be managed within the farm. Small particulate organic nutrients should be managed within the farm or around its immediate vicinity. Dissolved inorganic nutrients should be managed at the ICAM scale, either when produced directly or after re-mineralization of the organic matter. The “Integrated” in IMTA should be understood as cultivation in proximity, not considering absolute distances, but rather connectivity in terms of ecosystemic functionalities at the ICAM scale (in particular, nutrients and energy hydrodynamics). This means that the different components of an IMTA system do not, necessarily, have to be right at the same location (e.g. within relatively small finfish sites), but that entire bays/coastal areas/regions (including marine protected areas) could be the units of IMTA management. Nothing says that only one company should be in charge, producing all the IMTA components. There may need to be several companies coordinating their activities within the ICAM. “Multi-Trophic” refers to the incorporation of species from different trophic or nutritional levels in the same system. It is not enough to consider multiple species (like in polyculture); they have to be at multiple trophic levels, based on their complementary functions in the ecosystem. Species selection, combinations and proportions will be highly variable depending on the local conditions and biodiversity. The cocultured species should be more than just biofilters; they should also be harvestable crops of economic value or potential. To bestow full value to IMTA, extractive species will need to be valued for not only their biomass and food trading values, but also for the ecosystem services and the increase in consumer trust and societal/political license to operate they provide (again within a circular economy approach).
There is no ultimate IMTA system and that is why IMTA cannot be reduced to a short bureaucratic definition
There is no ultimate IMTA system to feed the world. Different climatic, environmental, biological, physical, chemical, economic, historical, societal, political and governance conditions, prevailing in the parts of the world where they operate, will lead to different choices in the design of the best suited IMTA systems.
16 | October 2018 - International Aquafeed