Integrated multi-trophic aquaculture (IMTA) in marine temperate waters

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Integrated mariculture – A global review
The objectives of the present paper are:
– To review the current status (production systems and scales, environmental,
economic and social benefits, etc.) and future potential of IMTA in regions situated in
temperate marine waters, using the best published and personal contact information
available.
– To outline the requirements for further expansion of IMTA in the world’s marine
temperate waters.
REVIEW OF CURRENT IMTA SYSTEMS
The IMTA concept is extremely flexible. It can be applied to open-water and land-based
systems, and marine and freshwater systems (sometimes then called “aquaponics” or
“partitioned aquaculture”). What is important is that the appropriate organisms are
chosen based on the functions they have in the ecosystem and, moreover, for their
economic value or potential. What is quite remarkable, in fact, is that IMTA is doing
nothing other than recreating a simplified, cultivated ecosystem in balance with its
surroundings instead of introducing a biomass of a certain type expecting this can be
cultivated in isolation of everything else.
Moreover, IMTA goes beyond environmental sustainability; it provides economic
diversification and reduces economic risk when the appropriate species are chosen,
and it increases the acceptability of the overall aquaculture sector by using practices
evaluated as responsible by the industry, the regulators and the general public.
Presently, the most advanced IMTA systems in open marine waters have three
components (fish, suspension feeders such as shellfish, and seaweeds in cages and
rafts), but they are admittedly simplified systems. More advanced systems will have
several other components (e.g. crustaceans in mid-water reefs; deposit feeders such as
sea cucumbers, sea urchins and polychaetes in bottom cages or suspended trays; and
bottom-dwelling fish in bottom cages) for either different or similar functions but for
different size brackets of particles, or selected for their presence at different times of
the year, for example.
North America
Canada
In Canada, aquaculture of salmonids (salmon and trout), groundfish (cod and haddock),
and shellfish (oysters, scallops and mussels) has been ongoing for many years. Canada
produced, in 2004, 96 774 tonnes of salmonids and 37 925 tonnes of shellfish, with
a respective value of US$298 056 000 and US$48 834 000 (Table 1). Most of the
aquaculture systems in Canada are intensive monocultures. The blue mussel (Mytilus
edulis) dominates the shellfish production with 60 percent of the volume, while
oysters (Crassostrea virginica and Crassostrea gigas) make up 33 percent. Seaweeds
(e.g. Laminaria, Saccharina, Alaria, Ascophyllum, Fucus, Furcellaria, Palmaria and
Chondrus), although not cultivated in aquaculture systems, have been harvested as
wild crops. The seaweeds are used primarily as sources of alginates, carrageenans,
agrichemicals (biostimulants and fertilizers), animal feed supplements and ingredients,
edible sea vegetables, nutraceuticals and botanicals for the health and beauty industries
(DFO, 2001; Chopin and Bastarache, 2004). Acadian Seaplants Limited, based in
Dartmouth, Nova Scotia, is a world leader in the development of land-based seawater
tank cultivation of seaweeds (Chondrus crispus) with a unique commercial cultivation
operation in Charlesville, Nova Scotia.
Within the past eight years, IMTA projects have been developed on both the
Atlantic and Pacific coasts. On the Atlantic coast, in the Bay of Fundy, a project
integrating the culture of salmon (Salmo salar), blue mussels (Mytilus edulis) and
kelps (Saccharina latissima, previously described as Laminaria saccharina, and Alaria
esculenta) has been ongoing since 2001 (Chopin and Robinson, 2004) and the results