Integrated Multi-Trophic Aquaculture (IMTA)

Media reports and programs have raised the prospect of IMTA as a new approach to cleaning up open net-cage salmon farming.

IMTA integrates raising plants and/or animals (which are usually lower on the food chain), with salmon in the same enclosure in an attempt to reduce organic waste. Waste is mostly fish feces, uneaten food pellets and the dust or “fines” from food pellets broken during shipping and handling that are released into the water from open net-cage salmon farms. Species like seaweed, mussels and other invertebrates are able to take up some of these organic wastes and therefore potentially reduce their accumulation.

IMTA is an interesting effort at lessening some waste-related impacts of salmon farming. However, IMTA fails to address some of the key environmental impacts like sea lice and disease that are causing so much trouble for wild salmon, nor does it stop escapes of farmed fish into the wild.

As such, IMTA farms do not automatically rank as more sustainable than other types of open net-cage salmon farming and do not qualify for preferential treatment by consumers or seafood companies. To date, there has been no formal and publicly transparent assessment of the overall sustainability of these farms. The few efforts to award “eco-certification” labels to companies that have some IMTA farms have been industry-developed programs that do not have transparent criteria or participation from independent science or conservation stakeholders. Such certifications simply don’t qualify as credible.

Currently, the major user of IMTA in Canada, Cooke Aquaculture, only uses this method on less than 1% of their total farmed salmon production. This small innovation does not warrant claims of sustainability being broadly applied to Cooke’s farmed salmon products.

While we are supportive of efforts to find better ways to farm salmon, CAAR’s position is that only the separation of farmed and wild fish through some form of closed containment can sufficiently reduce the risk to wild salmon and the environment. IMTA may have a role to play in closed containment projects that recycle wastes into salable products, but IMTA use in open net-cages does not make open net-cage farming any more appropriate or sustainable.