Integrated Multi-Trophic Aquaculture

Integrated Multi-Trophic Aquaculture
Neither monoculture nor polyculture, IMTA is a technique that involves utilizing the waste from a fed species to feed other species kept in the same environment. This creates a balanced ecosystem with enhanced profitability and stability as well as better environmental sustainability. While monoculture is the farming of a single species, and polyculture is the farming of multiple similar species, IMTA incorporates multiple species from different nutritional or "trophic" levels in the same system. For example, a farm could incorporate shrimp, which are fed by the farmers, with seaweed and shellfish, which would make use of any waste nutrients from the shrimp.

Concerns
Some issues have been raised concerning the potential for contaminants being passed from one species to another. However, there has so far been no noticeable levels of heavy metals, pesticides, or other toxins. Worries that mussels grown near salmon farms could have a fishy taste have also been allayed. In fact, their meat yield is significantly higher as a direct result of the increased nutrients from the salmon pens.

Canada
There are two major IMTA projects in Canada.The Bay of Fundy project is a collaborative effort involving industry, academics, and government. It incorporates Atlantic salmon, blue mussels, and kelp working together in a self-contained ecosystem. The Pacific SEA-lab research initiative propogates sablefish, scallops, oysters, blue mussels, urchins, and kelp in a more complex system.

More Info:
http://www.dfo-mpo.gc.ca/aquaculture/sheet_feuillet/polyculture_e.htm
http://www.springerlink.com/content/j416160726015891/
http://www.aquaculture.ca/files/species-multi-trophic.php

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Fish Farming - Misc

Protein
For every kilogram of farmed salmon, it takes between 1.8 to 4.7 kilos of protein pellets. These pellets are made from other fish. In Canada it is illegal to feed fish with food that humans could eat, so the farms ship fish protein in from developing countries with lower food standards. This means that the poorer people there have a harder time getting fish, a vital source of protein for them. This is referred to as "Global Protein Loss."

Parasites
The majority of salmon farmed here in BC are Atlantic salmon. Atlantic salmon are more susceptible to sea lice than Pacific salmon. Normally, they aren't a major problem, as Pacific salmon are able to resist them. However, sea lice thrive in the pens of the less resistant Atlantic salmon, and reproduce in great numbers. These populations then spill into the ocean and cause significant detriment to the wild stocks.
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