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Mussels and Kelp Help Salmon Farmers Reduce Pollution

by Ellen Hardy
03 July 2008, at 1:00am

CANADA - Mussels and kelp are being grown alongside salmon pens in Canada's Bay of Fundy in an attempt to reduce the level of pollution caused by net-pen aquaculture, according to the conservation group SeaWeb.

The technique, known as integrated multitrophic aquaculture (IMTA), is being put into practice by Cooke Aquaculture and scientists from the University of New Brunswick and Canada's Department of Fisheries and Oceans.

Net-pen farming can lead to pollution of coastal waters as organic waste and nutrients seep from pens into the surrounding environment.

Sediment, including fish excrement and uneaten food, can settle on the seabed and smother vulnerable habitats. High levels of dissolved nutrients in the water surrounding fish pens can promote the growth of nuisance species, including algae harmful to humans and other animals.

IMTA works by recreating a portion of a natural food web or ecosystem.

Mussels and kelp grow by filtering and absorbing organic materiel and nutrients from the water, and so reduce the level of pollution associated with adjacent salmon pens.

The growth rate of these commercially important species is enhanced when grown alongside fish pens, so fish farmers' profits could also increase.

Most research to date has focused on mussels and kelp, however there is potential for a number of other species to be produced in this way, including sea urchins, sea cucumbers and scallops.

As public awareness of the potentially harmful consequences of aquaculture increases, IMTA offers a way for fish farms to improve their environmental credentials and profit margins simultaneously.

Ellen Hardy