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Polyculture Pioneers Seeks Sustainable Aquaculture

CANADA - A scientists from the University of Victoria is conducting research to devlop polyculture techniques for a self sufficient, resource recycling, aquaculture system.

Dr. Stephen Cross works at a dedicated aquaculture research and development facility in Kyuquot Sound off northwestern Vancouver Island. It is the first licensed SEAfarm in Canada.

Cross has been specializing in BC aquaculture issues for more than 20 years, and he played a lead role in the development of the SEA-system (Sustainable Ecological Aquaculture) on Vancouver Island. Polyculture—an ancient technique of growing one thing from another—has been used for thousands of years in Asia and is now being applied off our shores by Cross and his team of researchers.


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"The science is getting the correct balance between the number of fish...and the type and quantity of other species"
Dr. Stephen Cross

Sablefish (black cod) are grown at the SEAfarm but are just the first component in the SEA-system: the organic waste from the cod filters down to strategically placed living organisms that capture the waste and use it as a food source. Shellfish (scallops, mussels, oysters, cockles) intercept fine particulates from the cod; sea cucumbers and sea urchins take the settleable organic particles; and kelp (kombu, nori) extracts the dissolved nutrients. Each species is commercially viable in its own right and also serves a unique function within the ecosystem.

Costly closed containment systems have also been developed in an effort to remove these wastes, but in comparison the SEA-system, according to Cross, treats waste as a resource and is designed as an ecological rather than technological-based system.

“The science is getting the correct balance between the number of fish—typically in the thousands in each fish farm—and the type and quantity of other species that will naturally consume and hence mop up any waste,” says Cross.

Cross founded a Coastal Aquaculture Research and Training (CART) multi-disciplinary network at UVic, along with co-director Dr. Mark Flaherty, a UVic geographer and expert on aquaculture’s impacts upon governance and community issues in tropical regions.

The CART research team is taking the lead on this coast—with the SEAfarm facility in Kyuquot Sound as a possible platform—in a five-year national research initiative currently under review by the Natural Sciences and Engineering Research Council to explore the environmental and socio-economic issues related to integrated aquaculture (SEA-systems) on the east and west coasts of Canada. The CART team is also investigating the possibilities of energy alternatives to operate the SEAfarm and the potential for creating bioethanol from the kelp as a clean fuel for the farm.

Aquaculture is not an industry devoid of controversy. Primary concerns are issues of sea lice and interactions with wild fish, human food safety questions related to antibiotic and pesticide use, and the need to use fish meal and oil food pellets to feed the farmed fish.

“Our research doesn’t address all of these concerns,” says Cross. “Instead, we see a growing demand worldwide for seafood. This method of aquaculture can help enhance production, diversify the seafood industry and evolve best practices. It’s in all our interests to design food-production systems to be ecologically sustainable.”

the Fish Site Editor

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