Sustainable isn't a word most people associate with salmon farming. Given the industry's widely documented problems with pollution, sea lice, disease and its threat to wild fish stocks, many environmentally conscious consumers have dropped farmed salmon from their grocery lists altogether.
A new farmed Atlantic salmon that's marketed as less polluting and more environmentally friendly is poised to change the future of aquaculture. But how sustainable is it?
Canada's largest grocery retailer, Loblaw Cos. Ltd., announced last week it will sell WiseSource salmon, supplied by New Brunswick's True North Salmon Co., which is raised using "integrated multi-trophic aquaculture," or IMTA. The environment mimics the natural ecosystem and includes other species, such as mussels and seaweed, that feed off the waste and can also be harvested and sold.
Thierry Chopin, a professor of marine biology at the University of New Brunswick who has been leading the research on IMTA, says Loblaw's decision provides commercial validation for this experimental method.
"We are always told that [as]scientists, we like to be in the ivory towers," he said. "Well, we've left the towers and we're having an impact on the evolution of aquacultural practices."
Among scientists, conservation groups and industry experts, consensus is growing that the world needs aquaculture to feed increasing demand for seafood. However, not everyone agrees on the best practices.
Jay Ritchlin, director of marine and freshwater conservation for the David Suzuki Foundation, said IMTA has major flaws.
"It's sort of the image of sustainability without the reality," he said.
While he said IMTA is not a bad idea, it addresses only a few of the major concerns about fish farming. Like other conventionally farmed salmon, the WiseSource fish are raised in open nets in the ocean that can act like Petri dishes for sea lice and disease that can be passed on to wild fish. He added that it also doesn't prevent the escape of farmed fish.
Moreover, the farming of salmon, which are carnivorous fish, still requires significant amounts of wild fish for feed, Mr. Richtlin said.
The industry has turned to grains, as well as fish and animal-processing waste, for a greater portion of the protein and fat needed. But Mr. Ritchlin said it would be better to raise such species as tilapia and carp, which require fewer inputs.
"As we figure out how to feed ourselves and the planet, aquaculture is going to be one of the things we use, certainly," he said. "But we need to use more aquaculture that's lower down on the food chain, not higher up on the food chain."
Mr. Ritchlin believes the answer lies in closed containment farms, which eliminate the risk of escape and the spread of sea lice and disease. It also captures 100 per cent of the waste, whereas it's unknown exactly how much pollution IMTA extracts.
Under the consumer SeaChoice guide, which rates the sustainability of seafood, the benefits of IMTA still aren't enough to upgrade farmed Atlantic salmon from the red "avoid" category, Mr. Ritchlin said. He said wild Pacific salmon, which is classified as yellow, of having "some concerns," is preferable to IMTA-farmed Atlantic fish.
Representatives of Loblaw and the True North Salmon Co. said they recognize IMTA isn't perfect, but it's better than any other large-scale method.
"We're not saying this is the most sustainable; we're saying this is the most sustainable seafood that we can currently sell," said Paul Uys, vice-president of sustainable seafood at Loblaw. His company's goal is to sell only sustainable seafood by the end of 2013.
True North spokeswoman Nell Halse said that closed containment fish farming hasn't yet proven commercially viable on a large scale.
Ms. Halse said switching her company's production to a land-based, closed containment system would require at least $1-billion, as well as large areas of land, a water supply and energy to operate a filtration system.
"In this day and age, when people are starting to really look at what is the sustainability of our water supply, why wouldn't we grow our fish in a natural environment, in the ocean ... where we don't have to pump water, instead of in tanks on land?" she said.
Ms. Halse said it would be unrealistic to wait for approval from environmental groups. "They're always going to say it's not good enough and you need to do more."
Dr. Chopin said his researchers are trying to determine how, and whether, IMTA can minimize the risk of sea lice and disease. Early experiments have shown mussels can destroy sea lice in their early stages, and may be able to filter off some viruses.
His team is also experimenting with adding sea cucumbers, sea urchins, bottom feeding fish and other species within IMTA systems to increase their pollution-extracting capabilities.
"There's still plenty of things to improve and research," he said, "but ... we are, I think, in the right direction."