The Monterey Bay Aquarium's Seafood Watch program has upgraded its rating of British Columbia farmed Atlantic salmon from "avoid" to "good alternative," but Canadian seafood sustainability groups still say buying farmed fish is not recommended.

The improved U.S. rating comes as part of a routine review of updated scientific research on the Atlantic salmon being raised in pens in B.C. The last assessment by Seafood Watch in 2014 landed the fish in the program's lowest ranking, red, but it's now in the middle category, yellow.

"It's an important acknowledgement of the work that salmon farmers have done in B.C. to increase their environmental performance and increase transparency," said Jeremy Dunn, executive director of the B.C. Salmon Farmers Association.

"Before today, Monterey Bay Seafood Watch program was saying to avoid farm-raised salmon from British Columbia and everywhere else, save a couple farms, and today they're saying they recommend farm-raised salmon from B.C.," said Dunn.

Now, according to a Seafood Watch report, B.C. farmed Atlantic salmon scores a 4.28 out of 10 based on a wide variety of factors.

"Yellow is an important milestone but certainly not the end of the destination," said Dunn. "There's still room to improve."

Canadians told to avoid B.C. farmed salmon

While U.S. consumers will see the new yellow rating for B.C. farmed salmon, Canadians will still see the Vancouver Aquarium's Ocean Wise rating of "not recommended." This, despite the fact that Ocean Wise relies on Seafood Watch's research and reports for most of its recommendations, including B.C. farmed salmon.

The difference is that, while Seafood Watch uses a red, yellow, or green rating, Ocean Wise simply uses a "yes" or "no," and a "yes" requires a score of 5.5/10 or higher.

farmed Pacific salmon - NOT ATLANTIC

Environmentalists still worry about the risk of diseases and sea lice spreading from farmed salmon to wild stocks. (CBC)

Kelly Roebuck speaks for SeaChoice, a group that works with Ocean Wise to inform people about their seafood-buying decisions.

"Our concern is that the Monterey Bay Aquarium has taken an "innocent until proven guilty" approach, which is not a precautionary approach or what the peer reviewed science is telling us," said Roebuck of the upgraded rating.

According to Roebuck, who looks at the same scientific research that Seafood Watch relies on, there's still a concern regarding diseases and sea lice spreading from net-penned farmed salmon to wild fish.

"We've seen a number of peer-reviewed studies come out, such as on PRV (Piscine reovirus) and heart and skeletal muscle inflammation (HSMI), which actually identifies that these are key pathogens that remain significantly concerning to wild salmon," she said.

The Seafood Watch report also notes the issue, saying: "Overall, there is clearly a pathogen and parasite concern with regard to the location of salmon farms along migration routes of wild salmon."

"There is currently insufficient evidence to conclude that population-level impacts to wild salmon are occurring due to pathogen and/or parasite transfer from salmon farms," the report concluded.

Roebuck recommends that people opt for fish with a better sustainability rating than farmed Atlantic salmon, like land-based farmed Arctic char or rainbow trout.

According to Seafood Watch's report, B.C. farmers produce 76,000 tonnes of Atlantic salmon each year. 

Dunn says that most of B.C.'s farmed salmon is bound for the U.S. market.

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