Come dinnertime, wild salmon is an excellent choice. Many of the Pacific fisheries are well managed, and the fish itself is healthful and delicious. The problem is that there isn’t very much of it. Worldwide, our annual wild salmon harvest comes to about 2 billion pounds, which sounds like a lot until you divide it by 7 billion earthlings and come up with one serving per person per year.

In Seattle, there is an embarrassment of salmon riches, of course, but that’s not so nationwide, where many more people are looking to dine on our favorite fish. How to meet the demand in an environmentally sound way?

Go back as little as 10 years, and the answer was definitely not farmed salmon. “It was the thing you weren’t supposed to buy,” says Jason Clay of the World Wildlife Fund (WWF), which established the Aquaculture Stewardship Council (ASC) to create sustainability standards for shellfish and fin fish aquaculture worldwide. When the industry was new, salmon farms were accused of polluting the oceans, spreading sea lice, fostering disease, allowing escapees and depleting the stocks of forage fish, up to 7 pounds of which went into each pound of farmed Atlantic salmon.

By 2004, the WWF, working with the industry, had started to develop detailed standards. “The industry had begun to make improvements,” says Clay. Nearly a decade later, in June of this year, those ASC standards — more than 100 pages of them — were released. Farms that meet the standards will receive ASC certification, and many already have begun the process.

The Monterey Bay Aquarium’s Seafood Watch program has noted industry improvements. It awarded its very first “buy” recommendation to an open-pen salmon farm in Chile named Verlasso, a joint project of salmon producer AquaChile and DuPont, the latter of which developed a genetically engineered yeast that produces a substitute for fish oil — an important part of the salmon’s diet — that’s biochemically identical to the real thing.

For now, all farmed salmon other than Verlasso’s is rated “avoid,” but Seafood Watch aquaculture research manager Peter Bridson acknowledges that salmon farming has come a long way.


Feed, feces and other byproducts of high fish concentrations have become better controlled. “There’s an intuitive sense of feedlots. The gut reaction is that they’re a horrific source of pollution, but it seems now, from longer-term data sets, that the impacts are restricted to a small area around the pens,” says Bridson. “That’s not to say that all the concerns have gone away,” he adds, but he notes that we know more about finding sites where farms work well and accurately predicting their impact.


There are a lot fewer of them, and concern about Atlantic salmon in non-native waters, particularly, has decreased. “It’s really quite clear that Atlantic salmon are bad at colonizing outside their natural range,” says Bridson.

There are still problems within their natural range. But, according to Martin Krkosek, a biologist at the University of Toronto who studies the impact of aquaculture on wild populations, “the rate of escapees has declined dramatically.” There is evidence of farmed-salmon genes in wild Atlantic salmon, and the new ASC standards acknowledge the importance of keeping farmed salmon securely penned. To earn certification, farms must limit escapees to 300 or fewer per production cycle (about three years).

Feed conversion

That industry average of as much as 7 pounds of forage fish to grow 1 pound of farmed salmon has come down to 2.5 or 3 pounds, and the best ratios approach 1:1.

One reason for the improvement is simple: Cameras detect when the feed starts falling through the pen, indicating that the salmon have finished eating, and the feed is stopped.

The content of the feed has changed as well. Forage fish provide two essential products: fish meal for protein, and fish oil for omega-3 fatty acids. Twenty-five years ago, fish meal made up 50 percent of feed. Now, it’s 15 percent or less, as other kinds of protein are being substituted. Plant sources of omega-3s are replacing some fish oil, but they don’t provide the long-chain omega-3 fats linked to health benefits. The industry is looking into alternatives such as algae to further cut reliance on forage fish.

Another concern about feed is added astaxanthin and canthaxanthin, carotenoids that give salmon its pink color. In the wild, fish get it naturally. On the farm, it has to be added to the feed (that’s what “color added” on the label means). Canthaxanthin, in large doses, can cause retinal damage in humans, and the FDA limits the allowable amount in salmon feed accordingly.


In 2004, a controversial study found higher levels of polychlorinated biphenyls (PCBs) and dioxins in farmed salmon. That scared consumers, although the methodology of the study was criticized by health authorities, who continued to recommend eating farmed salmon. More recent research weighing the contaminant risk against health benefits from omega-3s concluded that every serving of salmon, wild or farmed, is a net positive.

Parasites and disease

This is probably the most serious problem, particularly in areas where farmed salmon and wild salmon populations coexist. “Sea lice and viruses continue to be issues,” says Bridson, and the problem varies by region. “In Chile, there’s not much evidence [of impact]; there are no native populations … There are several recent studies that show that there is still impact from sea lice in the Atlantic.”

Although “it’s fair to say that there’s pretty broad agreement that fish farms can raise parasite levels in wild fish,” Krkosek says, the fish farms are getting better at combating parasites. By using parasiticides just before the wild salmon come through the area, they decrease the chance of transferring parasites to wild populations. The chemicals, though, might have other effects. In high doses, they can harm crustaceans, but long-term, low-dose exposure is less understood. A bigger problem is that the sea lice, which can be fatal to salmon, are beginning to show resistance.

The future

ASC standards cover every aspect of salmon farming: water quality, feed composition, escapees, antibiotics, biosecurity, energy consumption, greenhouse gas emissions, worker wages and
transparency. All the major producers worldwide — who, among them, produce 70 percent of the nearly 5 billion pounds of farmed salmon harvested annually — have signed on and have committed to compliance by 2020.

Salmon farms will never have zero impact on the environment, and everyone agrees there is work to be done before that goal is met. But all involved acknowledge that progress is being made.

Come dinnertime, that’s good news.