And how to balance the experts who recommend eating eight ounces of seafood a week against those who raise health concerns about the rapidly growing number of fish raised in aquaculture farms? “It’s not something that’s been exhaustively researched, but from the few studies out there on specific fish or incidents, we can put them together and get a picture that there is a possibly a real health risk to people if they are eating a lot of [farmed seafood],” says Meredith Moore, senior research and policy analyst for the nonprofit advocacy group Food and Water Watch.
Moore cites the heavy use of chemicals — including pesticides and antibiotic and antifungal drugs — in many aquaculture operations as a major concern. “There’s a lot that gets dumped into these facilities in order to try to keep fish healthy in really crowded conditions . . . and those chemicals or residues can end up on or in the fish,” she says.
In addition to potential health problems from direct exposure to such toxins, Moore notes the documented rise of antibiotic-resistant bacteria in and around aquaculture facilities and in farmed seafood itself. “There still would have to be crossover from fish pathogens to human pathogens,” she notes. “But that’s a real risk in the future.”
Several studies have also shown that farmed seafood contains higher levels of organic pollutants than wild-caught fish. These include dioxins, PCBs and metals such as mercury and lead, which have been associated with carcinogenic, reproductive and other developmental health issues.
Researchers attribute that, at least in part, to the diets of captive fish. “A lot of formulated feeds used on farms are ground-up smaller fish [from the ocean] that are then given to these fish to raise them, and somewhere in that process, they are consolidating the amount of environmental toxins,” Moore says. For example, one study found that farm-raised salmon contained higher levels of organic arsenic than wild-caught fish, while another concluded that farm-raised blue fin tuna in Japan had higher concentrations of mercury than did wild counterparts.
We have no clear idea of how widespread such problems are, says David C. Love, science director of the Public Health and Sustainable Aquaculture Project at the Johns Hopkins Center for a Livable Future. That’s because most farmed fish sold in the United States is raised outside the country.
“Imported seafood is about 80 percent of [the seafood] that’s eaten in the U.S. It’s about 50-50 farmed versus wild-caught, but the FDA only inspects about 2 percent of what’s imported, which is almost nothing,” says Love, adding that when there is oversight, what’s documented is often worrisome.