There is a long-standing debate about whether to choose seafood that is wild-caught or farmed (a product of aquaculture). Unfortunately, the answer is often not so black and white.
Wild-caught means the seafood was caught using one of several harvesting methods, some of which are not environmentally friendly. Because of many factors, including overfishing and other unsustainable practices, many species are endangered today. Wild-caught seafood may also have contaminants, depending, in part, on how polluted the waters are. Contaminants like mercury tend to accumulate most in fatty fish and large fish.
In contrast, farmed fish are raised in net-pens in the ocean or in tanks on land. According to the Food and Agriculture Organization of the United Nations, about half of all the fish consumed worldwide now come from fish farms. Atlantic salmon, trout, tilapia and catfish are the four most commonly farmed fish.
Aquaculture, which provides a steady (and relatively cheap) supply of seafood, was once thought to be the solution to dwindling fish populations. But fish farms can have a negative impact on the environment.
For example, some salmon farms, which concentrate thousands of fish in pens, may end up dumping vast quantities of waste and chemicals that pollute the water. There are also reports of farmed salmon escaping into open waters, where they can endanger wild salmon by outcompeting for their food and spreading disease. If farmed and wild salmon interbreed, this can change the genetic profile of the natural species, potentially making them unable to survive in the wild. And shrimp farms in Asia, where much of our shrimp come from, destroy mangrove forests, create pollution and deplete wild fish stocks.
Such negatives reflect an industry in need of environmental guidance and regulation, but this has been slow in coming, partly because of the international nature of aquaculture. There are fish farms working to raise fish sustainably, and these deserve consideration. Organizations promoting sustainable aquaculture and listing companies adhering to their specific guidelines include Clean Fish and the Marine Stewardship Council.
What about nutrition? According to the United States Department of Agriculture (USDA), the nutrition profile of farmed fish tends to be similar to wild. But it’s hard to know for sure because it really depends on what the fish were fed, and this varies from farm to farm. For example, some farmed salmon can be excellent sources of omega-3s, just like their wild counterparts, depending on the source and quality of the feed.
On the other hand, studies several years ago raised concern because farmed salmon from some aquaculture operations was more likely to be contaminated with harmful PCBs (polychlorinated biphenyls) and other pollutants than the wild salmon sampled. As with any product, it is important to identify the good suppliers so that you know that what you are buying is safe and healthy all around.