Farmed fish
The demand for seafood has grown significantly over the last several decades and half of the world's seafood is now farmed. That can be good or bad depending on the species, and how and where it's raised.
Monterey Bay Aquarium's Seafood Watch Guide (PDF) steers customers toward Pacific Northwest farm-raised shellfish such as oysters, clams and mussels raised in areas not known to be sensitive habitat for other marine life. Shellfish are filter feeders, so they eat plankton from the water and do not require wild fish for feed. These species may actually improve water quality. Farming shellfish in nets, trays, or racks suspended in the water is an ocean-friendly alternative to dredging.
“Open-ocean aquaculture” to raise fish such as salmon is another story. It is not sustainable. Open-ocean aquaculture pollutes waters with antibiotics, chemicals and waste; threatens biodiversity; and instead of protecting wild fish, actually causes a net loss in protein — since wild fish are being overfished to make feed pellets for carnivorous farmed fish such as salmon and tuna. Steroids, pesticides, chemical dips, vaccinations and added coloring also are widely used in farmed salmon. Furthermore, millions of farmed Atlantic salmon escape, threatening wild stocks.
Fish farming can pose a threat to consumer health, too — a study by the Environmental Working Group found that farmed salmon on average have 16 times as many toxic PCBs as wild salmon.
Shrimp farming is one of the most destructive forms of aquaculture. In Latin America and Southeast Asia, coastal wetlands and mangrove forests have been destroyed to make room for shrimp farms. These coastal wetlands and mangroves are a natural nursery for many varieties of marine life and provide protection from hurricanes and other natural disasters.
Some fish farms are more environmentally friendly than others. It's possible to farm fish in “closed systems” (land-based) that do not degrade the environment. The waste from closed systems is easier to process and closed systems can better control pollution and escapes.
Genetically engineered fish
More than 35 species of genetically engineered farmed fish are being developed, including salmon, halibut, trout, tilapia, Arctic char and other seafood.
The release of genetically modified fish can cause devastating environmental and human health impacts. Many studies report that the release of GM fish into the environment threatens wild and native species.
Currently there is very little regulation by the federal government, but some states have passed laws prohibiting GM fish or requiring labels. States including Washington, Oregon, California, Alaska and Michigan have passed legislation banning the release of GE fish in state waters or requiring labeling. The FDA has declared genetically engineered (GE) salmon safe for human consumption and is set to approve it for commercial production. The transgenic fish from AquaBounty Technologies supposedly grows twice as fast as natural fish. It will not be labeled as a GE product.
Learn about why GE salmon pose a threat to human health and the environment.