Our goal isn't to resolve the controversy about eating farmed or wild fish but to encourage Washingtonians to eat two fish meals per week that are low in contaminants. Fish is an important part of a healthy diet and salmon is an excellent source of omega-3 fatty acids. Omega-3 fatty acids are found in every kind of fish but are especially high in fish such as salmon that store a lot of oils in their muscles. Omega-3 fatty acids reduce the risk of cardiovascular disease in adults and promote healthy vision and brain development in infants.
The controversy about eating farmed verses wild salmon is complex, and reports available in the media, online, and in scientific publications often seem contradictory. Issues fall into three main categories: environmental concerns, contamination, and omega-3 fatty acid levels in edible portions. The good news is both wild and farmed salmon have low levels of mercury, PCBs, and other contaminants.
Environmental Concerns
Transfer of Disease
The import of Atlantic salmon eggs into the Pacific for farming has raised concern about possible transfer of disease to wild stocks. Restrictions on egg importation, testing of broodstock fish from which eggs are taken, and disinfection are intended to minimize disease. The disease issue is also related to how the fish are raised – high stocking densities can worsen a disease outbreak, or in some cases can be a contributing factor.
Escapes
The potential escape and unintended introduction of Atlantic salmon from marine net pens into Puget Sound and Pacific Northwest rivers and streams is an environmental concern. While some juvenile Atlantic salmon have escaped, no known sustained runs have been documented, despite the fact that federal and state agencies attempted to establish Atlantic salmon in the Pacific Northwest for many years until the practice ceased in the 1980s.
Another concern is how escaped Atlantic salmon may interact with Pacific salmon. Atlantic and Pacific salmon belong to different genera and don't produce fertile offspring. If self-reproducing Atlantic salmon populations become established in Washington, they may compete with native fish. Adult and juvenile Atlantic salmon have been found in Pacific Northwest rivers and streams. However, successful reproduction has not been observed in Washington State waters. It isn't known if farm-raised Atlantic salmon compete against wild Pacific species for food or spawning sites. Studies have shown that escaped farmed salmon – in either the Pacific or Northwest Atlantic oceans – have a low survival rate in the wild because they are accustomed to being fed. Further, Atlantic salmon (farmed or wild) cannot successfully mate with wild Pacific salmon. Pacific salmon species are not reared in marine net pens in Washington.
Pollution
Pollution (fish excrement and uneaten feed) occurs regularly under net pens, especially if they are in a low current area. Most pens are located in areas where water currents are high. Pollution from salmon net pens may affect benthic habitat directly beneath pens, but the effect is temporary and benthic habitats recover during inactive periods.
Sea Lice
Sea lice from farmed fish may infect native salmon populations. The sea lice issue is complicated, but regulations in the United States and British Columbia require monthly monitoring of farmed salmon for sea lice and notification of authorities and treatment if sea lice numbers exceed three lice per fish.
Contamination
Today, most of the salmon available for us to eat is farmed. Early studies reported high levels of PCBs and other contaminants in farmed salmon – higher than in some species of wild salmon, such as pink salmon. Follow-up studies haven't confirmed this and the consensus among scientists and regulators is that farmed salmon and wild salmon are safe foods.
Farmed salmon available in Washington state markets is produced in Washington State, Canada, Maine, or Chile. Studies on salmon from these sources have shown low levels of organic contaminants in the fish. Strict rules on contaminant levels in feed ingredients are now in place. Changes in feed have lowered contaminant levels in these fish.
Omega-3 Fatty Acids
Omega-3 fatty acids in fish are derived from plants (algae, leaves, grass). In wild salmon, the amount and type of omega-3s found are based on the algae and plankton found in their diet. In farmed salmon, the omega-3 levels are dependent on what type of feed they eat, which is made from plants, grains, and fishmeal. Farmed salmon fillets contain as many grams of omega-3 fatty acids as wild salmon because farmed salmon are fattier than wild salmon.
New feeds are being developed with less fishmeal in them and more protein derived from grains and oilseeds, such as soybeans. Fish oil is also being partially replaced with plant-derived oils. In general, the more plant-based ingredients, the lower the level of long-chain omega-3 fats in the salmon. However, fish are fed feeds containing enough fish oil to maintain omega-3 fatty acid levels equivalent or higher than most wild fish.
Health professionals recommend that we increase our intake of omega-3 fatty acids. Omega-3 fatty acids are essential nutrients for nervous system, heart, and brain health. Fish, especially oily fish such as salmon, are a rich source of omega-3 fatty acids. Those of particular importance are alpha-linolenic acid, eicosapentaenoic acid, docosopentaenoic acid, and docosahexaenoic acid. Research has shown that eicosapentaenoic acid and docosahexaenoic acid in seafood provide health benefits for the developing fetus, infants, and also for adults. Learn more about the health benefits of omega-3 fatty acids.
Summary
Balancing the health benefits of farmed salmon with contaminant levels can be confusing. Here are a few points to keep in mind:
- Keep eating salmon! Salmon is high in protein and omega-3 fatty acids that provide well documented benefits for the heart and brain. Wild salmon is a great choice and farmed salmon is a good alternative.
- Women of childbearing age and young children should continue to eat fish known to be low in contaminants. See our healthy fish guide and advice for women and children.
- Prepare and cook fish in ways that reduce the fat content. See our tips for reducing exposure to chemical contaminants in fish.
References
Easton MDL, Luszniak D, and E Von der Geest, 2002. Preliminary Examination of Contaminant Loadings in Farmed Salmon, Wild Salmon and Commercial Salmon Feed. Chemosphere (46) 1053-1074.
Gardner J and DL Peterson, 2003. Making Sense of the Salmon Aquaculture Debate: Analysis of Issues Related to Netcage Salmon Faming and Wild Salmon in British Columbia. Pacific Fisheries Resource Conservation Council.
Hites RA, Foran JA, Carpenter DO, Hamilton MC, Knuth BA, and SJ Schwager, 2004. Global Assessment of Organic Contaminants in Farmed Salmon. Science (303) 226- 229.
Mazurek R and M Elliott, 2004. Seafood Watch, Seafood Report: Farmed Atlantic Salmon (PDF). Monterey Bay Aquarium.
Nash CE (editor), 2001. The net-pen salmon farming Industry in the Pacific Northwest. U.S. Department of Commerce, NOAA Technical Memorandum NFMS-NWFSC-49, 125 p.
Waknitz FW, Iwamoto RN, and MS Strom, 2003. Interactions of Atlantic salmon in the Pacific Northwest. IV. Impacts on the local Ecosystems. Fisheries Research 62 (2003) 307-328.