Wild vs. Farmed Salmon

The controversy about eating wild vs. farmed salmon is complex, and reports available in the media, on-line, 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 and other heavy metals.  Also, wild salmon is not being over-fished – especially salmon from Alaska.  

The Washington State Department of Health’s goal is not to solve the controversy about eating farmed or wild fish but to encourage Washingtonians to eat two fish meals per week for a healthy diet. Salmon is an excellent source of omega-3 fatty acids, a type of fatty acid that our bodies cannot produce.  Omega-3 fatty acids are found in every kind of fish but are especially high in fatty fish such as salmon.  Omega-3 fatty acids found in fish promote healthy vision and brain development in infants and reduce risks of cardiovascular disease in the general population.

Environmental Concerns 

Transfer of disease
The import of Atlantic salmon eggs into the Pacific for farming purposes 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.   

Escapement
The potential escape and unintended introduction of Atlantic salmon from pens into Northwest rivers and streams is an environmental concern.  While some Atlantic salmon have escaped and reproduced, no known sustained runs have been documented despite the fact that the U.S. Bureau of Fisheries attempted to establish Atlantic salmon in the Pacific Northwest for over 50 years until the practice ceased in the 1980’s. 

An additional concern relates specifically to Pacific salmon. Loss of genetic variability could occur if farmed Pacific salmon escape from pens and breed with wild Pacific salmon populations.   

Pollution
Pollution 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 U.S. and B.C. mandate monthly monitoring of farmed salmon for sea lice and require notification of authorities and treatment if sea lice numbers exceed three lice per fish.  Some states (e.g., Alaska) have chosen to prohibit fish farms in their waters.

Other Issues
Aesthetic concerns have been raised regarding fish farms located in both pristine and developed marine areas. 

Contamination  

Most of the salmon available for human consumption today is farmed.  Several studies have found concentrations of PCBs and other contaminants at levels up to ten times higher in farmed salmon than in wild salmon.  More recent studies have found similar organic contaminant levels in farmed and wild salmon.  Farmed salmon available in U.S. markets is produced in Maine, Washington State, Canada or Chile.  Assessments of salmon from these sources showed low levels of organic contaminants in the fish.  Fish farmed in Europe were found to have higher contaminant levels. Changes in feed over the past few years have lowered contaminant levels in these fish.

Omega-3’s

Farmed fish is fattier than wild salmon – but there are qualifications regarding this:

• Because of contaminant concerns, it is often recommended that salmon be cooked in ways that reduce the fat content and that skin and fatty tissue be removed before serving.
• New feeds are being developed with less fish meal 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 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 wild fish.
• Omega-3 fatty acid levels are lower in farmed salmon, apparently because of the plant oils used in their feeds. This is part of the strategy to lower contaminant levels; plant oils have lower contaminant levels than do fish oils.  On the other hand, farmed salmon fillets contain as many grams of omega-3 fatty acids as does a wild salmon because farmed salmon are fattier than wild salmon.  Health professionals recommend that Americans increase their intake of omega-3 fatty acids, expressed as grams intake per day.

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 in omega-3 fatty acids that provide well documented benefits for the heart and brain.  While wild salmon is a great choice, farmed salmon can also be a good alternative. 

• Women of childbearing age and young children should continue to eat fish known to be low in contaminants.  List of good choices:  http://www.doh.wa.gov/ehp/oehas/fish/fishchart.htm
   
• DOH recommends that salmon and fatty fish be prepared and cooked in ways that reduce the fat content.  View demonstration:  http://www.doh.wa.gov/ehp/oehas/fish/pcbpresentation.pdf
   
• Fish Fact for Healthy Nutrition – Washington State DOH Fish Facts Web Site:
  http://www.doh.wa.gov/ehp/oehas/fish/default.htm

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. Available at URL http://fish.bc.ca/files/reports/SalmonAquaculture-MakingSenseDebate_2003_0_Complete.pdf

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 Salmon Atlantic Salmon (Salmo salar).  Monterey Bay Aquarium. http://www.mbayaq.org/cr/cr_seafoodwatch/content/media/MBA_SeafoodWatch_FarmedSalmonReport.pdf

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.