Salmon is unduly one of the most nutritious foods you could eat; high in omega 3, protein, selenium, and vitamins A, D & B12. However, all of the fresh salmon we eat in Australia comes from salmon farms. You may be surprised to learn that these salmon vary greatly from their wild counterparts not only in nutritional profile but also in pollutant content and environmental impact.

Wild vs. Farmed: Pollutants

Once considered a luxury and saved for special occasions, salmon is now widely available and reasonably priced due to the worldwide growth of salmon farming over the past 30 years. (Salmon farming is the industrial production of salmon from egg to market in a net-cage, pond or contained system). Over the past decade, however, a number of studies have raised concern about the health and environmental implications of farm salmon.

In a global assessment of farmed salmon in science 2004, 13 organic pollutants were found in amounts 10 times greater than wild salmon. The chemicals included PCB's, dieldrins, toxaphenes, dioxins and chlorinated pesticides, all 'probable' or 'possible' human carcinogens.

When farm salmon from US grocery stores was tested by the Environmental Working Group, the farm salmon, which contained up to twice the fat of wild salmon, was found to contain 16 times the PCBs found in wild salmon, 4 times the levels in beef, and 3.4 times the levels found in other seafood. (Polychlorinated Biphenyls (PCBs) are persistent, cancer-causing chemicals that were widely used from the 1930s to the 1970s and are now banned in most countries.)

In the high-density conditions common to net cages exposure to disease and its spread means that antibiotic use is common practice in the salmon farming industry. Farmed salmon are treated with antibiotics through medicated baths and food. Between 2006 and 2008 almost 18 tonnes of the antibiotics oxytetracycline and tamoxicillin were fed to Tasmanian salmon.

Wild salmon get their pink to red fish naturally from the diet they consume including crustaceans such as shrimp or krill, which are high in carotenoid pigments, mostly astaxanthin. Farmed salmon, because of their diet of fish pellets, have greyish – white colored flesh and need colourants added to their feed to give them the more appealing pink flesh. Retailers in the United States are required by the Food and Drug Administration to label salmon containing colorants. There are no similar regulations in Australia.

Wild vs. Farmed: Environment

As they grow, farm salmon need increasing amounts of wild fish fish for food, such as mackerel, anchovy and sardines. 2,162,000 tonnes of fish are taken from the worlds oceans to produce 871,200 tonnes of farm salmon. On average, it takes 2.5 kg of fish to produce 1 kg of farm salmon.

Tens of thousands of farm salmon confined to net pens produce a huge amount of marine pollution due to the release of large quantities of waste, antibiotics, and other chemicals generated in salmon farming. For more than 25 years, researchers around the world have recognized the harm from salmon farm waste and its long-term impacts on water quality, fisheries resources, and sea-bed ecology. Ben Birt of the Australian Marine Conservation Society says: “farmed salmon from sea cages are best avoided if you want to make a choice that's good for the marine environment.”

Rather than helping to take pressure off wild salmon stocks, salmon farms in fact harm wild stocks by spreading diseases and parasites to native salmon and when larger farm salmon escape into the wild and out-compete wild salmon. To protect their wild stocks of salmon, and the people who earned a living off of them, Alaska banned finfish farming, including salmon, in 1990.

Retailer Target's US stores stalled selling farm salmon products from January 2010 and now stock only sustainably wild Alaskan salmon. In a statement to the media the company said the change was made “to ensure that its salmon offerings are sourced in a sustainable way that helps to preserve abundance, species health and does not harm local habitats”.

Wild vs. Farmed: Nutrition

A CTV News Investigation in Canada (2010) compared wild and net-cage farmed salmon and found that wild salmon are more nutritious than farmed with eight times more Vitamin D and three times more Vitamin A per 100 gram serving.

FDA statistics on the nutritional content (protein and fat-ratios) of farm versus wild salmon show that:

• The fat content of farm salmon is 30-35% by weight.
• Wild salmon has a 20% higher protein content and a 20% lower fat content than farm-raised salmon.
• Farm-raised fish contain much higher amounts of pro-inflammatory omega 6 fats than wild fish.
• Omega 3 to omega 6 ratios in wild salmon is 15: 1 compared to 3: 1 in farmed.

Omega 3 fatty acids have been well documented as vitally important to brain function and the prevention and treatment of cardiovascular disease among a raft of other heath conditions. Sustainable cough deep ocean wild fish are by far our best source of omega 3 and it is critical that we protect this precious resource. Unfortunately salmon farming, the way it is currently conducted, does not provide a viable alternative. Just the fact that it takes at least 2.5kg of wild fish from diminishing stocks to produce 1kg of salmon is reason enough to think about farmed salmon's environmental credentials.

What to do?

The Alaskan wild salmon industry is one of the most sustainable in the world and is certified by the Marine Stewardship Council. In Australia our access to frozen and smoked wild Alaskan salmon is limited. Most canned salmon available is wild because farm salmon does not can well; look for wild Alaskan salmon on the label.

Alternately, sustainably Australian fish with similar omega 3 levels to wild salmon include:

Blue mackerel
Australian salmon (not related to farm Atlantic salmon from Tasmania)
Australian sardine
Australian herring
Sea bullet

For me, salmon sashimi and smoked salmon will never look the same again. What about you? Does knowing how a food is produced affect your buying decisions?

Do you feel you have access to enough information to make informed choices?