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sea lice on a young salmon |
So how do fish farms try to combat sea lice? Pesticides, of course! In Canadian salmon farms, a chemical called emamectin benzoate, marketed as SLICE, is used. There is a lack of research on it, so the effects are largely unknown, but it has been shown to persist in the salmon's tissues and the environment. Usually that is not a good sign. Chemicals that persist in body tissues typically cause health problems, like DDT, polychlorinated biphenyls (PCBs), and methylmercury. Emamectin benzoate has also been shown to disrupt the growth of other crustaceans like crabs and shrimp. The label on a pesticide marketed as Proclaim, which is also emamectin benzoate, states, “This pesticide is toxic to fish, birds, mammals, and aquatic invertebrates. Do not apply directly to water, or to areas where surface water is present, or to intertidal areas below the mean high water mark. Do not contaminate water when cleaning equipment or disposing of equipment wash water.” But this is being used to treat salmon?! Although the FDA has not approved its use on fish destined for human consumption, it is not banned in other countries, and that fish is sold in the US market. So when you eat Atlantic salmon, you may be ingesting emamectin benzoate... In Canada there used to be a 68 day waiting period between the last application of the pesticide and harvest of the fish, but it was waved when the pesticide became approved for commercial use (it used to only be available for emergency use by veterinary approval). So now salmon can go to market right away with higher pesticide levels.

Pesticides aren't the only chemical added to salmon farms. The flesh of wild salmon is red-pink due to their natural diet which includes krill and shrimp (the krill and shrimp eat algae that produce red carotenoids. It's the same reason flamingos are pink!). Because farmed salmon are fed a diet lacking these things, their flesh is actually grey in color. So why does it still appear pink? They are fed an artificial dye to make them more attractive to consumers. One of these dyes has been linked to crystal formation on the human retina, although the amount you get from consuming farmed salmon is considered safe. Still weird! Farmed salmon are also given antibiotics to prevent disease. This leads to antibiotic-resistant bacteria which can harm other marine life and even humans. In a report commissioned by the World Wildlife Fund (who I do not completely trust... they apparently get a lot of funding from big oil) a group of scientists concluded that “antibiotic-resistant organisms in the marine environment will, in turn, pass their antibiotic resistance genes to other bacteria, including human and animal pathogens.” Farmed salmon also contain higher amounts of PCBs, dioxins, and other pollutants due to bioaccumulation. This means these pollutants accumulate up the food chain into the salmon. Smaller fish (like sandeels, Norwegian pout, and capelin) are ground up and incorporated into their diet, each of which contain some amount of contamination. Because the salmon are being fed these same fish over and over, the concentration of pollutants is higher than in wild salmon. Based on cancer risk from the chemicals that may be in farmed salmon, the US EPA advises that in North America, people should not consume more than one serving every two and a half months.
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a dead sea lion caught in a salmon net cage |
The salmon feed used at these farms raises more problems than just bioaccumulation. Taking these small fish from the ocean leaves less food for large wild fish and marine animals like cod, mackerel, herring, sea birds, wild salmon, and sea-trout. It takes about 3 pounds of these little fish to produce one pound of salmon, making it an unsustainable practice.Cod in particular have been hit hard because they were over-fished, and the depletion of their small prey fish added to the problem. Another environmental problem that arises from salmon farms is algal blooms. When large amounts of salmon are kept in close quarters, their waste accumulates in a confined area. This overloads the area with nutrients, which allows algae to grow out of control. As the algae is growing, it is also dying, and microorganisms feed off the dead algae. This uses up much of the oxygen in the water, which fish need to breathe. This process is called eutrophication, and it can kill the salmon and surrounding wildlife quickly. In September of 2007, Marine Harvest Canada had 227 tons of salmon die to algal blooms at a farm in British Columbia. A process that intrinsically has this much waste is not a good one! There is another really sad effect of salmon farming... marine mammal deaths. Animals like seals and dolphins are attracted to these farms. They can become entangled in the net cages and drown, or they are intentionally shot! Salmon farms can get a license to shoot them if they feel they are a threat to their salmon stock. The Canada Department of Fisheries and Oceans posted a count of mammals killed or drowned during a period of 2011. 141 California sea lions were deliberately shot, 37 harbour seals were shot or drowned, and 2 Steller sea lions were shot (which is great because they are listed as a "special concern" under Canada's federal Species at Risk Act). And keep in mind that is just a period of 2011; a matter of months. Make sure to watch the video below. It really drives home the effects of salmon farming on marine mammals. Spoiler alert/warning... it's pretty sad.
Well I think I've covered a good amount of the environmental concerns associated with salmon farming. Let's talk about why farmed salmon is a less healthy choice than wild salmon as well. I've already addressed why farmed salmon contain higher pesticide and chemical levels. But they also contain less nutrients. Their fish feed includes soy and wheat byproducts, which they can not digest as they are carnivores. This leads to a fish with less beneficial nutrients for you (See the chart below). The feed also includes feather meal; ground up feathers from poultry farms that still have blood and meat attached. I just thought that was gross. The more vegetable products in a farmed fish's diet, the less omega-3's they have. There is really no way to tell what your farmed salmon was fed when you go to the seafood market or order it at a restaurant. They also have more fat because they do not have to search for food, swim more than the length of their cage, or evade predators. This makes the meat flabby and less appetizing than wild salmon. You can tell the difference by looking at the meat. More fat means more places for chemicals to accumulate too. Persistent, organic chemicals often are "lipophilic" (fat-loving) and accumulate in the fat. If there is less fat to store the chemicals, they will be excreted from the salmon's body faster.
Salmon Nutritional Content
Wild Salmon | Farmed Salmon | |
Vitamin A | 154 I.U. | 40 I.U. |
Vitamin D | 533 I.U. | 60 I.U. |
Fat Content | 2.5% | 13% |
PCBs | 5 parts/billion | 27 parts/billion |
Sample size: 100 grams. Source: CTV British Columbia/SGS Labs
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Wild salmon, on the left, is richer in color and the white fat lines are thinner. The farmed salmon on the right has thicker fat lines and is lighter pink because its color is artificial. |
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salmon tank system |

SEAFOOD | RATING | MARKET NAMES | LOCATION | HOW CAUGHT/FARMED |
Atlantic Salmon | Farmed Salmon, Sake | Worldwide | Farmed | |
Atlantic Salmon | Verlasso (R) | Chile | Farmed | |
Coho Salmon | Sake, Silver | British Columbia | Wild-caught | |
Coho Salmon | Sake, Silver | U.S. | Farmed in Tank Systems | |
Salmon | Chinook, Coho, Chum, Keta, King, Pink, Red, Silver, Sockeye, Sake | Alaska | Drift Gillnet, Purse Seine, Troll | |
Salmon | Chinook, Coho, Chum, Keta, King, Pink, Red, Silver, Sockeye, Sake | California, Oregon, Washington | Drift Gillnet, Purse Seine, Troll | |
Salmon | Pink, Sockeye | Fraser River, Washington, | Reefnet | |
Salmon | Sockeye | Fraser River (early Summer-run), Washington | Reefnet | |
Salmon Roe | Ikura | Alaska | Drift Gillnet, Purse Seine, Troll |
And educate yourself and others! This part is really important. When consumers put pressure on an industry, it can change things. Share this article with your friends, family, and coworkers. I did days of research to make sure I got the facts straight. One website that was very helpful was that of the Coastal Alliance for Aquaculture Reform. It is a good place to get more information on the subject of salmon farming. You can even sign up to get the latest information on salmon farming. Keep yourself informed. Tell restaurants that serve net caged, farmed salmon that you would prefer if it were wild, and why. Or write them letters. If enough of their customers express this, they will make the switch. If salmon farming industries realize that people do not want salmon that causes environmental pollution, competes with native fish, causes the death of marine animals, and is full of chemicals, they will make the switch to sustainable practices like tank farming. A positive change could be coming, but it requires your support!