Unsustainable by Every Measure
Many erroneously think of salmon farming as the perfect gift of sustainability, both healthy for us and guilt-free for the environment. But as illustrated above and in other pages on this site, the "healthy" moniker is not quite what we are led to believe. In this section, let's snorkel around the question of sustainability of the feed.
In Richard Flanagan's book Toxic: The Rotting Underbelly of Tasmania's Salmon Industry, he referred to salmon farming as process of "food reduction". What does this mean, you may wonder? Salmon are fed more food than they provide. All species that eat other species do this -- including humans. This is why, for example, we gain less than a half kilo of weight if we eat a half kilo steak. Our body uses food energy for digestion, breathing, brain function, etc. The food we eat powers our body to survive, and we may store unused energy (i.e., calories) in the form of our own body tissues.
Back to food reduction. In the wild, as a general rule, a kilo of fish has taken 10 kilos of feed to get there. In the salmon industry, much research has gone into this question of sustainabilty. Their answers may surprise you.
Surprise 1 -- salmon are around 15% chicken and 50% soy
Skretting is one of the major feed suppliers to Tasmania's salmon farming industry. According to Skretting's Sustainability Report 2019, their salmon feed contains 13.6% poultry meal, 1.5% poultry oil, 33.6% vegetable proteins (which are primarily soy), 17.4% vegetable oils, 10.7% wheat, 10.2% fish and crustacean meal, and 10.8% fish oil . The rest is vitamins, minerals, and pigments.
Surprise 2 -- the chicken contains heads, feet, feathers, and intestines
While some may argue that repurposing poultry viscera and carcasses is a good use for biowaste, others may feel that the diseases, antibiotics, and toxic chemicals inherent to chicken offal and trimmings should exclude them from use as food for organisms destined for human consumption. Contaminants often concentrate in these tissues.
Surprise 3 -- the soybeans are genetically modified
Skretting's Sustainability Report  isn't exactly straightforward about the genetic modification (GM) question. They say that their strategy is to procure raw materials as non-GM. However, it appears evident that a majority of their soy comes from Brazil, and according to ProTerra Foundation, 95.7% of the soy crop in Brazil is GM . It therefore seems likely that farmed salmon in Tasmania are eating genetically modified food. And if they're eating it and we're eating them, well, you know!
Surprise 4 -- farmed salmon contribute to Amazon deforestation
Farmed salmon are an enormous global enterprise, and an enormous percentage of their diet comes from soy.
Surprise 5 -- the feed production process is a process of heavy metal concentration
Farmed salmon are fed on pellets that contain the viscera and frames of harvested salmon. Therefore, any contaminants in the feedstock will be in the pellets, and therefore in the salmon that we eat. Mercury is present in low concentration in the wild fish that salmon are fed. However, by using leftover body parts after filleting into the feed, this will inevitably concentrate the heavy metals from prey to predator, as surely as if it were a natural food chain.
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