Wild salmon are pink (or pinkish-orange, depending on geography) for the same reason flamingos are pink: their diets, which are heavy in krill and shrimp. But farm-raised salmon are fed a diet that renders them gray... or it would, if they weren't carefully "pigmented" to transform into more appetizing hues.


The Atlantic reports:

While [astaxanthin, an ingredient in the pigment pellets,] provides the salmon with some of the vitamins and antioxidants they'd get in the wild, salmon health isn't the selling point. It's the "pigmenting," to use feed industry parlance, that really matters, letting salmon farmers determine how red their fillets will be. (Thanks to a 2003 lawsuit, they have to alert customers to the fact of "added" coloring.) To facilitate that selection process, pharmaceutical giant Hoffman-LaRoche developed a set of standardized color cards to measure hue — which is now known as the DSM SalmoFan. (Dutch multinational DSM acquired it in 2002).


A study by DSM showed that shoppers, particularly wealthy ones, are more attracted to darker shades of salmon, which can be priced higher simply due to its resemblance to wild salmon.

Interestingly, not dying farmed salmon would make it even more affordable, but only if people would actually purchase salmon that's not pink, which doesn't seem likely. Such a psychological leap of faith would change the industry, though:

Pigmenting supplements are the most expensive component of the farmed salmon diet, constituting up to 20 percent of feed costs. But it boosts profitability. And while creating a product that fetches prices approaching those of wild-caught salmon, farmers can still churn out fillets at an industrial clip. That often makes things harder on the Pacific Northwest fishermen whose catch they're trying to emulate. An abundance of farmed salmon forces fishermen to lower prices of their wild-caught salmon in order to compete.

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