Why salmon flesh can be gray
A farm-raised salmon’s flesh would naturally be pale gray to off-white without dietary pigment. The familiar pink-orange color comes from astaxanthin, a reddish-orange pigment that salmon absorb from food; they do not make it themselves.
Wild salmon get astaxanthin by eating small animals such as krill and shrimp, which contain the pigment. Farmed salmon eat prepared feed, so farmers include astaxanthin in it to produce the color consumers expect. Without that ingredient, the fish can grow normally but its flesh stays much paler.
An escape wouldn’t change its color overnight
A farmed salmon that escaped into the ocean would not turn pink as soon as it began swimming freely. Its flesh color reflects the pigments accumulated through its diet over time. If it ate pigment-containing prey, its flesh could gradually become more colored; the exact change would depend on what it ate and for how long.
So the surprising contrast is not between “farm” and “wild” as places, but between two diets: the color on a salmon fillet is, in part, a record of what the fish has eaten.
