Salmon is one of the most popular fish globally, recognized for its distinctive flesh color. Consumers associate salmon with a vibrant pink or deep orange hue. This coloration is not a genetic trait, but rather a biological result of the pigments the fish absorbs from its environment. The natural color of salmon is determined entirely by the fish’s diet and its life stage.
The Source of Salmon’s Distinct Hue
The deep pink-red shade of salmon is caused by astaxanthin, a specific compound belonging to the carotenoid family of pigments. Carotenoids are responsible for the red and yellow colors found in carrots, tomatoes, and flamingos.
Astaxanthin originates primarily in microalgae and plankton, which form the base of the marine food chain. Small crustaceans, such as shrimp and krill, consume this algae and accumulate the pigment in their tissues. When wild salmon feed on these astaxanthin-rich invertebrates, they absorb the pigment and deposit it in their muscle tissue, giving the flesh its signature color.
Astaxanthin serves a biological function beyond providing color, acting as a powerful antioxidant that protects the fish’s cells and tissues from damage. This protection is important for the high-endurance swimming salmon undertake during their upstream spawning migrations. The flesh color is a direct indicator of the fish’s natural diet and its accumulation of this protective compound.
Species and Life Cycle Color Variation
The natural color of wild salmon is highly variable and depends on both the species and the stage of its life cycle. Different species of Pacific salmon consume varying amounts of astaxanthin-rich prey, leading to distinct flesh colors. Sockeye salmon, for instance, are known for their exceptionally deep red or crimson flesh because their diet consists heavily of plankton and small crustaceans that contain high concentrations of the pigment.
Conversely, species like Chinook salmon, also known as King salmon, can range from a deep red to a much paler pink, or even white in some individuals. These “white kings” have a genetic variation that prevents them from efficiently depositing the astaxanthin pigment into their muscle tissue. The fish’s body color also changes dramatically during the spawning migration from the ocean to freshwater.
As salmon cease feeding and prepare to reproduce, their external skin color transitions from silvery-blue to shades of maroon, deep red, or olive green and brown. This shift results from hormonal changes and the mobilization of astaxanthin reserves in their muscle tissue. The pigments are repurposed and transferred to the skin and the eggs, which turn bright orange-red to protect the developing embryos.
Wild Versus Farmed Salmon Pigmentation
Pigmentation differs significantly between wild and commercially farmed salmon due to their controlled diets. If farmed salmon were fed a standard feed without supplementation, their flesh would be a pale gray or off-white color. This is because they lack access to the natural diet of krill and crustaceans that provide astaxanthin in the wild.
To achieve the color consumers expect, aquaculture farmers must add carotenoid pigments to the salmon feed. These pigments are typically synthesized versions of astaxanthin or a similar carotenoid called canthaxanthin. The inclusion of these compounds is necessary for the fish’s health, as the pigment functions as an antioxidant and is important for growth and immunity.
The farming industry uses a standardized tool called the SalmoFan to grade and control the final color of the fish flesh, ensuring consistency across shades. This color reflects a carefully calculated dietary supplement rather than the unpredictable variability of the wild ocean diet. Consequently, farmed salmon labels often include the phrase “color added,” indicating the supplement in the feed, even though the pigment itself is chemically identical or similar to the one found naturally.