Going back to the concept of “dyed” salmon, wild caught salmon naturally range in color due to the amount of astaxanthin that is present in the food they consume [1]. Astaxanthin is a pigment in the carotenoid family (where produce like pumpkins, corn, tomatoes, and carrots get their color) and salmon get this pigment in their diet by eating algae, krill, and other small crustaceans. In the wild, different species of salmon are different shades depending on how heavily they consume these organisms throughout their life; for example, Chinook salmon tend to be lighter in color because they feed more heavily on small fish which don’t produce astaxanthin, while sockeye salmon tend to be the deepest in color because they feed heavily on astaxanthin-producing zooplankton throughout their lives [2].

When it comes to farmed salmon, they receive astaxanthin through their food, which is typically a man-made pellet. These pellets contain the pigment, which can be from natural sources or made in a lab. Debate still exists over if naturally derived or lab made is better, with both types being similar in bioavailability but likely differing in the sustainability of production. In addition, wild caught and farmed salmon typically have similar levels of astaxanthin in the meat. Instead, freshness appears to be the most important factor with canned or pouch salmon having significantly less astaxanthin regardless of whether it is wild caught or farmed [3]. Currently, all farmed salmon in the US is labeled as “color added” to indicate the addition of astaxanthin to the fish food but there is no requirement to distinguish between naturally derived or synthetic pigment. The important thing to note here is that the meat of farmed salmon is not dyed after the fact and that any salmon, wild caught or farmed, would have flesh that is closer to grey or white in color if they did not eat any food that contained astaxanthin.

While both farmed and wild caught salmon are low in mercury and PCBs, farmed salmon can actually have lower levels of these contaminants [4]. In addition, both wild caught salmon and farmed salmon are similar in the amount of protein and omega-3 fatty acids [4]. In fact, some farm-raised salmon have higher levels of good omega-3s than wild-caught salmon, because of what the salmon are eating, which is something that can be manipulated in an aquaculture setup. Ultimately, there appears to be minimal differences in terms of nutrition between wild-caught and farmed salmon as well as other seafood, so it’s more important to include seafood in your diet than worry about how it is produced.

There are some reports that show farmed salmon have significantly higher levels of PCBs than wild caught salmon [6]. This is due to low levels of PCBs in the forage fish that were being used to create commercial salmon feed pellets. As salmon eat these pellets throughout their life until they are ready to be consumed, we see bioaccumulation of the contaminants in their food, which basically means the contaminants don’t pass through the salmon but rather concentrate in their tissues. However, this research is more than 20 years old and a more recent study actually found higher levels of contaminants, including PCBs, in wild fish vs. farmed fish [7]. This work found that even though the levels were higher in wild fish, all salmon had levels below the European Food Safety Authorities maximum recommended levels for weekly consumption. This shift is likely due to changes in what the farmed fish are being fed today, vs. 20 years ago.