Unfortunately the salmon that are raised in farms do not swim a lot, especially through chilly seas or struggling to swim upstream. They do not swim much in their small and often crowded enclosures, they are restricted in their movements, and are fed fish food which came easily to them, and they didn't have to search or fight for it. As a result, without the right amount of exercise and food, the fat content of their body grew. Farm raised Coho salmon have been noted to have nearly triple the amount of fat of a wild salmon.
Beyond Fat and Protein Content there is the Antibiotics and Pesticide Use Issue
There are many kinds of infections and parasites such as fish lice that can affect a farmed salmon especially if it's enclosure is densely packed. To avoid this, farmed fish are vaccinated when they are small and then they are administered antibiotics and pesticides to keep them disease free.
PCB's and Mercury
A study released by the Environmental Working Group on July 30, 2003, showed that there were high levels of PCBs (chemicals that raise the chance of cancer) in farm-raised salmon in U.S. grocery stores and were much higher than those levels found in wild-caught salmon.
Additionally, some sources cite that farm-raised salmon are also contain 2 to 10 times the amount of mercury than wild-caught salmon (attributed to their feed).
The Color of Salmon
The pink color of a wild salmon is the result of them consuming pink krill. In the farms, the color is due to an artificial pigment called canthaxanthin. A fish farmer can select the exact shade of pink by the pharmaceutical company's trademarked SalmoFanTM which is very similar to selecting paint colors at the store. Without the canthaxanthin the salmon would be a shade of light grey.
Currently there is some debate over the safety of canthaxanthin which has been attributed to retinal damage when people ingest it in the form of a sunless tanning tablet - while this use has been banned in some countries such as Britain, it is still used in the U.S.
In Conclusion: Wild salmon typically have a higher nutritional value compared to farm-raised salmon and we therefore recommend Wild caught salmon whenever possible.
Federal Law requires that we warn you of the following:
1. Your individual health status and any required health care treatments can only be properly addressed by a professional healthcare provider of your choice.
2. The information in this post has not been evaluated by the FDA.