Farm-raised salmon are the fish equivalent of factory-farmed animals. Much like factory-farmed animals, farm-raised salmon are raised in confined quarters (essentially saltwater feedlots) that often promote ill health and have to be controlled by the widespread use of antibiotics and/or pesticides. According to the Coastal Alliance for Aquaculture Reform, farmed salmon are fed more antibiotics per pound of body weight than any livestock animal in North America.
To make matters worse, although some fisheries feed their salmon ground-up versions of the fish they might normally feed on, many farm-raised salmon are fed grains, which is not their natural diet. Because of this, farm-raised salmon have less omega-3 fats in their bodies than wild salmon.
Also, farm-raised salmon have much higher levels of cancer-causing PCBs than their wild brethren. By some reports, they also contain other highly toxic pesticides. And U.S. investigators recently found that farm-raised salmon have been eating fish meal laced with the same chemical linked to a recent pet food recall: melamine.
Even more bad news: While wild salmon get their red color from dining on krill and ingesting a natural antioxidant carotenoid called astaxanthin, farmed salmon often get their color from pigments and colorings added to their naturally gray flesh.
On the other hand, wild Alaskan salmon are among the purest of all ocean species. Residing in remote and pristine waters, they’re small fish that feed at the lower end of the food chain. And wild Alaskan salmon, including the sockeye salmon, are grown in sustainable fisheries free of antibiotics, pesticides, coloring agents, and growth hormones.
(source: The Healthiest Meals on Earth by Jonny Bowden, Ph.D., C.N.S.)