No proof exists that farm raised salmon is any safer than it was 10 years ago. In 2002, 700 samples of farm raised salmon showed 10 times the amount of PCBs, dioxins, pesticides, and mercury than wild salmon. What is typically called "Atlantic Salmon" is actually farmed in Chile and Canada. Farms in Scotland and Norway also show similar amounts of toxins. Farmed salmon absorb the PCBs and other industrial chemicals from the fishmeal & oils they are fed. Since the 2002 studies, no other tests have been performed. Environmental organizations oppose most salmon farming for the reason that large amounts of wild fish are used to feed the farmed fish, and that waste from the ponds pollute the oceans.
The EPA recommends that consumers eat farm raised fish no more than once a month. Use caution when purchasing frozen fish; packaging labels can be misleading. If it does not say "Wild", it probably isn't.
~ Institute for Health and the Environment, 2013