Watch the trailer and see by yourself, this is one of the reasons why I do not buy farmed salmon.
Farmed salmon is significantly higher in toxins, it may contains antibiotics and pesticides. Wild salmon is superior nutritionally, it is higher in omega -3 and better environmentally.
For me the best option is wild Alaska Salmon. They are the best, even their taste and texture are different. If you buy them frozen, buy vacuum sealed and check for the FAS ( frozen at sea). It is caught, processed and frozen while still at sea.
And please, always ask were the fish comes from?