Think of it this way: farmed salmon are the new battery raised chickens. As with all livestock, there’s a great difference between intensively and extensively reared salmon. I’m not all that familiar with salmon farming across the pond, so I’m limiting my discussion to farms that rear Atlantic Salmon over on this side of the ocean.
However, salmon farming has suffered the same problems as agriculture in Europe at large. At first, it was highly profitable as salmon was perceived as a luxury good, particularly in its smoked form. But as the number of salmon farms grew, prices fell. This has led to some very intensive salmon farming, in the same way as we have intensive raising of chickens, pigs, etc. The reared salmon are generally kept in sea cages, which are simply massive cages that float off the shore and that are jam-packed full of salmon. Now this sort of promiscuity leads to disease if left unchecked, so the fish’s feed is laced with a whole cocktail of medication, including vast amounts of antibiotics. Once again, this is no different to intensive chicken farming, and in same way, there isn’t much evidence that this is particularly harmful to humans.
But here’s where the difference lies: the sea cages are right in the middle of the wild Atlantic salmon’s migratory routes. The reared salmon carry huge amounts of parasites (particularly sea lice) but can resist them because they’re pumped up to the eyeballs with drugs. So sea cages contain a much higher concentration of the things that the open ocean, and when wild salmon pass by, they’re infested. The sea cages are also breeding grounds for disease, and once again the wild salmon are not inocculated against this sort of assault. So the presence of the salmon farms adversely affects populations of wild Atlantic salmon, and God knows the things have enough trouble as it is thanks to the combined efforts of drift-netting and cutting off routes to their spawning grounds thanks to dams and pollution in rivers.
This problem is exacerbated by the fact that there is so much farmed salmon around that it’s unprofitable unless produced in huge quantities. As for the end product, it can contain up to 70% more saturated fats than a wild salmon, as the fish are fed on high-protein pellets rather and are pretty much stationary. There isn’t all that much wrong with the taste though, and the food is indeed laced with carotene pigments to make the flesh pink, as this is what the consumer expects. If you buy wild salmon from the Baltic where there are low densities of crustaceans such as shrimp, it is almost white, and this impedes its sales.
So to conclude, there’s nothing wrong with salmon farming except when it’s done intensively, the flesh is indeed artificially coloured through adding pigments to the fish’s feed but this is harmless, and it also contains far more fat that the wild equivalent.
The solution is to farm salmon less intensively, but this would entail an increase in price, which is unacceptable to the supermarkets who wish to shift large amounts of salmon, and to large amounts of consumers who have become accustomed to plentiful cheap salmon.
I’m beginning to sound like José Bové.