Wild salmon are often contaminated by "sea lice" when they are exposed to farmed salmon. Containment of salmon, or any type of fish, in a specific area negatively impacts the ecosystems surrounding them because of the wastes generated. Salmon that escape from the pens of a salmon farm are far more aggressive than wild salmon and can easily starve out the wild salmon by consuming all the resources. When these farms are contained by nets or cages, predators such as dolphins, seals and sea lions are attracted. This sometimes leads to destruction of these creatures by farmers attempting to protect their stock.
Salmon farming is not fresh. Did you know salmon from farmed environments are not pink. They are actually grey. It is not natural. All farming should be banned. Please don't eat farmed salmon, only stick to really expensive wild salmon. Wild salmon is almost double the price. Just make more money.
Salmon farming actually saves wild fish from being caught, so in that respect it saves the environment. More salmon in the wild helps bear populations get more food and it keeps smaller fish populations lower due to predation. Salmon farms must raise these fish using sustainable practices to avoid runoff from these farms getting into groundwater. When these salmon are overfed, the food can get into drinking water supplies.
Salmon farming does not have the same disastrous environmental side effects that other fishing methods do. It is sustainable simply for the fact that these farmed fish aren't wild caught. When fish are wild-caught, that fishing method also picks up other, more environmentally vulnerable fish. Farming eliminates that risk entirely.
Salmon farming is not really that bad for the environment. The salmon farming industry was sparked by the popularity of eating the fish. Therefore, salmon farming has led to an increase in the population of salmon. This is not bad for the environment. In fact, salmon farming might have protected the fish from becoming endangered.