Farmed salmon are covered in sea lice, which eat chunks off them. Infection rates and severity are much worse on salmon farms than in the wild, because farmed salmon generally live in dirty, crowded net pens.
When wild salmon swim past salmon farms, they get severe infestations of sea lice, which can be deadly. Kills more salmon than fishing, in fact — perhaps up to 80% of affected populations. Every salmon farm on the west coast of North America is a threat to the survival of wild salmon.
Don’t eat farmed salmon.
It’s possible that, in the future, salmon farms will have better louse control tactics and will no longer threaten the existence of wild salmon. That would be great, but it’s not true yet.
And yes, I’m avoiding something, how can you tell?