Recently, Manitoba banned new hog farms in a wide swathe of the province due to environmental concerns. Now, British Columbia has suspended the issuing of new licenses for salmon farms. The ecological impact of these facilities has been mentioned here before.
Generally, the idea that open-pen aquaculture makes ecological sense for carnivorous species like salmon is fallacious. All it does is displace pressure from fishing activity from wild salmon themselves to the kind of fish they eat. Inevitably, an unconstrained fishery will destroy those stocks as well. Meanwhile, the salmon farms leach lice, excrement, and antibiotics into the waters around them.