We have fish farms here where I live in Canada and they post many problems. The use of chemicals to kill sea lice is a really frightening one for this area because it also kills lobster and that is about the only really profitable fishery left for fishermen on the east coast of Canada. Every other fishery has been practically destroyed by bad policies and over fishing. Some are starting to recover from near collapse in the 1980's but it's still uncertain if the stocks can be managed to allow them to recover.