The local fisherman tell me it was slow year for the salmon off of Washington State, where the salmon is rooted in culture and a major economic market, that's never good news. Fish farming has moved in, and most people know it has it's drawbacks, but a recent paper published in PNAS adds more weight to the idea that coastal fish farms can diminish the local wild population. In the wild, adult salmon do not hang out around juveniles near rivers, but instead head out for deeper waters. Coastal salmon farming changes this by keeping adult populations close to where juveniles emerge from their fresh water habitat. Millions of years of evolution have kept these two populations apart, and the juvenile salmon aren't adapted for the swarms of sea lice that come along with the artificially large number of adult salmon nearby. The sea lice attack the juveniles in such great numbers that at times 90% of the juveniles die trying to head out to sea. The authors of the paper make a point that it is not just salmon, but many temperate fish species do not associate adults near juvenile populations. Costal fish farming will have to adapt different management strategies, or possibly push the adult fish into deeper waters.
If you want to avoid those farm raised fish look for 'wild' salmon signs at your local fish monger. Or visit Prime Select Seafoods for on-line orders of the well managed, sustainable, and delicious Alaskan fishery.