Open-net pen farmed salmon is done in the same water sources that wild salmon swim through. Farmed salmon have no natural predators so viruses are more readily transmitted to their wild counterparts. For more information: http://www.salmonconfidential.ca/

See Oceanwise's salmon recommendations:

http://www.oceanwise.ca/seafood/salmon

Tuna's much harder to farm (the fry have a tendency to kill themselves in inventive ways), but they've figured it out in recent years.

yes, and they are canibals, a tuna larvae is all mouth. But either will be domesticated or extinct. I prefer the first.

Farmed salmon is much inferior to wild salmon though.

Amen. I'm originally from the west of Ireland and we used to sometimes get fresh wild salmon from a local river off a fisherman friend of the family. The taste difference was just amazing. The farmed stuff is liking eating plastic in comparison. The other thing that makes a huge difference in my experience is to have fish that's never been frozen (someone once told me the reason has to do with the crystallization process killing the taste, although I've no idea how that works).

> (someone once told me the reason has to do with the crystallization process killing the taste, although I've no idea how that works)

The crystallization process in this case means that the solid crystal formed by water freezing into ice ruptures all of the cell walls, releasing their contents. Once that happens the chemistry of the food can change drastically as enzymes and proteins that were once only active inside cells are now floating everywhere.

In the case of frozen salmon, the taste appears to come from some sort of enzymatic process involving fatty acids [1].

[1] http://pubs.acs.org/doi/abs/10.1021/jf000021c

Crystallization bursts cell membranes, causing more rapid decay from the moment it is thawed. It is that (micro-)decay that causes the change in flavor.

Depends on your tastes. The farmed stuff has a higher fat content, which tends to be more palatable in sushi.