I don't have as big a problem with fish as I do for land animals because of the treatment they get. In general, fish have better lives before they're killed, compared to land animals, most of which are contained and engineered from cradle to grave for purposes of consumption and profit. Fish are also simpler, less relatable organisms (especially sardines, which make up the bulk of my intake, and are more nutritious/lower mercury as well).
The increase in fish farms/GM fish is starting to cause me problems, though...