this is kinda interesting, though not terribly relevant to global fisheries, but it does have a few possibilities explaining how fish might be affected by things other than climate change... ie, dams, rainforest destruction, and pollution.
and honestly, this was rather useless but it kept appearing, and I felt bad for the site. well, it wasn't that bad, but it's not terribly specific, and really only mentions temperature and general "climate change" from conditions such as El Nino as factors that might affect fish.