There's a high level of mercury in many of ontario's fish. I'd be sure to check that guide, and err on the side of caution.
Its good (actually, great) for your wife to get some fish oil (for omega 3 DHA etc, helps build brain tissue amongst other things). My wife picked up some from the drug or health food store....be sure to get the stuff that comes from small fish (anchovies, sardines, etc) as it usually has fewer contaminants.