That mirrors information I have read on other sites, however, I'd caution people against a knee jerk reaction and think that any amount of fish protein is bad.
IMO, having some fish in the diet provides healthy nutrients, but just like one is advised not to eat sushi or tuna everyday, neither should it be a primary protein source of their diet. And most of the salmon you eat is also farm raised, its not just pet food. And lets not forget there are issues with pet grade chicken and beef as well, but perfection isn't necessary for a healthy animal.
We still feed fish recipes once and sometimes twice a week, and no issues. Most have either salmon or "ocean fish" listed as a primary ingredient. *knock on wood*