Be careful with the canned fish, especially canned sardines, as they risk arsenic. Canned tuna and some others can risk mercury. I wouldn't eat canned fish more than once or twice a week. Always make sure to cook them well, otherwise worms are risked. The ocean is used by us as one big garbage dump.

You shouldn't need to cook canned fish, they are cooked after canning at the factory, which is why they are shelf stable for years.