Most canned tuna contains soy! You would think these companies wouldn't use that since it causes problems for people with gluten sensitivities. I don't have that problem but I don't like paying for soy when I want tuna!
I am sure it is in most frozen fish too, including non-battered or flavored varieties.
No, I can't buy fresh fish in my region, and even if I could, it might have been injected or treated with something to keep it pretty and odor-free.