There is a machlokes haposkim if fish is batul beshishim or not with regards to meat, since it’s a davar sakanah. The OK labels Tropicana omega 3 OJ as OU fish. I herad besheim Rav Dovid Feinsten Shlit”a that he disagrees, and that we have no need to extend the chazal of fish and meat beyond what we have in mesorah. Being that we don’t see a sakanah today, we only have to be chosheish exactly as it’s brought down. It’s the same reason why you can buy peeled garlic cloves in most frum stores.
I was once in Target and saw Archer Farms chicken Seasoning…it was OU-D. One of the national hashgachos used to give hechsheirim to milchigs hot dog and hamburger buns. At this point, only the Triangle-K does that.