Clearheaded:
What I meant was that if the worms are mutor, they would be mutor in any fish, no matter in what percentage they are found. If the worm is assur, some fish would still be mutor without checking, if the worms don’t frequently appear in them. So unless the frozen packaged fish is possibly infested with a different species of worm, your rov must hold the anisakis to be assur, but is not concerned with fresh fish (and m’supok about canned salmon)because only a small percentage of these fish have anisakis in them.
In other words,if your rov held the anisakis is mutor, because it’s the same as described in the Shulchon Aruch, he would not assur frozen fish.