Having fished Pollock I can confirm that they are typically riddled with nematodes, not sure why, perhaps it's their diet - the article notes they are "ground fish" which might be a euphemism for bottom feeders.

Generally, I think the historical low-value of some fish is a product of fishermen being enmeshed with the markets and communities where the fish they catch is sold. We have lost that for the most part, and therefore lower quality fish becomes salable, particularly if it is heavily processed (hence the fast-food chains being the first to pick it up).

But yeah, you're eating worms buddy.