Yeah, most fish are full of worms, (especially bottom feeders) we used to go out to sea every morning and I'd gut the fish when we were away from the shore line because they were crawling.That's a horror story hells bells is this common!!!
If they're cleaned properly then they're absolutely fine to eat. I used to soak the odd fillet in warm water and the worms would leave the flesh and swim to the surface. Sorry marshy.