A couple in California was eating at a fast-food seafood restaurant and found a worm in their fillet-O-fish combo meal. Naturally, they went ballistic and called the county health department and guess what...because the worm was dead and cooked, it didn't qualify as a health code violation. The department told the couple this was more of a customer service issue. To quote Jessie Pritchett, husband of the worm-eater, "It should be a crime for someone to sell fish with worms in it...That's ridiculous gross." Here's the full story if you want to check it out.
First of all, I make it a point not to eat at fast-food seafood establishments for the simple reason that while beef is beef and chicken is chicken (even if the quality is questionable...what part of a chicken is the McNugget?), you can batter almost any fish and pass it off as whatever you want. I guarantee restaurants like Long John Silvers are not serving up fresh Icelandic cod.
Stories like this are all the more reason to catch your own dinner, however, if you have company over and they find a worm in their fish, they can't sue you if it's dead and thoroughly cooked through. This, I think, is useful information.