When I was in college I spent several summers on a swordfish harpoon boat fishing Georges Bank off teh east coast. Many swordfish were totally infested with worms; large (8"+) purple ones attached to the outside and often a dense population of long, white stringy ones in the meat. Even after the fish had been on ice in the hold for a week, the surface of the meat of some fish would literally crawl with severed worms when cut into steaks. I think these worms help give the swordfish the high fat content and unique texture!