Fish mongers have known about those things for years. If you ask nicely at the wholesaler,you get to see the huge tunnels they make in swordfish flesh. Up to about an inch across. Wont harm you if the fish is properly cooked. I would think twice about most sashimi though-Japanese chefs have higher standards than a British school leaver in a factory in Slough.
On chinese takeaway names, Eccles has a FUK YU, and Bromyard has a SHUN FAT