Some tags can be recovered -- in fact, there's a hefty reward for them. Archival tags are surgically inserted in the abdominal cavities of bluefin and yellowfin tuna. We recover them when people who catch and clean the fish find the tags and send them back to us. The tags are inert, and don't affect the safety or taste of the fish. PAT tags -- pop-up archival tags -- release from the animals after a pre-programmed time and float to the surface. If they're not recovered, they eventually sink to the bottom of the ocean. SPOT and SRDL tags are often recovered, especially from marine mammals. If tagged animals are eaten by other animals, our experience shows (i.e. white shark eating tagged salmon shark) that the tags will eventually emerge from the animal along with other waste products and sink to the bottom.