Seabed Surgery
Photograph by Brian Skerry

Aquanauts close an incision after implanting a tracking transmitter in an anesthetized Spanish hogfish. When they finish, one will stay with the fish, moving it through the water by hand to help its gills flush out the anesthetic. "I've tagged a lot of fish in a lot of different ways," says Les Kaufman of Boston University, "but I've never seen such an excellent response as when I've done it underwater in this manner." All of his two dozen subjects swam away vigorously. Signals from their transmitters showed that they mostly stayed inside their protected home waters around Aquarius.