July 31, 2007—Even as overfishing has slashed many shark populations by as much as half, some fishers continue to hunt sharks for sport—and to catch the largest trophy.

In Maine, however, a group of conservation-minded sport fishers has turned the idea of a shark tournament upside-down. These deep-sea anglers compete to catch the fish, which they then tag and release for future research, though some of the larger catches are brought back to be studied by biologists.

Look in on one of these dangerous and controversial "catch-and-release" tournaments, as sportsmen and scientists join forces to find and study the ocean's top predators.