Saving the sharks

The oceans are ailing. Marine biologists say there are many reasons — pollution, coastal development. But a key problem is overfishing. Among the marine species threatened by overfishing are sharks. Millions are killed each year for their fins, which are a delicacy in Asia. The World’s Julia Kumari Drapkin met two researchers trying to save sharks. She reports from the waters off Mexico’s Yucatan Peninsula.