U.S. scientists say the creation of “mobile” marine reserves reflecting the migratory nature of far-ranging species will be needed to prevent the extinction of some vulnerable species. Speaking at the annual meeting of the American Association for the Advancement of Science, Larry Crowder, director of the Center for Ocean Solutions at Stanford University, suggested that fixed ocean reserves do little to protect many endangered species — including loggerhead and leatherback turtles and sharks — that travel great distances across oceans. “We think of protected areas as places that are locked down on a map,” Crowder said. “But places in oceans are not locked down, they move.” For instance, he said, a shifting convergence zone in the north Pacific — where two giant currents collide, bringing plankton, small fish, turtles and large predators together — is located about 1,000 miles farther north during the summer than during the winter. Researchers are urging a policy under which fishing trawlers would avoid certain areas when vulnerable species are mating, spawning, or migrating.