A century ago the great fishermen of New England made their living pulling thousand-pound halibut from the sea.

But in the late 1800s, the halibut all but disappeared from the Atlantic, so fishermen moved on to haddock. Then the haddock became scarce and the less-valuable cod became the fish of choice.Today, with cod fishing banned or restricted in much of New England, many fishermen are reduced to landing spiny dogfish.

The problem isn't limited to New England. According to researchers who met this week at the Woods Hole Oceanographic Institution, fisheries across the world are on the verge of collapse.

Scientists say they have the information and know-how to help preserve and restore fish populations. But they say lawmakers with the power to change the ways of the fishing industry lack the political will to take action.

Ransom S. Myers, a professor of ocean studies at Dalhousie University in Nova Scotia, has studied the populations of more than 700 species of fish worldwide. He said fish populations are becoming extinct around the world.

Myers and another fisheries scientist, Daniel Pauly of the University of British Columbia, told the symposium that regulations that limit fishing species-by-species create a domino effect where one species is devastated and fishermen move on to the next.

He said the only real way to allow the most decimated fish to recover is to create refuges in the ocean - similar to land-based wildlife refuges - where no fishing is allowed.

Scientists said because fishing is only a small fraction of the economy in the United States, management falls into the hands of the few lawmakers whose districts include fishing, and other lawmakers are usually happy to go along with their wishes.

"We really know plenty about how to manage the fisheries better," said Andy Solow, director of the marine policy center at Woods Hole. "What's missing is the political will to manage them right."