Will Global Warming Spell the End for New England's Fishermen?

Pete Libra is frustrated. The 40-year-old cod fisherman sees lots of fish in the ocean, and he wants to catch more. Fishing authorities see fewer, and want him to catch less.

"I'm not a scientist. But I see the fish," said Libra. His is the voice of many of the fishermen in Gloucester, the heart of a once-great fishing industry that powered fledgling America and underwrote New England's economy.

Many fishermen here feel threatened by a sweeping new set of fishing limits imposed this spring by authorities trying to rebuild fish stocks they say are depleted by overfishing and facing pressures that include climate change. Federal fishing regulators have traditionally reacted to falling stocks by putting additional curbs on fishing. But that approach may not work in the face of larger environmental changes such as global warming.

The chief fishing grounds for Massachusetts watermen are Gulf of Maine and the Georges Bank, the most westward of the famous Atlantic fishing banks off the North American coast. They are among the most famous and historically productive fishing grounds in the world; their collapse in the mid-1990s was equally historic, and the debate over how to manage the depleted stocks while nursing them back to health has been hotly contested ever since.

But the arguments are changing as scientists see more evidence of the coming impact of climate change on the Atlantic fisheries. Both the Gulf of Maine and the Georges Bank sit at the southern edge of the cod's preferred range. Fishermen have adapted to stock changes over the years, but their options may be dwindling.

"The question of the influence of fishing and the influence of the environment is tangled up," said Brian Rothschild, a professor of marine science at the University of Massachusetts, Dartmouth, who has studied aquatic stocks for more than five decades.

"There is no question that as some of the environment changes occur, some of the fish stocks are going to change," he said. "We don't know enough about it to know what's going to increase and what's going to decrease."

That gives a gloomy uncertainty to the future for New England commercial fishermen. There were an estimated 2,000 working fishermen in Gloucester in the 1940s; 50 years later the number had dropped to 400, according to a 1997 study. Fishermen glumly expect their numbers to continue to shrink.

The warming waters may hasten that. A 2007 study by the National Oceanic and Atmospheric Administration looked at codfish catch records over four decades. It concluded what fishermen who know this cold-loving fish would have predicted: As the bottom water temperature increased, the probability of catching a cod decreased.

Last year, a federal effort to coordinate research, the U.S. Global Change Research Program, found ocean warming already was forcing a migration of some species.

"The northward shifts we have seen in the area are due in part to climate change. We are starting to see some of the effects of global climate change in our area," said Janet Nye, a NOAA researcher working out of Woods Hole, Mass. She studied historical fish records and found that of 36 northwest Atlantic species, almost half had moved northward in 40 years as water temperatures warmed. She predicted the traditional stocks of cold-water fish are likely to be replaced by croaker and red hake, fish normally found farther south.

Many fishermen switched to lobster as winter flounder, a cold-water fish once abundant in fishing boat holds, declined. But lobster stocks are stressed in some areas now. Biologists on a multi-state Fisheries Commission committee have found that warmer waters, disease and fishing have depleted lobster stocks, and they recently recommended a five-year ban on lobstering from Cape Cod to Virginia.