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The Honolulu Advertiser
Posted on: Sunday, November 18, 2001

Climate could reveal secrets of fisheries

By Jan TenBruggencate
Advertiser Science Writer

Scientists are trying to determine whether they can use climate systems to learn more about fisheries.

The Pacific Climate and Fisheries Workshop, which ended yesterday and was sponsored by the International Pacific Research Center at the University of Hawai'i, gathered ecologists, climate scientists, oceanographers, social scientists and fisheries biologists.

"We're talking about climate effects on fisheries, and we're trying to generate some new ideas," said physical oceanographer Andrew Bakun, senior scientist with the International Research Institute for Climate Prediction at the Lamont Doherty Earth Observatory at Columbia University.

Fisheries scientists historically have assumed that oceanic fish stocks were fundamentally stable, with a few annual changes, and that overfishing was one of the main alterations in the systems. But in recent years they have found that widespread climate cycles have a serious impact on fish numbers.

"It's become clear in recent years that these systems are not stationary, and this has given us certain problems," Bakun said.

Jeffrey Polovina, a Honolulu biological oceanographer, has studied some of the climate changes in the Northwestern Hawaiian Islands. There, numbers of spiny lobsters dropped in the 1990s, perhaps associated with fishing, but also with climate. Polovina was among those who recognized a dramatic change in the productivity of that region in the Pacific.

Octopus numbers declined. So did the numbers of seabirds that feed on certain kinds of marine life, and Hawaiian monk seal pups.

"Now, we're trying to understand mechanisms that cause whole ecosystems to switch from one phase to another," Polovina said.

They've seen similar changes in the Eastern Pacific, where numbers of Peruvian anchovy bloom and crash with climate changes. But those fish stocks also interact with fishing pressure, and overfishing on top of a natural downward climate phase can do serious damage to future fishing opportunity, Bakun said.

"Once you fish some species to a low level, they don't come back the way they were. It's like you put them into a durable state of lower levels," he said.

One of the research opportunities, as scientists learn more about these things, is to use natural climate cycles to study the impacts of overfishing. That way, you don't have to overfish a species to study what that does to its biology. Rather, you can simply study the natural cycles. Not easy, but potentially possible, Bakun said.

"Climate variation may be used, if we're clever, to infer the actual operation of the ecosystem," he said.

The conference was held at the East-West Center's Imin Conference Center. Co-sponsors were the International Research Center for Climate Prediction, the North Pacific Marine Science Organization, the University of Miami Center for Sustainable Fisheries, agencies of the French Institut de Recherche Pour le Developpement and other supporting organizations.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808) 245-3074.