Innovative Approaches to Fisheries Management:
Sea Grant-Funded Scientists Offer Fresh Perspectives to Resolving Long-Standing Environmental and Economic Concerns
In some years, the ocean seems filled with salmon. In others, the fishing is so poor that commercial harvesters lack the incentive to set their nets.
Why?
In previous decades, scientists have studied the effects of overfishing and pollution on ocean systems to explain these wildly fluctuating cycles of boom or bust.
Today, they're investigating another possibility — natural climate variability and human-induced climate change.
"It's extremely difficult to separate natural causes from the human factors behind fisheries declines," says Robert Francis, a professor with the University of Washington's School of Aquatic & Fishery Sciences. "That's because our actions can influence global weather conditions, which in turn shape such things as nutrient cycles and water currents — two of the many components of the ocean food web."
There's strong evidence that ocean conditions shifted dramatically in the mid-1970s, he explains. Sea surface temperatures off the Washington coast became warmer. The distribution and abundance of plankton on which juvenile salmon and other fish feed also changed.
Warmer water temperatures also allowed populations of ocean predators to extend their ranges farther north, putting additional pressure on young salmon stocks. As a result of these and other climate-driven phenomena, salmon production in the Northwest was unusually poor for several successive years.
Francis and staff of the National Marine Fisheries Service, U.S. Forest Service and Oregon Department of Fish and Wildlife are currently coupling GCMs with popu-lation models for coho salmon runs in coastal Oregon.
"We picked a region and a species where much was already known and where there were existing freshwater and oceanic habitat models," he explains. "The choice of coho salmon made good sense, since these fish spend equal time — about 1-1/2 years — in both environments."
The Human Influence
The multi-agency team now hopes to couple land use forecasts with climate forecasts to get some sense of how human activity and natural cycles, in particular atmospheric warming, could affect the coastal environment. Predicting the effects of climate change will be no easy feat. Rather, it will require scientists to look ahead, decades and, possibly, centuries into the future.
"If our climate forecasts prove accurate -- and it appears that they will -- we'll need to be prepared to respond to the upcoming shifts in natural resource systems," Francis says.
A classic example is water resources in the Pacific Northwest.
"If things go in the direction we think they will, and it gets warmer and drier throughout Washington, we're going to have significant water shortages," Francis notes. "We'll need to make certain policy decisions about water use, in much the same way as our fisheries managers will be forced to plan and decide."
Historically, resource decisions have been made on a year-to-year basis, according to Francis.
"Our understanding of natural cycles and human influences may force us to take a little more long-term look, to develop some meaningful scenarios of what is likely to happen to the salmon fishery and other enterprises over the next several decades to a century," he concludes. This was certainly not the first time in world history that such a shift has occurred, according to Francis. Nor is it likely that things will remain the same in the ocean or on land for long.
With Washington Sea Grant funding, Diego Holmgren, a doctoral candidate in the School of Aquatic & Fishery Sciences, and Francis studied core samples from sediments off the west coast of Vancouver Island. Hidden at various depths in these samples were deposits of fossilized fish scales. By sorting and counting the scales in these deposits, they saw recurring cycles of boom and bust for Pacific herring and sardine populations over a span of a thousand years.
Predicting Change
Similar signs of climatic upheaval can be seen in tree rings, shellfish fossils and layers of glacial ice. Having established the historic context for such phenomena, Francis and other scientists are now redirecting their research in an attempt to predict the effects of future climate change.
"We're starting with salmon populations, using complex Global Climate Models (or GCMs), coupled with salmon life history models, to develop possible scenarios about the state of this resource in the next century," Francis says.
"We've found that GCMs can give significant insights," he offers. "They afford the opportunity to think fairly systematically about what the impacts of climate change might be."
Spring 2005
Contact David G. Gordon, Science Writer for Washington Sea Grant, for further information.