The highs and lows of Pacific salmon.

• Author: Pohl, John

Scientists now know the ability of the North Pacific to support Pacific salmon is not constant and exhibits long-term, climate-governed fluctuations. They are also predicting lean times ahead for this coveted fish and the industry dependent on it.

At a time when the public and industry are alarmed by the poor 1997 Bristol Bay sockeye returns and Global Warming is making headlines on a regular basis, many are concerned about climactic fluctuations and the corresponding impact on fisheries.

Are changes in oceanic conditions cyclical? Or, as a result of global warming, do they herald permanent shifts in the North Pacific's fish community structure? Many scientists from four Pacific Rim countries - the United States, Japan, Canada and Russia-search for those answers.

ALASKA'S STUDIES

Within Alaska, the Ocean Carrying Capacity Program at Auke Bay and the National Marine Fisheries Service laboratory in Juneau are focused on understanding the relationships between climate, oceanographic conditions, salmon and associated marine species in the North Pacific. Originating in 1995, the project is a coordinated effort between the U.S. and other Pacific Rim countries.

Ocean Carrying Capacity scientists are putting together a vast record of North Pacific oceanic conditions, like sea temperature and salinity (the ratio of salt to water in seawater), to see how the ocean changes over time. Simultaneously, they are looking at changes in diet, growth, survival, abundance and distribution of salmon.

Ships, nets and instruments provide only part of the picture. The salmon themselves are offering important information. Dr. Jack Helle, program manager for the OCC project at Auke Bay Laboratory, has studied changes in size and maturity of chum salmon for three decades and believes the species may be a good indicator of conditions in the North Pacific.

"The years 1971 and '73 were extremely cold winters for Alaska," said Helle. "The deer population went down, the moose population went down, and the salmon populations went down. But in 1976, suddenly many conditions changed."

WARM DAYS OF 1976

A drop in barometric pressure, which shifted ocean conditions over a broad area in the Aleutians, brought about a condition dubbed tire 1976-1977 Ocean Regime Change. The lower barometric pressure led to many climactic changes in regions of the North Pacific: precipitation decreased dramatically in the Western U.S., air temperatures warmed in the Pacific Northwest, and fewer...