Pacific salmon research: facing the climate challenge

Climate change in this century may raise temperatures only a couple of degrees on Canada's west coast, but that will mean more than wearing lighter clothes. British Columbia could suffer worse floods, droughts, and forest fires. And far-reaching changes in the Pacific Ocean will affect both fish and people.

The west coast's foundation fish, Pacific salmon underlay the economy, art, and culture for First Nations. They provided the resources for a great commercial industry and growing sport fishery. But they may face major disruption from climate change.

What is likely to happen, and can humans help salmon to cope? Scientists at the Pacific Biological Station (PBS) in Nanaimo, B.C. are piecing together the puzzle. But several factors cloud the picture.

A natural cycle known as the Pacific Decadal Oscillation (PDO) creates 25- or 30-year stretches of warmer and colder temperatures (a cooler phase is just starting), which can mask climate change. Periodic “regime shifts” in the ocean ecosystem, a phenomenon explored by PBS's renowned Dr. Richard Beamish, change ocean conditions to alter predator-prey relationships. Such a shift shrank salmon abundance in the 1990's. Tracking climate change is like trying to find a fundamental fingerprint below dozens of others.

But researchers are getting it done. Robin Brown, head of the Ocean Science and Productivity Division in the Pacific Region, notes that shorter El Niño events which warm the eastern Pacific give one set of clues how salmon will react to future changes. Another set comes from the Pacific Decadal Oscillation; salmon abundance rises and falls in strong correlation with the PDO and the Aleutian low-pressure index.

Today, although certainty remains elusive, unusual occurrences suggest that major change may be starting. Pacific salmon are beginning to appear in the Arctic, some even traversing the Northwest Passage to show up at Baffin Island in the eastern Arctic. Some runs of salmon in B.C.'s Fraser River have taken to returning early, throwing off the timing that's vital to their lifecycle.

Climate change will probably bring tunas and mackerel further north. Richard Beamish notes that it may also alter the northern limit for Pacific sardines, which could find their way into Hecate Strait, inside the Queen Charlotte Islands, and even into Alaskan waters. Meanwhile, Pacific hake, now British Columbia's biggest fishery by volume, will expand their distribution throughout the Canadian zone. This may help hake fishermen, but hake are major predators of juvenile fish, including herring.

Salmon too are likely to shift north. Richard Beamish suggests that global warming will intensify winds and low-pressure areas in the North Pacific, causing more ocean upwelling and thus more biological productivity. Southern salmon runs like those of the Fraser River could suffer; others could benefit.

But much remains uncertain. One study, by PBS researcher Dr. David Welch and Japan-based Drs. Y. Ishida and K. Nagasawa, even suggests that sockeye salmon could abandon their mid-ocean feeding grounds for higher latitudes in the Bering Sea by the middle of the next century. Short of that wholesale change, some scientists speculate that certain salmon runs could fall out of synch with their environment. Changes in ocean currents, winds, temperatures, and plankton productivity could put migrating fish in the wrong place at the wrong time.

Dr. Kim Hyatt, a salmon scientist at PBS, points out that if salmon runs can survive the oceanic changes, the landward links in their chain of life become all the more critical. And there, he says, humans can do more to help.

Salmon feed little as they struggle upstream; they must reach their home spawning beds before their stored energy runs out. Researchers can relate their behaviour closely to water temperatures, Dr. Hyatt notes. One data set comes from sockeye swimming upriver a thousand kilometres from the mouth of the Columbia River in Oregon to the Okanagan region in British Columbia. Salmon wait in the cooler river waters until their home streams fall below 21 degrees Celsius. In hot years, the trip upriver has taken as long as 80 days, doubling typical times and weakening the salmon's ability to survive. Such studies help forecast reactions to climate change.

Melting glaciers will first raise, then lower river levels. That alone will make the upstream trip tougher. Other hazards besides higher temperatures could include less oxygen in the water, and flood events that can damage and kill eggs in gravel nest (redd) sites. The constant pressure of urban, agricultural, forest, and industrial development compounds the problems.

But with research providing guidelines, fishery and river managers can help give salmon a better chance in freshwater, en route to their birth streams. Water storage and timely release can control flows. Water conservation can reduce human demands. Buffer zones along riverbanks can preserve trees and foliage, which moderate temperatures and water flows, and feed rivers with their nutrients.

Combatting the effects of climate change will take carefully-planned action based on research, for Pacific salmon and other species across the country. The Pacific Biological Station leads the national fisheries component of the Canadian Climate Impacts and Adaptation Research Network (C-CAIRN), with PBS's Dr. Mark Johannes serving as Fisheries Coordinator. The national network of researchers from DFO, other federal and provincial agencies, universities, and private labs, along with other concerned parties, will improve our chances to preserve biological diversity.

For further information: see DFO's www.fishclimate.ca.