Salmon is keystone species for region

Besides supporting fishermen, salmon is a keystone species in Alaska and the Pacific Northwest, supporting wildlife from birds to bears and orcas.

A crash could cripple dependent creatures.

Mary Ruckelshaus, a federal biologist with the Northwest Fisheries Science Center in Seattle, has been running climate models to peer into the future for Pacific Northwest salmon. Those models predict salmon will become extinct without aggressive efforts to preserve the clear, cool streams needed for spawning, efforts such as planting trees to shade streams and curtailing the amount of water siphoned off by farmers.

"It's sort of a time bomb," Ruckelshaus said.

Her models didn't factor in the potential for emerging diseases, such as the one that Richard Kocan, a fish-disease expert at the University of Washington and her former professor, has been studying.

Kocan views Ichthyophonus, or "ich," as a classic emerging disease. In the past decade, it has shown up in salmon on the Yukon, Kuskokwim and Taku rivers in Alaska and on various rivers in Washington, British Columbia and Russia.

It also has been detected in recent years in rockfish and smaller noncommercial fish in Puget Sound and elsewhere off the coasts of Oregon and Washington, and in freshwater trout on Idaho farms.

It's the kind of redistribution of disease that can be expected with climate change, Kocan said: "Everything is getting warmer, and that's how climate change is going to redistribute all kinds of disease."