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Salmon Quick to Learn Trick of Adaptation

by Richard L. Hill, Oregonian staff
The Oregonian, October 22, 2000

Sockeye rapidly develop traits to survive in new environments,
but altering their habitat still may be harmful, biologists say

Salmon seem to be nature's quick-change artists when it comes to adapting to a new habitat.

A team of Northwest biologists has found in a study that a run of sockeye salmon diverged into two populations with differing physical traits in as little as 13 generations -- or 60 to 70 years. The previous fastest examples of such changes have been about 200 to 400 generations for some insects.

The findings, published Friday in the journal Science, provide potentially good news for the region's struggling salmon runs that have faced significant changes in the past century. But the scientists caution that the research doesn't mean that alterations to a salmon's environment aren't harmful.

"In some instances, it might be that the salmon can respond to a given environmental change or human influence," said Andrew P. Hendry, an evolutionary ecologist who conducted the study while a graduate student at the University of Washington. "It's just that we can't say for sure that they always will change, or how much of a change they can handle or how quickly they can respond."

Hendry, the study's lead author who is now at the University of Massachusetts at Amherst, said the study "doesn't provide license to go out and say changes are OK or that we can wipe one population out because we can recover it from another."

The research revealed how long it took a run of sockeye salmon with common ancestors to split into two populations genetically different enough that they could no longer reproduce as successfully with each other. When that occurs, biologists say the groups are becoming "reproductively isolated."

Hendry and his colleagues studied sockeye originally from Baker Lake in northwest Washington. The salmon were introduced into Lake Washington from 1937 to 1945. After the introduction, two groups became established -- one spawning in the Cedar River, which flows into the lake, and the other along Pleasure Point Beach on the lake south of Bellevue. Runs of 100,000 to 300,000 fish now spawn in the river, while a smaller group of descendants breed along the beach.

"Sockeye salmon bury their eggs and spawn in different kinds of locations and in a variety of environments, even in a small system such as this," Hendry said. "When new populations become established at different sites, you'd expect them to evolve different adaptations, and that's in fact what happened."

On average, the body of a male beach sockeye is 13 percent deeper from back to belly than its river counterpart. Hendry said that makes them more successful in mating in waters off the beach than in the river, where they would be more likely to be stranded in shallow water. Meanwhile, a female river salmon is about 6 percent longer than a female beach sockeye.

Hendry said a river female's larger size enables her to bury her eggs deeper in gravel, decreasing the chances that the eggs will be destroyed by high water flows.

A genetic analysis conducted by the UW's Marine Molecular Biotechnology Laboratory determined the substantial reproductive isolation of the two populations. It showed that fish hatched in the river but trying to spawn at the beach had little success.

Jim Lichatowich, an independent fisheries biologist not connected with the study, said the research confirms what scientists had suspected about salmon's ability to quickly adapt to change. But whether salmon can adapt to habitat alterations brought about by fast climate change or human development "is the $64,000 question," he said.

"Whether the salmon are going to have the ability to adapt depends on the magnitude of the habitat change and the frequency that we keep changing it," said Lichatowich, who serves on the Independent Multidisciplinary Science Team for the Oregon Salmon Recovery Plan. "Continue to change the habitat, and they may never have a chance to adapt."

Richard L. Hill, Oregonian staff
Salmon Quick to Learn Trick of Adaptation
The Oregonian, October 22, 2000

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