Trying to solve the mystery of the 200,000 missing salmon

[CVX]

By Warren Cornwall
Seattle Times staff reporter

Mike Mahovlich could tell something was wrong with last year's Lake Washington sockeye-salmon run just by standing at the Ballard Locks.

Salmon carcasses floated belly-up when water rose in the Locks, which separate Lake Washington from Puget Sound. Dying salmon lay gasping on rocks along the brackish water between the Locks and the Sound.

"In my 15 years there was nothing as bad as last year, as far as just seeing dead bodies of sockeye," said Mahovlich, a fish biologist for the Muckleshoot Tribe, which helps manage the sockeye run.

But he was even more startled by the final picture that emerged late in the year: As many as 200,000 sockeye, roughly half the run, had disappeared somewhere between the Locks and their spawning grounds in streams beyond the lake.

The mystery of the missing sockeye has scientists puzzled and worried, as they try to decipher the fate of a cherished run that passes through the heart of Seattle. So far, scientists are focusing their suspicion on abnormal water temperature. And they worry that climate change could make it more than a freak occurrence.

Already there are signs that this wasn't a one-time event. In the past 34 years, three of the four years with the biggest disparity in fish numbers between the Locks and the spawning grounds have been since 2000. And recent research shows Lake Washington has warmed over the past three decades, driven in part by rising air temperatures that could be a symptom of global warming.

But for the salmon, 2004 was the worst by far. It caught the attention of researchers and convinced them that the drop wasn't just a figment of imprecise counting methods.

"I'm afraid it's not one freak year," said Eric Warner, another Muckleshoot fisheries biologist. "I think it's probably a hint of things to come."

Read more: http://seattletimes.nwsource.com/cgi...&date=20050622