Sacramento River salmon at highest population level in 24 years

[Thom Little]

Wildlife managers expect more than 15,000 endangered winter-run chinook salmon to thrash their way up the Sacramento River this year, the largest number in 24 years thanks to extraordinary and expensive efforts to save the species.

But there are a couple of caution flags: An unusually high percentage of the returning fish were born in a hatchery, while an improbably low proportion of dead male fish were found by biologists counting carcasses of the salmon, which die after breeding.

An estimated 18 percent are hatchery fish this year, up from the usual 5 percent to 10 percent. Biologists limit the number of hatchery fish to avoid contaminating the wild gene pool, but an unusually large number were released three years ago as an experiment.

"It looks like the hatchery fish may have survived a lot better this year. We're not really sure why," said Alice Low, a senior fishery biologist with the state Department of Fish and Game. "It's definitely something we'll keep an eye on."


http://www.sacbee.com/state_wire/story/13884770p-14723817c.html