The Tualatin Valley and Clackamas River chapters of Trout Unlimited will be collecting Christmas trees and recycling them into salmon habitat through their "Christmas for Coho" program.

The conservation groups have anchored around 4,000 Christmas trees in Oregon streams since 2012 to replenish the woody debris that used to be common in local waterways.

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Members of the Tualatin Valley chapter of Trout Unlimited toss used Christmas trees into a side channel of the Necanicum River on the Oregon Coast. Michael Ellis

The trees slow the river current and give young fish a place to rest and hide from predators before they resume their journey out to the ocean. The trees also improve fish habitat by introducing a new food source for microorganisms at the bottom of the food chain.

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Mike Gentry helps organize the tree collection events for the Tualatin Valley Trout Unlimited chapter. He said he’s seen young fish swim into the tree branches immediately after they’re placed in the stream.

“The fish sense even before we can get out of the water that we have created a little safe haven for them," he said. "They know.”

Gentry said the trees help make up for the way people have changed local rivers through land development and flood management.

"Years ago, we didn’t have to worry about this because nature provided its own woody debris and cover in streams," he said. "But we people have done a pretty good job of cleaning them out and taking that woody debris away.”

Gentry's group started placing trees along the Necanicum River near Oregon’s north coast. In recent years, the trees have gone into side channels of the Clackamas River.

More than a million coastal coho salmon used to return to Oregon streams every year, but they declined dramatically last century. In 1996, only about 50,000 coastal coho coho returned to spawn in Oregon. They were listed as threatened under the Endangered Species Act in 1997. Lately, their numbers have been growing with with an average return of 200,000 coho over the last five years.

The public can drop off used Christmas trees to be recycled into salmon habitat for a $10 fee. Collection dates are Jan. 4 and 11 from 9 a.m. to 4 p.m. at Northwest Fly Fishing Outfitters, 10910 NE Halsey Street, in Portland, and the Old Fire Station next to Royal Treatment Fly Fishing, 6000 Failing St., in West Linn. To protect water quality, they cannot accept trees with flocking or tinsel.