Fish weir to provide insight for future project

by Michelle Campobasso - Colville Tribal Fish and Wildlife

A temporary picket-style salmon weir has recently been constructed in the Okanogan River by Chief Joseph Hatchery (CJH) staff.

A mile below Malott Bridge (approximately 15 miles upstream from the Okanogan River/Wells Reservoir confluence) near Brewster, the temporary weir took three weeks to construct and install in the river. Now that installation is complete, CJH staff will evaluate how summer/fall Chinook salmon, sockeye salmon and steelhead will react to it. Results from the testing site will be used to design a more permanent weir in the near future.

The temporary picket-style weir, made of steel frames and PVC pipe, was installed across the channel of the Okanogan River. It allows water to flow through it but has narrow enough slots to form a swimming barrier to adult salmon, allowing them to meander down to the trap. The structure does not connect to the west bank of the river which allows small watercraft to get around the weir.

“This summer we will watch for any negative effects the structure may cause,” said Keith Wolf, lead scientist/biologist for CJH. “We will be able to count fish, and get good estimates on the salmon returning to the Okanogan River. After closely monitoring the site for the next several weeks, we will see how salmon react to the weir and we’ll make any necessary modifications we need to for the permanent structure.”

The weir project ties directly to the CJH program and allows for adult management of annual Okanogan River summer/fall Chinook spawning escapement. A major activity of adult management requires the control and removal of hatchery-origin

salmon using selective fish capture methods to achieve the goal of more natural-origin salmon spawning in the Okanogan River. “In order to address fitness risks posed to the natural population by hatchery fish, the tribe will use the weir to reduce the hatchery-origin proportion of the overall spawner population while still meeting the spawning escapement objectives when possible,” said Jerry Marco, CCT Anadromous Division program manager. “We believe that increased fitness in the natural population will lead to an increase in productivity over time.”

“This project plays an important role in adult management of summer Chinook that are destined for the spawning grounds in the Similkameen River and the U.S. portion of the Okanogan River,” said Joe Peone, Colville Confederated Tribes (CCT) Fish and Wildlife director. “It allows managers to manage natural-origin (NOR) summer Chinook to be the primary spawners (70%) and allows us to control the number of hatchery-origin spawners (HOR) about (30%) on the breading grounds. In return, the CCT will be able to harvest the HOR summer Chinook and distribute to the CCT members,” he said. “At the same time, we want to make sure our Okanogan weir does not hinder any salmon stocks from migrating up the river. This is why we are doing a two-year feasibility study to monitor adult behavior as they approach the weir.”

The Okanogan River temporary testing structure is being funded by Grant County Public Utility District and will be operating until the end of September. The CJH staff will operate the weir and communicate with resource agencies regarding the project findings.