Lower Cowlitz River Tributary Resistance Board Weir Operation 2011-2015

Approximately 625,000 non-native summer steelhead smolts are released into the Cowlitz River annually. The Cowlitz River provides an extremely popular summer steelhead fishery and is considered one of the largest steelhead fisheries in the state. During 2010 through 2012, an average of 8,600 summer steelhead was harvested in the Cowlitz River. To maintain the current production levels, harvest rates should remain high and stray rates of adult fish onto spawning grounds need to be tightly controlled to keep summer steelhead from spawning with native steelhead listed under the Endangered Species Act (ESA). One method of controlling abundance of hatchery fish reaching spawning grounds is installing weirs in tributaries to capture, enumerate, and remove hatchery fish at weir sites thus minimizing interaction with wild fish. The original objective for these weirs was to exclude non-indigenous (Skamania stock) hatchery summer steelhead from straying into lower Cowlitz River tributaries and interacting (i.e., spawning and competing) with natural-origin winter steelhead. Once established, the weirs have served multiple purposes: monitoring and evaluation of fall Chinook salmon, coho salmon and steelhead, fish management (e.g., control proportion of hatchery-origin spawners), and brood stock collection (winter-run steelhead). Currently weirs are installed and operated in four major lower Cowlitz tributaries to accomplish these objectives: Olequa, Delameter, Lacamas, and Ostrander Creeks (Figure 1).