The Corps is carrying out Research, Monitoring, and Evaluation (RM&E) to assess the effects of the injunction measures on UWR Chinook salmon and UWR steelhead. RM&E results can be found here.
One of the RM&E methods being used is screw traps:
Screw traps (above) are rudimentary tools that give Corps biologists basic data about the fish and the Corps will use them for the next couple years. The data is partially influenced by other factors, including traps only spans a small portion of any water body and they are designed to primarily capture smaller fish that cannot swim out of the device. Click here to learn more.
Rotary screw traps are fish sampling devices that have a cone-shaped collector device - or 'rotary screw' - suspended between two pontoons that spins in conjunction of the river hydraulics in order to collect a portion of fish traveling downstream. These fish are captured in the rotary screw and funneled to a box at the rear of the trap where they are held until staff arrive to remove debris and count, measure, and release the collected fish.
Operation of rotary screw traps provide general information about downstream fish passage, primarily for juvenile spring Chinook and winter steelhead herein. Extended operation of rotary screw traps provide information such as species presence over time and migration or run-timing. A variety of additional sampling measures can also be performed as warranted such as fish condition assessments and marking or tagging of individual fish (e.g., through the use of PIT tags). Data collected by rotary screw traps is influenced by a variety of factors including, rotary screw traps only spans a small portion of any water body and they are designed to primarily capture smaller fish that are traveling downstream and that cannot swim out of the device.
The Corps began operating rotary screw traps at multiple sites in the Willamette River basin in 2021 in partial fulfillment of RM&E requirements associated with the interim injunction that requires the Corps to undertake specified actions to improve fish passage and monitor results at several Willamette Valley Project dams for the benefit of Upper Willamette River (UWR) spring Chinook salmon and UWR winter steelhead salmon listed under the Endangered Species Act (ESA). Operation of the rotary screw traps will continue, generally seasonally and at multiple sites, through 2024 as directed by the interim injunction and court-ordered implementation plans to the extent feasible.