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FY 2016 Program Highlights


Thanks to a reintroduction and monitoring effort begun five years ago, bull trout have returned to the Clackamas River Basin for the first time in nearly 50 years. Service scientists are studying their movement and spawning patterns.
Tracking Bull trout Movement in Oregon's Clackamas River Basin
By Sean Connolly, Division of Fish and Aquatic Conservation

A multi-party, collaborative project to restore bull trout in the Oregon's upper Clackamas River Basin has reached a five-year milestone.

Since 2011, the Clackamas River Bull Trout Reintroduction Project has transferred 2,382 juvenile, 370 subadult, and 83 adult-sized bull trout from the Metolius Basin to the Clackamas in an effort to restore the species to an area where it hadn't been seen for more than 50 years.

Bull trout, a Threatened species protected under the Endangered Species Act, were extirpated from the Clackamas Basin in the 1960's as a result of over-fishing, migration barriers from hydroelectric and diversion dams, and habitat degradation. A 2007 feasibility assessment determined that because these threats have been largely mitigated, the Clackamas River could once again support a reintroduced population of bull trout.

An reintroduced adult bull trout observed in the Clackamas River's North Fork River Fish Ladder. Photo Credit: PGE

Since then, the Service has worked with the State of Oregon and the U.S. Forest Service to reintroduce the fish, considered an aquatic apex predator as ferocious as an underwater grizzly bear, back into Willamette River Basin habitat it used to occupy. The Project's goal is a self-sustaining population of 300-500 spawning adult bull trout in the upper Clackamas River and its tributaries.

The Oregon Fish and Wildlife Office has led the overall reintroduction effort for the Service, while the Fish and Aquatic Conservation program has played a key role in monitoring the translocated fish and evaluating the Reintroduction Program's success so far. The monitoring effort is multi-facteted, using minnow traps, backpack electrofishing surveys, redd (i.e. fish nest ) surveys, and detection arrays to track Passive Integrated Transponders--similar to pet microchips--placed in juvenile fish to track their movement.

Although offspring from the translocated fish haven't yet been detected, scientists estimate the number of bull trout redds has increased each year. It's a projection that continued and more rigorous monitoring needs to and will verify. The Project's Metolius Basin fish translocation phase has ended for now, but with redoubled monitoring ushering in Phase II, scientists will be able to evaluate the Reintroduction Program's success thus far, and into the future.

Clackamas Complete: A Return of Bull Trout from Freshwaters Illustrated on Vimeo.


Last Updated: May 25, 2017
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