Scientists last week observed bull trout spawning in the Clackamas River basin for the first time in more than 50 years.
Survey crews tracking bull trout implanted with radio transmitters witnessed the spawning event Tuesday, Oct. 4 in the cool, dark waters of Pinhead Creek, a tributary of the Clackamas River located approximately 35 miles upstream from North Fork Reservoir in the Mt. Hood National Forest.
This is the first time bull trout have been seen spawning in the basin since the population was extirpated from the Clackamas River in the early 1960s. Listed as threatened under the federal Endangered Species Act, bull trout were reintroduced into the Clackamas on June 30, 2011, in hopes of re-establishing a naturally reproducing, self-sustaining population.
“This is pretty exciting,” said Patrick Barry, ODFW fish biologist in charge of implementation of the bull trout reintroduction project. “There was a lot of uncertainty about whether these fish would be able to survive and spawn. For this to take place this soon in areas where we thought they might spawn is very encouraging.”
Bull trout were likely extirpated from the Clackamas River as a result of constructing migration barriers from hydroelectric and diversion dams, targeted eradication with bounty fisheries, and habitat and water quality degradation from forest management and agricultural activities. For example, in the ‘60s, woody debris was removed from forest streams because people thought it was an impediment to fish passage when, in fact, it kept the water cool, played a large role in the food chain, and provided habitat that fish needed to survive.
ODFW says many of the conditions that led to the demise of the bull trout “have been corrected as the result of better science, more insightful management, increased ecosystem understanding, and stronger environmental protection. Scientists believe the river has recovered to the point where it may again support a population of wild bull trout.”
“So many times you see habitat degraded beyond the point where it will support wild fish,” said Barry. “The upper Clackamas is now in great shape. This is a really happy story.”
The 24-inch female bull trout seen excavating a redd in Pinhead Creek the other day could produce from 1,000 to 2,000 eggs, according to Barry. Juveniles will likely emerge in March or April and will take 4-6 years to reach sexual maturity.
Planning for the reintroduction of bull trout in the Clackamas River began about seven years ago. Partners in the effort include ODFW, U.S. Fish and Wildlife, U.S. Forest Service, NOAA Fisheries Service, Confederated Tribes of the Warm Springs, and Portland General Electric. Since bull trout are a top of the food chain aquatic predator they are being monitored closely to ensure they do not adversely affect native steelhead and salmon. Last summer the partners released 58 wild radio-tagged adult and sub-adult bull trout into the Clackamas and 58 juveniles. All trout released were captured in the Metolius River and Lake Billy Chinook.
Additional bull trout releases are planned annually for up to seven years.