Bull trout will soon return to Oregon’s Clackamas River, one of their home waters from which they were completely wiped out nearly 50 years ago.
The U.S. Fish and Wildlife Service and the Oregon Department of Fish and Wildlife will reintroduce the native fish to this major tributary of the Willamette River near Portland over the next month.
Reestablishing bull trout in this area of its former range also may lead to other bull trout reintroductions in the future to reconnect isolated populations.
Formally, the project involves a federal rule-making under the Endangered Species Act published in the June 21 Federal Register, to restore a “non-essential experimental” population.
While it is illegal to deliberately “take” (kill or harm) any listed species, this special classification under the act provides a less restrictive level of protection and precludes anyone who accidentally kills or harms the listed species from being in violation of the law.
“It’s amazing to think that bull trout evolved and thrived in Northwest rivers and lakes over thousands of years, yet it took only decades of dramatic habitat changes and overfishing to put them in peril,” said Robyn Thorson, the USFWS’ Pacific Northwest regional director. “Reaching this day gives me great hope that despite the conservation challenges for this wide-ranging species, we can find ways to restore bull trout to their home waters and reconnect fragmented native fish communities.”
Starting this summer, bull trout of different life stages will be reintroduced into historic bull trout habitat in the upper Clackamas River above the confluence with the Collawash River, within the Mt. Hood National Forest. Donor stock comes from a healthy bull trout population in the Metolius River in central Oregon. The project is expected to include additional fish transfers annually for at least seven and possibly up to 15 years. The goal is to reestablish a self-sustaining population of 300-500 spawning adult bull trout within 20 years.
Prior to the bull trout’s listing under the Endangered Species Act in 1999, ODFW and the U.S. Forest Service had been considering restoring bull trout to the Clackamas for several years. The Service, ODFW, Forest Service, NOAA Fisheries, and other partners began considering the possibility in 2005.
They worked together to evaluate the biological feasibility of a reintroduction effort, assess impacts to the broader ecosystem and especially other protected species, seek public input, and develop a plan for carrying it out.
This approach involved considering the interactions between different species, including the Clackamas populations of coho salmon, spring and fall chinook salmon, and steelhead listed under the ESA.
The Service, ODFW, and other partners developed a monitoring and adaptive management program for assessing the effectiveness of reintroduction and impacts to listed salmon and steelhead. Although population level effects to salmon and steelhead are not expected to result from the bull trout reintroduction, the project will be modified, halted, or even reversed if impacts are greater than anticipated.
No otherwise lawful activities will be prohibited to protect the Clackamas River non-essential experimental population of bull trout. Oregon’s sportfishing regulations would apply just like any other area of the state; under current fishing regulations any bull trout must be immediately released unharmed. Federal projects would not be altered or stopped to protect the reintroduced population.
From a biological standpoint, the continued existence of the rangewide bull trout population is not conditioned upon a newly restored one in the Clackamas River. Restoring bull trout to areas they once ranged is an important means of recovering the species rangewide, however, and the Service expects the Clackamas River effort may serve as a model for other similar reintroductions in the future.
The area covered by the “non-essential experimental” population provisions is the entire Clackamas River, with the exception of the Oak Grove Fork above Timothy Lake Dam (which historically was not accessible by bull trout due to an impassable natural barrier). In addition, it includes the Willamette River from Willamette Falls downstream to the confluence with the Columbia River, including the Multnomah Channel, because of the very low possibility of fish migrating downriver. On the Clackamas, the size of the covered area is about 70 river miles, but the covered area also includes countless miles of its tributaries.
Others providing assistance are the Confederated Tribes of the Warm Springs Reservation, which manage, along with ODFW, bull trout in the Metolius River; Portland General Electric, which owns and operates the Clackamas River Hydroelectric Project; NOAA Fisheries, which leads conservation efforts for listed salmon and steelhead in the region; and the U.S. Geological Survey, which is providing scientific support.
Bull trout are primarily threatened by habitat degradation and fragmentation, blockage of migratory corridors from hydroelectric and diversion dams, poor water quality, the effects of climate change, and past fisheries management practices, including targeted eradication through bounty fishing and the introduction of non-native species such as brown, lake, and brook trout.
Bull trout have been extirpated from four subbasins in the Willamette River Basin, including the Clackamas River. Once widely distributed in the Clackamas River, the last known bull trout was documented there in 1963.
The species is highly unlikely to re-colonize the area naturally due to the geographic distance to existing bull trout populations.
The Clackamas River was chosen primarily because factors that caused bull trout to disappear there have been remedied. There are currently no dams that would impede bull trout migration, since those that remain now have fish passage facilities. A significant amount of spawning and rearing habitat exists in the upper Clackamas and tributaries. In addition, much of the upper Clackamas is either part of the Federal Wild and Scenic Rivers System or part of the Oregon Scenic Waterway program.
Once plentiful throughout the coldwater rivers and lakes of the Northwest, bull trout populations in the United States are now scattered and patchy in portions of Oregon, Washington, Idaho, Montana, and Nevada. They occur in the Columbia and Snake River Basins, extending east to headwater streams in Montana and Idaho and north into Canada, and south into the Klamath River Basin in south-central Oregon. Though still wide-ranging, many of the remaining populations are small and isolated from each other.
Some bull trout populations are migratory, spending portions of their life cycle in larger rivers or lakes before returning to smaller streams to spawn, while others complete their entire life cycle in the same stream.
It is not likely that the USFWS would change the “nonessential experimental” population classification in the future. If the species recovers and is removed from the endangered species list altogether, the “nonessential experimental” population classification would be eliminated as part of the delisting process.
Agencies are approaching this effort carefully since bull trout are considered “apex predators,” meaning they will eat salmon and steelhead eggs, fry, and juveniles, as do other fish in the Clackamas River. They also will eat other fish that prey upon salmon and steelhead eggs, fry, and juveniles such as sculpin, whitefish, rainbow trout, cutthroat trout, brown trout, and brook trout.
Agency officials say predator/prey dynamics are complex and it is not possible to predict with certainty the overall impact a reestablished bull trout population will have on today’s salmon and steelhead populations in the Clackamas River.
Although there is uncertainty regarding impacts, it is informative that there are hundreds of watersheds in the western United States inhabited by bull trout, salmon, and steelhead, many of which are in Oregon, including the McKenzie, Middle Fork Willamette, Hood, Deschutes, John Day, and Imnaha rivers, and the Grand Ronde and its major tributaries including the Wenaha, Lostine, and Minam rivers.
Although studies on interactions between bull trout, salmon, and steelhead are limited, there is no evidence that predation by bull trout is a limiting factor in the status of any Oregon populations of salmon and steelhead, nor has recovery planning for federally listed salmon and steelhead populations identified bull trout predation as a possible factor limiting recovery, according to the USFWS.