Bringing bull trout back
Fifty years ago, a bull trout in the Clackamas River would have been a highly unusual site.
But because of an effort to reintroduce the fish that began in 2011, bull trout have a home in the river's water once again. Seven years after the reintroduction began, project leaders continue to see bull trout successfully readapt to the river and its tributaries. The project is the first of its kind in which adult bull trout, along with their juvenile counterparts, were moved from one river basin to another.
Although bull trout are native to the Clackamas River, several factors led to reduced numbers in the 1900s, and the river's last documented bull trout sighting for many years was in 1963.
In 1998, the fish was listed as threatened under the Endangered Species Act by the U.S. Fish and Wildlife Service.
Though there are several theories for the decreased numbers of bull trout in the Clackamas River, U.S. Fish and Wildlife Service biologist Chris Allen said it likely resulted from a combination of overharvesting and habitat loss.
"Bull trout have very specific habitat requirements," Allen said. "They've never existed anywhere in the same abundance as other trout."
Bull trout on the Clackamas River spawn in the headwaters. Once the fish mature, they return to the lower watershed until they spawn, at which point they return to the headwater.
"They utilize the whole watershed," Allen explained.
Prior to Portland General Electric's creation of fish ladders and surface collectors to facilitate successful passage through the river, many bull trout were obstructed by dams.
"Any bull trout moving downstream couldn't return upstream," Allen said.
In the early 2000s, the U.S. Forest Service, U.S. Fish and Wildlife Service and Oregon Department of Fish and Wildlife collaborated on a study that examined the possibility of reintroducing bull trout to the Clackamas River.
Then, beginning in 2011, bull trout were brought from the Metolius River in Central Oregon. For six years, approximately 500 bull trout of all different ages were reintroduced to the Clackamas.
"We wanted to see whether the different life stages would adopt to the Clackamas," Allen said. "The project really had an experimental component. There had been so few bull trout introductions, and mostly with juveniles."
From the beginning, project leaders have been happy with the results of their efforts.
"There was documentation of spawning bull trout the first year they were introduced," Allen said. "That was very surprising. No one had ever moved adult bull trout from one basin to another. There was the thought that they might leave and find their prior home."
Though the U.S. Fish and Wildlife Service does not have an exact percentage of fish that survived the reintroduction, Allen noted that many bull trout seem to be faring well in the Clackamas River.
Once the bull trout were reintroduced to the river, small transmitters inside their stomachs track and document their movement as they swim up and down the river. The fish are also monitored by extracting DNA samples from the river, in which DNA shed by the bull trout is filtered from the water. This process shows which locations in the river the fish are using.
"We're seeing them start to expand," Allen said. "The spawning distribution is mostly at Pinhead Creek, but we're starting to see other tributaries. The documented survival and increased number of spawning adults all point to what we would say is early success."
Seven years after the bull trout reintroduction began, Allen said there is "a lot of cautious optimism" about the project. Right now, one of the main focuses of the project is monitoring the fish.
"As long as we see positive signs, there will be a certain level of reduced monitoring," he added, noting that the outline for the project spans 20 years.
Ultimately, project goals include reestablishing 300-500 spawning adult bull trout in the river by 2030.
Allen credits the partnerships involved in the project as one reason for its success. Along with the U.S. Fish and Wildlife Service, agencies involved in the reintroduction include Portland General Electric, the U.S. Forest Service, the National Marine Fisheries Service, Confederated Tribes of the Warm Springs and Oregon Department Fish and Wildlife.
"The state and federal partnership is a huge one," Allen said. "Rarely do you have state and federal agencies working so closely together."
Allen said that projects of this sort are not a particularly common occurrence.
"There have only been a small handful of bull trout reintroductions, and this is by far the most well thought out, planned and monitored introduction," he continued. "It really is something that's been observed."