Pacific lampreyto migration along the Columbia River is intended to be facilitated by a new $8 million project at the Bonneville Lock & Dam.
The upper portion of the fish ladder will be demolished and redesigned as part of the project, which is presently being built on the dam’s Washington side.
Fish can move upstream by using the ladder, which is a system of tiers of concrete walls that run down the dam’s side for roughly 800 feet. The serpentine component of the ladder is the problematic portion, at least for the lamprey. The final part of the fish’s journey around the dam involves navigating a series of steep S-turns in fast-moving water that are created by gaps in the concrete walls.
Lamprey will find it easier to swim through the new design since it will have softer edges and less sharp angles.
An illustration of the anticipated water velocities for redesigning the topmost section of Bonneville Dam’s Washington side fish ladder. The new design is below the present one, which is displayed above.Corps of Engineers, U.S. Army
According to Erin Kovalchuk, a project manager with the U.S. Army Corps of Engineers, we had years of research demonstrating that lamprey were truly having difficulty passing. When we performed computer modeling at that point, we were able to observe how high the water velocities were in this outdated S curve arrangement.
The fish ladder is used by a variety of fish, but biologists specifically monitor the migration of migratory species including lamprey, steelhead trout, salmon, and shad, who use the ladders the most.
In 2024, the U.S. Army Corps of Engineers reported that fewer than 40,000 Pacific lamprey passed through the main fish ladder windows. However, research indicates that over 50% of lamprey who attempt to enter the channel beneath the Bonneville Dam never pass via a fish ladder.
The Army Corps will monitor lamprey numbers over the course of the following two years to determine whether the new design is improving them.
Although they are fish, lampreys cannot swim as well as salmon. They don’t have paired fins, to start. They use a sort of sprint and suck style when swimming upstream. Lamprey adhere to a rock or the fish ladder’s concrete with their suction cup mouths, build strength, and then swim forward in a quick burst, repeating the process as they go.
According to Kovalchuk, the lamprey had nowhere to rest because of the tremendous velocity in this S form. Additionally, this new design will offer a bit more slack water.
On February 20, 2025, a Native American tribe in the Pacific Northwest caught a Pacific lamprey at the Oregon Zoo in Portland.Graves, Mark/The Oregonian
To help lamprey pass the dam and enable the Columbia River Inter-Tribal Fish Commission to collect them for a trap and haul program that aims to restore lamprey populations in Columbia River Basin tributaries upriver, the U.S. Army Corps of Engineers installed a bypass lamprey flume in March 2024. The flume rises over the fish ladder and resembles a section of metal ducting. Approximately 34,600 Pacific lamprey used the flume last year.
The tube that is seen running along the fish ladder’s wall—which is currently drained for work at Bonneville Lock & Dam—is the lamprey flume.Graves, Mark/The Oregonian
According to park ranger Katie Payne, the flume was designed to give the lamprey a more direct up-and-over shot, allowing them to skip the ladder’s flow control and serpentine parts. This pipeline is just carrying a little amount of the natural river water. They sort of suck and slither their way up and over after the lamprey gets inside.
The new fish ladder’s construction began on December 9 and is anticipated to be finished by the first week of March, in time for the salmon run to begin.
In June, Pacific lamprey begin their slightly later migration.
Although both salmon and lamprey are anadromous—that is, they live in freshwater rivers for a portion of their existence and in the ocean’s saltwater for another—they are two rather distinct animals. The 400 million-year-old Pacific lamprey is a primitive fish species without scales.
According to park ranger Tyler Ardent, people either love them or detest them; there is no middle ground. Nevertheless, they are utterly fascinating animals.
On February 20, 2025, a Native American tribe in the Pacific Northwest caught a Pacific lamprey at the Oregon Zoo in Portland.Graves, Mark/The Oregonian
Lampreys are fish parasites. They have a mouth full of teeth that they use to adhere to other fish and then bleed them; they don’t have jaws. In order to consume the blood of their host, they generate an anticoagulant in their saliva. Unlike thesea lamprey, an invasive species found in the Great Lakes, Pacific lamprey typically do not kill the animal they are feeding on.
They are indeed strange. “Yeah, they’re weird,” Ardent claimed, “but you get to be a little weird and freaky if you’ve been around for 400 million years.”
Throughout the summer, especially in July, visitors to the Bonneville Dam visitors center can witness the Pacific lamprey suctioned to the fish viewing glass.
The windows of the Washington side visitors center will reopen after the fish ladder construction is finished, however they are now boarded up.
Here is Oregon and The Oregonian/OregonLive are covered by Samantha Swindler. You may reach her at oregonian.com/sswindler.
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