In 2012, PacifiCorp launched a trap-and-haul program to move adult salmon upstream past Merwin Dam. 14 years later, researchers found 2 stages in the system but 1 decisive bottleneck: young salmon failing to find the artificial current downstream

Salmon migration is one of nature’s most demanding journeys. Fish must navigate long stretches of river, reach suitable spawning habitat and eventually ensure that their offspring can make the return trip toward the ocean.

For Chinook salmon in Washington’s Lewis River system, however, a hydroelectric dam has made that natural cycle impossible without human assistance. There is no fish ladder at Merwin Dam, so biologists use a trap-and-haul system to transport adult salmon around the barrier and release them upstream.