Thursday August 20, 2026
The Economic Times —
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.
But moving adults past the dam solves only part of the problem. The next generation must still find its way downstream.
Merwin Dam is part of PacifiCorp’s Lewis River hydroelectric project on the North Fork of the Lewis River in southwestern Washington. Because migrating salmon cannot simply pass the dam to reach upstream spawning areas, state biologists developed a system for physically transporting them.
Adult Chinook are captured and sorted into channels before being removed from the water. They are positioned in aerated tanker trucks and driven past another reservoir connected with Swift Dam. The fish are eventually released into cold mountain tributaries upstream, where they can spawn.
The approach offers a practical solution to an otherwise impassable barrier. Without transportation around the dam, the salmon would be unable to reach the higher-elevation habitat required for spawning.