As Chinook salmon swam up Washington’s Yakima River in June, many of them took an unexpected route through a vacuum tube that sucked them in and spit them out 40 feet away into a tanker truck.
The surprise journey was part of a test run by Yakama Nation Fisheries to study a system that uses a tube and gentle suction to transport live salmon across dams.
Each year salmon swim hundreds of miles against upstream to return to their birthplace to spawn. They fight their way up waterfalls and risk being eaten by bears, but dams can be impossible obstacles to traverse — and they can have a negative effect on fish populations.
In the Pacific Northwest, the Columbia, Snake and Willamette river basins alone have 12 endangered or threatened species of migratory salmon, and dams have been cited as one of the major causes of the animals’ decline.
Some smaller dams feature fish ladders (pictured right), slanted, maze-like routes fish can flop their way up to cross a dam.
For larger dams, wildlife departments and public utility companies often have to help. They’ll load them onto trucks, barges or helicopters and transport them past the manmade barrier.
But transport tubes — or what’s come to be known on the Internet as “fish cannons” — could be less labor-intensive for workers and less traumatizing for fish.
Whooshh Innovations is the creatively named Washington-based company behind the salmon cannons. Originally its tubes were used to transport fruit, but when the state began debating what to do about the salmon migrations that were blocked by dams, the company saw another use for its product.
Company owners figured that if the device could shoot apples through the tubes without damaging them, maybe it could do the same with fish.
Here’s how it works: The test at the Yakima River proves that fish will voluntarily enter the tube, and as soon as they do, a gentle vacuum sucks them in. Afterward, elevated pressure keeps the fish moving 15-22 mph until they reach the end.
Mist is sprayed the entire time to keep the fish wet as they make their way through the tube.
So far the Yakima River test runs show no immediate harm to the fish, but biologists want to study the long-term effects of such a transport system so further tests are underway.
To learn more about fish cannons and see one action, watch the video below.
Related on MNN: