Fish Tube: How the 'Salmon Cannon' Works and Why It's Important

If you’ve been on the internet at any point in the past week, you’ve certainly come across footage of wildlife conservationists stuffing salmon into a giant plastic tube and shuttling them over obstacles. It’s so bizarre—even by the already loose standards of the web—that it briefly ignited discussions over fish welfare, its purpose, and the seeming desire of people to be similarly transported through a pneumatic tunnel into a new life.

Naturally, the “salmon cannon” has a mission beyond amusing the internet. The system was created by Whooshh Innovations, a company that essentially adopted the same kind of transportation system featuring pressurized tubing that's used in banking. Initially, the system was intended to transport fruit over long distances without bruising. At some point, engineers figured they could do the same for fish.

The fish payload is secured at the entrance of the tube—acceptable species can weigh up to 34 pounds—and moves through a smooth, soft plastic tube that conforms to their body shape. Air pressure behind them keeps them moving. The fish are jettisoned between 16 and 26 feet per second to a new location, where they emerge relatively unscathed. Because there’s no need for a water column, the tubing can cover most terrain at virtually any height.

The tubing solution is a human answer to a human problem: dams. With fish largely confined to still bodies of water thanks to dams and facing obstacles swimming upstream to migrate and spawn, fish need some kind of assistance. In the past, “fish ladders” have helped fish move upstream by providing ascending steps they can flop on, but not all fish can navigate such terrain. Another system, trapping and hauling fish like cargo, results in disoriented fish who can even forget how to swim. The Whooshh system, which has been in used in Washington state for at least five years, allows for expedient fish export with an injury rate as little as 3 percent, although study results have varied.

The video features manual insertion of the fish. In the wild, Whooshh counts on fish making semi-voluntary entries into the tubing. Once they swim into an enclosure, they’re curious enough about the tube to go inside.

If all goes well, the system could help salmon be reintroduced to the Upper Columbia River in Washington, where the population has been depleted by dams. Testing of the device there is awaiting approval from the U.S. Army Corps of Engineers.

[h/t Popular Mechanics]