While human-created dams generate useful, green energy, they disrupt a river’s natural flow, also disrupting the natural spawning runs of the indigenous salmon. Written reports of rough fishways date to 17th-century France, where bundles of branches were used to make steps in steep channels to bypass obstructions.
A pool and weir salmon ladder was built around 1830 by James Smith, a Scottish engineer on the River Teith, near Deanston, Perthshire in Scotland. In 1837, Richard McFarlan designed a fishway to bypass a dam at his water-powered lumber mill in Canada. A county in Ireland, Sligo, built the Ballisodare Fish Pass in 1852. which was used to draw salmon into a river that had not supported a fishery. As dams became more abundant and larger other methods to help the Salmon were needed.
Types
- Pool and weir
- Baffle fishway
- Fish elevator (or fish lift)
- Rock-ramp fishway
- Vertical-slot fish passage
- Fish siphon
- Fish cannon
- Borland Fish Lift
A fish cannon is a wet, flexible pneumatic tube that uses air pressure to suck in salmon one at a time and gently shoot them out into the destination water. The system was originally designed by Bellevue, Washington company Whooshh to safely move apples.
Gargantuan, ladder-less dams were entirely impassable, until the application of Whooshh’s salmon cannon. In 2014, the first salmon cannons were successfully tested at Washington’s Roza Dam.
Thanks to this invention, the Columbia river’s original salmon runs should someday be fully restored, even with the dams present. Today the fish swim into the system on their own. Inside the tubes is a kind of airlock where we make a small pressure differential to create a force so the fish moves through the tube.
And that tube is irrigated, it’s misted on the inside, so the fish is able to breathe, and it’s a frictionless environment. From the fish’s perspective, it’s a completely smooth ride and it actually feels to them like they’re in the water.
Further Reading
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