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Irrigation Diversion Fish Screening
Helping to Save the Bull Trout,
Montana's Largest and Rarest Native Trout

A diversion structure on the North Fork of the Blackfoot River funneled bull trout during their downstream migration into an irrigation canal. Native fish evolved with secondary channels or oxbows that eventually returned to the river. Irrigation canals resemble secondary channels; however most do not return to the river, leaving the fish high and dry in the irrigated fields.

Photo showing the diversion off the North Fork of the Blackfoot River
The U.S. Fish and Wildlife Service and Montana Department of Fish, Wildlife and Parks biologists surveyed the canal for bull trout presence.  Electro-shocking turned up a large number of juvenile bull trout and adult fish as large as ten pounds in the irrigation canal.

A fish friendly irrigation structure was installed on the canal in 1995. Screened drums allow water to flow through. Drums are turned by electric motors which also operate water jets that prevent debris buildup on the screens.  Bull trout follow the canal downstream, encounter the screened drums, and continue downstream via the channel, back to the North Fork.

In 1996, electro-shocking found the screen to be 100% efficient in keeping fish out of the irrigation canal. Four similar structures have also been placed on the North Fork of the Blackfoot River.

Photo showing biologists electro-shocking the canal for bull trout
Photo showing the screened drums
U.S. Fish and Wildlife Service logo     Trout Unlimited logo      Montana Fish, Wildlife and Parks logo

This structure was made possible by the Landowner,
U.S. Fish and Wildlife Service, Montana Fish, Wildlife & Parks, and Big Blackfoot Chapter of Trout Unlimited.


Return to the North Fork of the Blackfoot River

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