For the second time in as many years, the Montana Department of Fish, Wildlife and Parks is operating a fish weir on the Madison downstream of Yellowstone with cooperation from Gallatin National Forest and funding from PPL Montana.
The primary objective of the weir is to learn about the characteristics of the fall rainbow trout spawning run" says Pat Clancey from the FWP field office in Ennis. Most rainbow trout tend to spawn in the spring, but the Hebgen Lake drainage has many rainbows that spawn in the fall.
Via: West Yellowstone News LINK -
Spawning Trout Art by Shari Erickson