The Division of Wildlife Resources wants to restore the native Bonneville Cutthroat Trout to more of the Sevier River drainage.
Starting Wednesday, the DWR will treat several creeks in Iron and Garfield counties with the piscicide Rotenone.
Wildlife officials said it will kill the fish in the targeted streams so the DWR can restock them with the native Bonneville Cutthroat Trout next year.
This is impact Mammoth, Castle and Lowder creeks.
Authorities said residents should avoid the water during this treatment.