Granite County Sheriff Steve Immenschuh says the accident happened just after 5 o'clock on Wednesday afternoon.
says the boat flipped over near the old Micro Burst, about 25 miles up stream from the interstate.
A 55-year-old Canadian fisherman is still missing; fellow fishers and guides who were in the boat are okay and they tried looking for the man, but couldn't find him.
says rescue crews also searched by land and by air, but couldn't find the victim.
The sheriff says the man was wearing fishing waders, but didn't have a life jacket.
The search was called off Wednesday night when it got dark, but resumed Thursday morning.
added the creek is cold, with many high rocks and downed trees along the banks.