There is a extremely small probability, but it is highly, highly unlikely. Tiger musky have been stocked in Little Payette Lake and Lake Cascade. For a tiger musky to make it to Horseshoe Bend, it would have to pass through a dam and move downstream through several class IV-V rapids. Furthermore, tiger musky are ill-equipped to live in high gradient rivers.
The Payette River in this area more likely in inhabitated by rainbow trout, whitefish, northern pikeminnow, and other native fishes.