I would have to say that is very definatly a native steelhead. 100% sure that it is not a cutthroat. A cut would have yellowish fins and bright orange slashes under that head. Especially a native cut. A bow has more rounded fins that this fish has. At that time of year a native bow would be very bright as they don't spawn until lator in the spring. And just the likely hood of a bow reaching that length in a river which in terms of native resident fish wouldn't have a very big food source.I caught a fish almost exactly like this a couple of years ago and it was definatly a steelhead.

Tim