Named after the river, not the animal; simple, generic fish-food fly.
hook - Dai Riki 280 #12
thread - UTC 140 grey brown
tail - elk hair dark
abdomen - dubbing muskrat/olive
wing - elk hair dark
hackle - grizzly (undersize by 1)
Part 1
mash barb, start thread at 2/3 mark, wrap to bend
clean, stack, measure (shank) a clump of elk; tie in/trim butts at 2/3 mark, cover with thread
dub thread/dub tapered body
clean, stack, measure (tips to bend) a clump of elk; trim to length, tie in, cover butts with thread