fly fishing- what flies work for yellow fish and carp in Rivers?

Answer 1

For carp in moving water, I like to match the available forage, but with impressionistic flies - not exact patterns.

For crawdads - Crazy Charlie, Wooly Bugger, Clouser Swimming nymph
For nymphs - Stoneflies, Damsels, etc (as appropriate to your local water), rubber legged hare's ear, large PT Nymphs
For minnows - Clouser Minnow, Murray's Strymph
For flies - to match your local hatch(es)

Answer 2

Crawdad patterns for sure. For carp, Let the fly sink to the bottom, then slowely strip making it pick up some silt... carp will pounce on it. Good luck!