How to Tell What a Trout is Feeding on Based on Rise Forms
On countless occasions on the Lehigh and Delaware Rivers I have seen refusal after refusal while throwing dry flies at trout that appeared to be surface feeding. Sometimes the trout may appear to be surface feeding on duns or spinners but in fact they are feeding just under the surface or in the film. Sometimes greasing up a wet fly or sinking your pattern is all you need to do to get the job done. Orvis Fly Fishing does a pretty good job at breaking down how to tell what a fish is feeding on by the appearance of the rise form. Check out the following link for more details.