No one really understands why steelhead take flies. Like salmon, as soon as steelhead enter fresh water they avoid proactively feeding as well as just depend on fatty tissue storage to make it up the stream, generate, after that go back to the ocean where they will gorge themselves and also offset the lengthy quick in the fresh water. So it's type of baffling that we fish using imitations of insects and also lure fish that they do not also eat in the sea however are respected to the streams.
The various other popular view on the concern is that they take based on hostility. When they view a tiny fish in their area they get upset as well as they go after it. With swing flies the fly will appear like its taking off the location due to the presence of a larger killer which's when the steelhead strikes. This is the thought behind Spey angling.