I consistently take the hatchery fish out of the system to stay clear of having them bred with indigenous fish and also thereby pass on substandard genetics. Every hatchery fish I've caught and dressed has actually not had anything in its belly. From somber inquisitiveness I inspect. I understand gross huh.
The various other preferred view on the concern is that they take based on aggression. When they see a tiny fish in their location they get agitated and they pursue it. With swing flies the fly will resemble its getting away the location due to the existence of a larger killer which's when the steelhead strikes. This is the idea behind Spey fishing.