The various other popular sight on the issue is that they take based on hostility. When they see a little fish in their area they get upset and also they go after it. With swing flies the fly will look like its running away the location due to the fact that of the existence of a bigger killer which's when the steelhead strikes. This is the idea behind Spey fishing.
I constantly take the hatchery fish out of the system to avoid having them reproduced with indigenous fish and also thus pass on substandard genes. Every hatchery fish I've captured and also dressed has not had anything in its stomach. Out of somber inquisitiveness I check. I understand gross huh.