I know some members buy feeder fish for their ducks I never have. So can't really say hopefully this thread will stay alive long enough for someone who has to chime in.
I live right above a river and most of mine haven't had fish I could catch minnows out of the river and probably small trout but I've only done it a few times.
You could try them, be sure to wash off the extra sodium. I know they eat live fish because I have seen where folks buy feeder fish for their ducks.
the only thing you want to be careful of is making sure there isn't any mold on anything you feed to any poultry.