It's a matter of experience. Those who know, know. Those who have never experienced fishing wild trout waters but only hatchery supported water can only theorize at best. Where I spend most of my trout fishing I'm blessed to be able to do both. Let me add that it's amazingly strange how the fly fishing crowd gather in droves at the hatchery supported holes, very few in the wild trout waters, and why is that ...? Wild trout are much harder to catch. And it begins with the approach to the bank of the stream. You spook a wild trout and it's adios, won't see them again today for sure - spook a hatchery trout not to worry, it'll be back directly, might even bump into your waders! If hatchery trout are getting a little harder to catch it's probably because they've already been caught a couple of times.