I’ve mentioned Jason Randall in the past a few times. He has a great book out on how trout see and sense. I of course later on forgot many of his insights.

So, it was great to hear his most recent interview on this Orvis Fly-Fishing Podcast. As the intro blurb writes:

Can trout see color?  Can they see UV light?  How does a trout’s window on the outside world affect how they feed and how they notice predators like us?  How can a trout see so well at night and also in bright light when they have no eyelids, and their pupils don’t constrict?

In particular, Jason talked about four ways that a fly can attract a fish: size, profile, color, and animation. He smartly says that when you float a fly at a fish and it doesn’t react, then you have the wrong size or profile. A fish that chooses not to move is a refusal.

If the fish comes closer to eyeball the fly but then turns away, he says that the size and profile are good, but that you then need to change color and/or animation. For animation, some dries feature rubber legs, CDC, or have iridescence the simulates movement (e.g., peacock herl).

Jason also says that UV-treated materials don’t really work, as trout lose the ability to see UV light when they’re a few months old.

Buy the book or give the interview a listen. Both are well worth it!