Driftless Trout Fishing: The 90% Rules

Driftless Trout Fishing: The 90% Rules
July 1, 2026
Mike Toft, a longtime guide in the Minnesota driftless area, writes in his latest blog about the 90%/10% rule. After buying my first fly rod in 1972 and fly fishing ever since I agree with the 90/10 rule. I’ve experienced it and I’ve seen it. So, it is up to you the fly fisher if you want to make fly fishing your hobby or your sport. If your hobby then enjoy the times you go out. Relax and catch a few fish. But if you want to make it your “sport” then you will have to study, read, take trips and experience it with better fly fishers than yourself. As a sport you will have to study where the fish are and why are they there – no matter the species. This, of course, is your choice.

Here is Mike’s take on it:

Mike Toft of Whitewaterguiding.com knows from experience that 90% of the time trout are feeding sub surface

If you want to catch more and bigger trout in the driftless, it’s really helpful to govern your fishing with two “90% rules”.

Rule #1: Fisheries biologists confirm that 90% of a trout’s diet is subsurface.

The vast majority of a trout’s food—such as aquatic worms, nymphs, and crawfish—live entirely underwater. Aquatic insects spend roughly 1-2 years as underwater nymphs and only a few hours to days as flying adults So, how does this information guide your fishing strategies for catching more and bigger trout in the driftless? To begin with, perhaps you should fish with nymphs, scuds, worms and cranefly larvae most of the time.

Yes, I understand that sometimes fish size and number is not the metric of a “good day” fishing.  However, if you would like to improve your numbers, read on. I can confirm the fisheries biologist with my own sampling of trout stomach contents over the last several hundred days on the water. Yep, 10% of their content has wings (dun mayfly, caddisfly, stonefly or midge).  Most stomachs are stuffed like sausage with nymph and pupae forms or insects and even more so full of scuds and snails.  As a side note, the farming practices have also hurt our hatches tremendously thus it is even more important to learn to fish subsurface. The best way to nymph is to employ euronymphing methods.  The next best way is to use an indicator and shot.  To up your odds with an indicator, use the New Zealand wool indicators and learn to mend really well.

Rule #2: Fisheries biologists and DNR shocking crews confirm that 90% of the trout live in about 10% of the stream.

So, how will this information help you as a driftless trout angler?  Learn to identify and “read” the water. This will take time on the water.  AI, youtube shorts, Instagram Reels and Tik Toks are not the same as time on the water.   You actually have to go fishing to find out where trout hold in a particular driftless stream. Besides time on the water, you will learn more from a good book than you would from a video.  A book allows you into the mind and thought process of a good angler.  But remember, your primary goal and and way of learning should be to think, diagnose, experience, calculate and accumulate all the information you personally learn while fishing your favorite driftless stream.

In addition to a good book, try listening to a long form podcast discussing intricacies or minutia of a particular technique. Find an angler that is probably somewhere on the spectrum and really wants to share his special interest that he has fixated on with the whole world. He has gone down the rabbit hole. Listen to what he found. Let me remind you and perhaps admonish you:  The lurid glow of your iphone that is collecting your information and feeding it to an algorithm to capture even more of your attention is not a good teacher. You are choosing to intentionally make yourself dumber.  I don’t know about you, but I can’t afford to get dumber. Get smart. Go fishing.  Perhaps a bumper sticker.

If I can be a help to you, you can email me at [email protected]