At this point, you have a good idea of the current weather, flows and environment as well as a decent guess at the rest of the day through weather reports and cloud formations.  You also have found several bugs in the river both floating through and from digging them up with a seine or similar tool as well as found some insects on the bank if there are any (assuming spring to fall here).  Now it’s time to apply your seasonal knowledge and bug behavior to make a guess that is educated and intentional.

The best way to explain this is by using an example.  Let me set the stage with some things I found on a recent trip to a local river:

I got to the river on a warm early July afternoon.  I was already rigged from a previous river so I just walked down to the river set my rod on the stream bank and began my 5-minute relax-observation time.  The river was loud which brought my attention to the amount of water, steep gradient of stream and ample pocket water I would be targeting with little open space from the foliage to cast more than 15 ft successfully.  The river appeared to be up as I could see foliage that was green and new but buried under a few inches of water near the bank.  The water clarity was tea colored, perfect for trout habitat and for giving me confidence of what was to come.  The clouds were partly cloudy with little to no wind and it was hot, likely low 80’s which is a statement at 9500 ft in elevation.

I heard plenty of insects buzzing about and the consistent tone of hoppers and cicadas in the trees and foliage around me.  The river simply sounded alive and given it was early July, just after run off had subsided, this came as no surprise, but simply a re-assurance to the stable weather I had been experiencing all week.

Five minutes went quickly as my alarm went off and I got my net and bug seine and found a semi shallow section of the 20 ft wide river and kicked around some rocks.  I picked up several large golden stoneflies, a handful of midges and small baetis mayfly nymphs and tons of free form caddis, I mean tons of caddis.  As I sat and waited for bugs to float into my seine, I noticed caddis coming off the water on the banks in the soft water with great consistency and above the water, there were golden helicopter insects flying around looking for somewhere to land.  These were golden stones and the caddis adults had already been spotted.

Now that my seining was done, I had found a ton of caddis and seen a ton of caddis as well as a golden stone or two fluttering around.  At this point, I had a pretty good idea of what to expect for the day.

The last step was to check it against the seasonal and insect behavior and see if things made sense.  It was early July, a fine time in Colorado for golden stones to still be hatching and anytime in the summer is good for a caddis hatch.  The water was certainly good for dry flies given the water color and pocket water and my overall inclination to not throw a nymph for the day led me to a decision to throw dries.  Seeing the active behavior of these insects was strong evidence that they would be successful if presented well and the weather, being stable, gave good reason to believe this would continue.

I ended with a decision to fish a two dry fly set up with a yellow stimulator size 12 as the first fly and trail a CDC elk hair caddis as the point fly.  This would allow me to easily see the flies with the larger fly and get a good presentation and cover two insects that appeared to be good choices on the river based on what I had observed.  2 hours, and 40 fish later, I was pleased with my decision and success.  Rainbows, browns and brook trout ranging 8 – 16 inches were landed and two of the larger brook trout were kept for dinner, so I could do my part to help the rainbows and browns thrive and keep the balance alive.

Bringing it Together

We can go over my decisions and thought process in a minute, but the important thing here is to see that I applied the seasonal and behavior knowledge of insects last, like a filter to make sure things made sense.  The weather and insects you can not control, only observe.  The seasonal and insect behavior can’t be controlled either, but you can use this as a filter against what you see to narrow down the results.

I’m sure nymphs would have worked that day too, but I’m fairly certain that mayfly and midge nymphs would not have been as successful.  Remember, to master fly selection, you have to find the fly that works best for the day to the best of your ability.  It isn’t about catching one fish with a fly, it’s about finding that consistent pattern and maximizing your success.  

In this scenario it was easy to rule out scuds, sowbugs, most terrestrials (though they were an option if I was wrong the first go around), midges and mayflies, leaving me with just caddis and stoneflies.  I was then able to recognize emerging and adult insects in these categories, and chose dry flies out of personal preference though I would have switched to nymphs if dries didn’t produce and would have stuck to caddis and stonefly nymphs.  Because I know caddis and stones were hatching this time of year and the weather was cooperating, I could make this guess with greater confidence.  Finding the nymphs in the stream in such numbers helped solidify my answer as well.

Do you see how all of these come together to give you the best guesses possible and narrow down your results to the smallest few flies to find the right patterns the quickest?  That is the whole purpose of fly selection.  It took me about 8 minutes to form this guess with about 3-4 more patterns I knew I was going to try next if the first ones didn’t work.  I got lucky and guessed right on the first go, making my day ultra successful.  With practice observing, learning your insects, and using seasonal filters to solidify your answers, you can master fly selection and catch more fish.

There are no two scenarios that are the same on the river, so do yourself a favor and learn how to master fly selection so you can figure out the river every time you fish.