Eye of the Guide


Tom Travis - March 26, 2012

Sysadmin Note
Part Two can be found here

On June 24th, 2011 we arrived on DePuy Spring Creek, the storm of the previous afternoon had passed and the day was partly cloudy and warm. The snowpack runoff had finally started and today the Yellowstone River would rise to 33,000 CFS, so the first thing that we did was to drive the creek to make sure that the river had not broken through as it had in the spring of 1996.

The river was not in the creek, however it did have an impact that most anglers were not expecting and was creating a situation of which most anglers were not aware. The height and flows of the Yellowstone River had caused the water levels in DePuy Spring Creek to rises almost eighteen inches. This was due to the river blocking the outlet at the bottom of the creek and thus the creek backed up. This really only affected the lower portion of the creek from the bridge at the house to the outlet. From the Breach Dam downstream the only effective way to fish the creek was to use a float tube, or be a least seven feet tall! The riffles above the Breached Dam and at Eva's Hut looked like glides instead of riffles, and this would cause certain problems to anglers who were not observant.

The morning was filled with nymphing action, with the trout feeding on midge worms and pupa early on and as the morning progressed there was no indication of hatch. We decided to have an early lunch, which proved a good choice. When we returned to the water we only had a few minutes to watch before the trout began to nymph right along the bottom, and using my long handled insect net I quickly discovered that the PMD Nymphs, Baetis Nymphs and a few Sulphur Nymphs were beginning to move off the bottom.

Using a double nymph rig with a PMD Nymph follow by a Baetis Nymph (separated by twelve inches) we were soon into fish and the stomach samples confirmed that the trout were indeed feeding on both species of nymphs.

By 1:15 P.M. the clouds had become thicker and finally it was totally overcast, and the duns began to appear on the water. However, at this point the trout were ignoring the duns and continuing to feed on the nymphs, only now they were much higher in the water column.

One of anglers that I was working with called me down to the flat below Eva's Hut, and as I approached I could see several trout feeding very actively. However, the angler pointed out a larger brown and rainbow trout that both seem to be doing something a little different from the other trout around them.

Most of the trout were following the nymphs up in the water column and you could take trout by using a floating emerger and nymph dropped six inches behind the floating fly, and this could be clearly seen. However, the two larger trout were cruising back in forth and maintaining about twelve inches beneath the surface while most of the other trout were holding and feeding within three inches of the surface.
He continued to catch the trout feeding close to the surface while I settled down to watch the two other trout to see if I could decipher what they were feeding on.  

As I stood there watching both of these trout feed I noticed a scraggly looking dun float toward me, and then I saw another. There was no wind at this point and no one was moving around creating bow waves so why did these duns appear to be wet? I moved slowly closer to the feeding trout and suddenly I watched a dun pop to the surface and crawl out on the surface film. Now understand I didn't see the dun emerge from the nymphal shuck on the surface film. This dun popped to the surface already emerged, which means that the dun hatched beneath the surface of the water and swam to the surface.

I had my angler switch to a longer dropper of twelve inches and use a PMD Spider (Soft Hackle Type). After we figured out the proper casting angle and how far above the feeding trout to cast we were able to take the brown trout. Unfortunately the fight that ensued spooked the rainbow and we never saw him again.

Once we had landed, pumped and photographed the trout he was released, and the stomach sample showed that all of insects in the throat were adult duns, yet we had never seen the trout rise to the surface during the forty minutes that we watched the two fish feed.

A gentle rain started falling and the PMD, Baetis and some Sulphur Duns began to explode on the surface and soon the trout were heavily surface feeding on the adult duns. All you had to do was closely observe and you could tell which dun the trout were eating and react accordingly. This went on until 5:30 P.M. , and since I was working with two very good anglers this left me plenty time to observe the trout, take photographs and even to catch a couple of fish myself as my clients stopped for a bathroom or drink break. After the hatch tapered off the rain became harder and we adjourned to my home to discuss the strange situation that we had encountered earlier in the day.

From the early days of modern fly fishing we have been conditioned to accept the fact that most mayflies leave the bottom as nymphs and slowly work their way to the surface where they break through the surface film and emerge as adults on the surface of the water. However, that is just not the way things are in nature, since in the natural world things are seldom perfect and seldom is the reality of nature in tune with the written perception of man.

In fact, there is a certain percentage of emerging mayflies in most hatches that hatch beneath the surface, swim to the surface film and crawl out as fully emerged adults. They do appear to be somewhat scraggly and do require a longer drift on the surface film to dry off and fly away.

This fact is something that I recorded years ago in my fishing journal; however it has only been recently that the scientists and some of the most progressive fishing writers have begun to mention this fact. Depending on whose article you reading the numbers will vary from species to species. With Pale Morning Duns the average is 18 to 23%. [As a point of information the amount of Callibaetis that hatch beneath the water is 27 to 30%, with Baetis hatches is it 13 to 17%.]

We discussed these facts and talked about the other times that they had seen that kind of feeding behavior and how an understanding of this behavior will allow the angler to take trout that had previously frustrated them. This fact should lead to some new wet adult dun patterns and I know one guide and two anglers who are already experimenting with new patterns.

I believe that this fact is something anglers need to spend more time examining. This may explain some of the spent adult duns and still borns that we find on the surface of the water.

There will be more to discuss and learn in part four.

Sysadmin Note
Part Four can be found here


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