If you're used to fishing small to medium-sized rivers, you probably enjoy fishing stonefly nymphs in the same size range. There are great opportunities to fish the smaller stoneflies all along the mountains of the Wasatch Front.
Rivers such as the Logan, Blacksmith, South Fork of the Ogden, East Canyon Creek and Provo all seem to have a good supply of the smaller stoneflies in the stretches that are adequate for their survival.
The stonefly that is fun to imitate and fish is the Little Brown Stonefly. It is hard to identify the actual species and genus without the help of a professional aquatic entymologist or a good self taught amateur, so most of us just have to guess that the critters are little and brown.
It is possible (if you want to go this far) to take a sample to a college or university and see if they can identify it for you. I haven't found this necessary. As long as you or a friend can tie flies, you should be able to tie up a reasonable imitation of the sample bug.
According to some of the books and articles I have read, I believe that a lot of the smaller brown stoneflies I have collected are of the Nemour genus, but I don't claim to know that for sure. The ones I have found are about one-half to three-quarters of an inch long and are a deep to medium chocolate brown.
These Little Brown Stoneflies inhabit the parts of streams with medium to medium-fast currents where the water is well oxygenated. They cling to the bottom of the rocks and other debris on stream bottoms, which provides protection from the swifter currents.
At times of emergence, the stoneflies migrate to the edges of the stream where they climb out on top of logs and rocks. Some climb out on top of exposed rocks in the middle of the river. When they have climbed to these areas they molt and become winged adults. They then fly to the available streamside vegetation and mate. After mating, the females return to the river to deposit the eggs. As far as I am able to tell, this all happens in the early spring, which happens to be the time I like to fish the artificials.
The few fish I keep in the spring are nearly always filled with small brown stoneflies. At time of emergence, the trout will move into the shallow ripples and take advantage of the helpless bugs that are forced downstream by the current.
Do not concentrate all your fishing in these areas alone. The stonefly nymphs are poor swimmers and are washed into deep pools and runs where the fish also wait for the free meal. I have excellent success fishing the stonefly dead drift on the bottom of large holes and have taken some large trout that were afraid to move into the shallows in broad daylight.
There are quite a few imitations available to the angler. Some are simple and others are complex. A good pattern and a simple one to tie is fashioned after the Box Canyon which is a creation of Mims Barker of Ogden. It is tied exactly like the Box Canyon only it incorporates brown materials and smaller hooks.
The one I like to use is called the Brown Jacketed Stonefly, which uses a small section of brown plastic tubing to form the abdomen of the fly. This pattern really emphasizes the sections of the abdomen, while the rest of the fly is tied basically like most other stonefly imitations.
Some of the other popular patterns are the Early Brown Stone, Birds Stonefly, Kaufmann's Brown Stone, and the ever present Hare's Ear tied in darker tones.
When spring hits, it's time to take out the brown stonefly imitations and get on the rivers. Many fishers head to the famed rivers of Wyoming, Montana and Idaho to catch the fabled stonefly hatches that occur on rivers such as the Yellowstone, Madison, and Henry's Fork. I, too, have followed the crowds, but more and more I am finding that fishing the stoneflies close to home can provide for excellent catches and great fun.
Mims Barker's Box Canyon
Hook: Sizes 2-10
Tail: Black goose quill fibers
Abdomen: Black yarn
Wingcase: Mottled turkey quill
Thorax: Black yarn
To tie the brown version, just substitute brown materials in place of the black and use smaller hooks.
Brown Jacketed Stonefly
Hook: Sizes 6-10
Tail: Brown goose quill fibers
Abdomen: Plastic jacket off 18-gauge bell wire
Wingcase: Mottled turkey or pheasant tail feather
Hackle: Brown, black or furnace
Thorax: Brown dubbing
Ribbing: Stripped peacock
This pattern is a little harder to tie than most imitations, but the effort is worth it.