Stonefly Hatch – Make Sure You Catch It

stonefly hatch
Stonefly in Stillwater Creek Photo credit: Roger Tabor (USFWS)

For many fishermen catching the stonefly hatch is like the search for the Holy Grail. Either they arrive before the hatch has kicked off, or they hear the adage, “You should have been here yesterday!” Often the fish are too full, or they just have not seen enough bugs yet. There are many “reasons” for the lack of success with this hatch, but for those that have experienced real stonefly action, there is little in fly fishing that can come close.

In rivers where stoneflies are abundant, the hatches that they produce constitute the most crucial food supply that contributes to the growth of trophy trout. Fishermen who understand these hatches can capitalize on the single most significant time of the year to catch large numbers of big fish.

Types of Stoneflies

There are four major types of stoneflies found in the western waterways; 1) Salmon Flies, Pteronarcys Californica 2) Large Golden Stones, Acroneuria Californica 3) Yellow Sallies, Alloperla Pallidula 4) Skwallas, Alloperla delicate. All are important for the fish and the fisherman. They hatch at different times on different waters, opening up a large window of opportunity to “catch the hatch.”


Photo Credit Marcin Chady

The giants of the aquatic insect world, these are the bugs that most fishermen think of when their thoughts turn to stoneflies. Salmonflies start to hatch on most rivers as soon as the runoff subsides and water temperatures stabilize in the mid 50 degrees. When the timing and temperature are right nearly all the bugs in a given section of the stream will emerge within a 4 or 5 day period. This will begin on the lower parts of a river and work its way upstream over a time of 10 days to 2 weeks. Timing is crucial for this hatch. A day early or late, on a given section, can make a huge difference. For instance, fishing on the upper part of a river may be slow due to the hatch not arriving yet, but on the same day, the lower section is red hot. Talk to the guides and outfitters in the area to get the most up to date information available.

Large Goldenstones

golden stonefly
Photo Credit gailhampshire

These large stones are slightly smaller than their cousins the salmon fly, but not by much. Where a salmon fly would be a size #2 or #4, a large golden is from #4 to #8. While these bugs begin to hatch just as the salmon flies are waning, their emergence lasts much longer on most streams and is in reality more important to the fisherman. Goldenstones do not hatch all at once as salmon flies do, in fact, on some western streams their emergence can last through mid-October! Hatching in smaller numbers means that trout do not get tired of seeing them, as they can with the salmon flies. It is always a good idea to try a golden stone pattern during the salmon fly hatch. Trout often like something new or different in color or size. When this is the case, a big Golden is always a good idea. Large golden stones are the favorite food of trout.

Yellow Sallies

Much smaller than the golden stones or salmon flies are the yellow sallies. In sizes, #10 to #16 these little bugs pack a big punch. Sallies often begin emergence with or before the salmon flies hatch, and can continue hatching for a few weeks after the big bugs are gone. They are sometimes known as Red Tags, because of a red mark on the end of the abdomen, which is not present on all Sallies. Color can range from bright yellow to light olive to brown or dark olive. These small insects are easy prey for many trout and can produce large numbers of fish on a given day.

On spring creeks and flat water streams, such as the Railroad Ranch section of the Henry’s Fork, Sallies can be particularly exciting. As trout in these streams feed quietly in rhythm on PMD’s, there is no question when a sally enters the fishes view. Explosive feeds can be witnessed as these ordinarily selective, graceful beauties of the spring creeks throw caution to the wind and attack one of their favorite foods. Even if the Sallies are not out in great abundance, trout will pounce upon them.


Photo Credit Andrew C

This lesser known and lesser distributed stonefly hatches early in the season, long before most anglers dream of dry fly fishing. As soon as mid-March and through May these mid-sized stones will hatch on select streams. The Bitterroot Valley of Montana has some of the most prolific and well know of these hatches. Skwalas range in size from #8 to #12 and are olive in color. These bugs provide an excellent opportunity to fish large dry flies very early in the season.

Due to the unpredictable weather during this early season, it is essential to watch forecasts and plan trips around warmer weather. Skwalas, like other adult stoneflies, do not like to fly during cold weather. Look for sunny conditions and temperatures around 50 degrees when planning a skwala trip.

Stonefly hatch fishing tactics


Much is made of the “dead drift,” but in some cases, this type of presentation will produce nothing more than a dead day of fishing. Stoneflies are big bugs with big wings, and only one purpose in life, reproduce. The life cycle of these insects lasts up to three years, just about ten days of which are above water. In this narrow time frame, they hatch, mate and lay their eggs. In short, they are in a hurry and thus create a lot of movement upon the water. Many times they are seen skating across the water in an attempt to reach the shore or drop their eggs in the current. Often they are seen dive bombing the water from twenty feet in the air to dislodge the egg sacks and keep the circle of life going. In any case, stoneflies move, a lot.

To entice large trout to an artificial stone anglers should similarly work the flies. Delicate casts are not the order of the day here. Cast the fly hard, so that it slams the water making a commotion. This will not scare the fish but rather attract them. Pounding the bank is a term often used by guides to instruct their fisherman to cast in such a manner.

Twitching is also a relevant and useful technique when fishing the big bugs. Twitching is performed by retrieving the fly in such a way that it appears to be skating on the water. This is done by jerking the rod tip to the side of the body then retrieving the slack line and repeating until the strike occurs or it is time to recast. Both of these tactics can be very effective and produce explosive and exciting action.

Double Fly Rigs

Fishing two dry flies can be a lot of fun as well as efficient. Tandem rigs are most often thought of as a dry dropper set up, but during the stonefly hatch, in particular, fishing all dry is much more fun. Using two dries can help in many ways.

  • First, by fishing two different bugs at the same time cracking the feeding code can be done twice as fast. Sometimes two or three various stoneflies will be hatching simultaneously, but the fish are keying in on only one of them. Fishing two flies makes the job of finding out which one that is much quicker.
  • Second, by fishing two flies separated by two to three feet, an angler is able to work two different feed lines at the same time. This approach is advantageous when fishing from a drift boat, and fisherman only has one chance at a particular bank. With this tandem rig, the inner bank feed line and the outer edge can be worked simultaneously.
  • Third, if the fishing is truly outstanding, it is not out of the question that an angler would pull in two fish at the same time. A scotch double, as it is called, is never anything to sneeze at, but being done on dry flies is awesome. Fish two dries and have twice the fun!

Water types

When reading the water during the stonefly hatch, thinking outside the box can pay big dividends. As fish look for food, they are very economical. They perform a cost-benefit analysis. The cost is the energy a trout will use to catch its prey, and the benefit is the nourishment that said victim would provide. Any time stoneflies are part of the equation the interest is very high. 1/3 of a trout’s yearly weight gain will occur during the stonefly hatch. Because of these facts, trout will work very hard to gain the benefits of feeding on these insects.

Anglers need to open their minds to fishing heavy water, especially when targeting trophy trout. In rivers with swift currents and pocket, water one should never overlook large rocks in the middle of the river, quick outer feed lines or even the fastest banks on the river. These spots can go ignored when there are hundreds or even thousands of salmon flies lining the picture perfect softer banks.  The reality is that in most cases, the heavier the water, the better when it comes to stoneflies.

Sunken Dry Flies

This sounds like a contradiction in terms, but it is not. When adult stones reach the shore, they are frantic to begin matting. They scurry around on the rocks and vegetation in search of a companion or two and many time fall in the water. They get knocked in by fisherman walking down the bank, by cows grazing in the pasture, or by a moose crossing the stream. In any case, the adults get washed away by the current, and many times this occurs in very swift water. The bugs get taken below the surface to the eager trout waiting to eat them.

For fisherman to capitalize on this misfortune, the dry fly must be sunk. This can be done quite quickly. Take an undressed dry fly and submerge it in water. With the fingers press firmly on all the buoyant areas of the pattern, the yarn, dubbing, and wing. When the fly is saturated with water, it should sink just enough to mimic the sunken stone. In cases where the bugs are descending deeper try adding a split shot to the head.  Fishing the sunken dry fly can produce significant results especially when there are vast numbers of dries lining the banks, like during the salmon fly hatch.

Successful Stonefly Patterns

No other dry fly has produced more imitations than the stoneflies. Every angler has his or her favorite pattern and the stories of success to go with it.  Over the years some designs have stood the test of time, producing results throughout the west. Others, for one reason or another, find a home on a particular river. And still today, with an ever-growing number of fly tiers, killer patterns are produced annually.

When designing your fly, it is essential to think of the application. What are the bugs doing? Are you going to be fishing a hot sunny day in the middle of the hatch, when the bugs are flying and diving? Maybe the day will be cool and late in the hatch when the bugs are nearly lifeless and riding low in the water. For every situation, there has been a pattern devised, but this does not mean they can not be improved.

It is also essential to keep a well-stocked box of a wide variety of flies. Even though the trout are feeding on salmon flies, they may key in on a particular pattern. Don’t ever be afraid of changing flies. Do it often. Do it until you are catching fish as you have always dreamed because that is why we fish the stonefly hatch.

Here are a few favorite stonefly patterns:

  • Berry’s Hedgehog
  • Berry’s South Fork Salmon Fly
  • Rouge Golden
  • Lawson’s Henry’s Fork Salmon Fly
  • Berry’s Para Sally
  • Mercers Sunken Salmon Fly

Stonefly Hatch Locations

  1. Henry’s Fork of the Snake
  2. Teton River
  3. South Fork of the Snake