Fly Fishing Bug Guide: Giant Salmonfly
- Michael Dooley
- May 5
- 8 min read
Spring is here, in Central Oregon, which means salmonfly season along with higher temps and increased runoff in our rivers and lakes. During this time the water temps start to rise and the bugs that dug down deep into the rocks and debris to make it through the winter start to emerge to continue their reproductive cycle that feeds our beloved redband trout.
The Salmonfly, Pteronarcys californica, is the largest aquatic stonefly to call Central Oregon's waterways home and represents a great opportunity for fish to gorge themselves on nymphs and eventually adults in late May and the first half of June. The hatch is dependent on weather and water temps such as any insect so watch the water temps and once they hit 56 degrees the emergence of these large stoneflies is bound to happen.
As a fly angler, it is important to understand the behavior of the insects, when they emerge, where they are, and how to best imitate all the stages of their lifecycle. You can separate these stages into prehatch, hatch, and posthatch. That being said, all of these stages can be happening simultaneously on the same river depending on what section of the river you step foot in.
Salmonfly Stages
The salmonfly's behavior, like many aquatic insects, is dictated by water temperature, which triggers the transformation from nymph to adult. The insect displays various behaviors throughout its life cycle, but as an angler, you want to focus on a few key windows of opportunity because the hatch can happen fast and the bugs will be gone sooner than you hoped.
Nymphal Stage
The nymphal stage of the salmonfly might be the most productive and important time for anglers who are serious about catching fish and don't care if it comes subsurface. About a month before the emergence, which usually starts around mid-May on the Deschutes, the nymphs make the migration from their homes throughout the river to congregate close to the banks in preparation for climbing on the bank and cracking open their exoskeleton.
This is the optimal timeframe to fish a big black or brown stonefly right near the bank. Although stoneflies are a great year-round fly choice because the salmonfly nymphs are always hiding within the substrate, the large movement of the bugs makes them easy pickings for big redbands.
The concentration of food brings every hungry fish right to the bank, including the biggest fish in the river. Some of the biggest fish I've seen come during the salmonfly hatch due to the immense amount of calories along the bank. The nymphal stage of the salmonfly are poor swimmers and are carried through the current to the waiting predators.
Fishing the Giant Stonefly Nymph
When picking a giant stonefly nymph, the legs are the most important physical feature to imitate. The leggy insects tumbling through the water column after being pushed off their rock is an irresistible profile to trout and salmonflies who make up a huge portion of their diet in the spring. The nymph is tapered from head to tail and has a segmented body. The profile is important but the lifelike movement of the legs is a key factor that drives the fish crazy.
The key to fishing a stonefly nymph is to find likely zones where these bugs would clamber up the bank to emerge and get knocked off by a fast current. Fish the edge of strong currents pushing up against banks or shelves that drop off to a nice channel. Don't feel like you need to cast far in these scenarios. The fish push as close to the. bank as they need and a well-presented cast at the feet can produce fish, I have even caught them while absently stripping in my nymph rig for another cast.
Use some weight, no matter if it's a split shot or a weighted fly. Springtime on the Deschutes means high flows make it difficult to adequately reach the strike zone. Use an indicator or tight line nymphs for best results. personally, due to the proximity of the fish and the heavy flies, I prefer to break out the 10ft 3wt.
The color of flies can be an important factor. Golden stones are hatching at the same time as the salmonflies, which means there are plenty of options for color combinations and the fish might prefer one over the other. I prefer black or mottled brown and black but at times I tie on a golden variant or a flashy stone that acts as an attractor.
Additionally, the tapered and segmented body indicates the nymph will wiggle or thrash as they attempt to grapple a rock to slow their downstream progress. By fishing a leggy Wooly Bugger or a TJ Hooker that has "tails" you can better imitate the natural movement of the insect in the water.
Adult Salmonfly Stage
Big foam bugs. Everyone's favorite time to be on the river and for good reason in my opinion. While it can be crowded on the river, the fishing can still be phenomenal but it takes luck, bushwhacking, and determination. The adult salmonfly is the belle of the ball and anglers with no jobs and a car to sleep out of will follow these things as they move up river systems before heading to the next river with the best emergence.
Once the stonefly nymphs drag themselves on the bank they are free to begin the process of molting. They shed their exoskeleton and climb onto an elevated surface to dry their wings and rest from the hard work of surviving the gauntlet of fish waiting for them on the bank.
Then they are alive for a few days to a few weeks with the sole intent of mating; they eat little to nothing and engage in mating flights in the evening before the females move to deposit their eggs in the water meeting the end of their life cycle. But in between emerging and hatching they often will cling to bushes, branches, and tall grass, providing ample opportunity to be eaten by a fish.
Fishing Adult Salmonflys
The adults are big ugly orange and black bugs that love to crawl to the highest point available, so chances are you'll feel them on your neck or see them scurry across the brim of your hat. Fishing salmonflies can be finicky depending on the weather and conditions.
A key thing to note about the salmonfly or stoneflies, in general, is that their emergence is not a water-bound activity, meaning their transformation from nymph to adult occurs on land, unlike a mayfly or caddis that go through this process in the surface film.
The fish are not smart enough to connect the mass migration of stonefly nymphs to the big objects hitting the surface of the water above them, plus why bother eating a few adults when you could continue to gorge on hundreds of salmonfly nymphs?
This means there is a delay in action, the nymphing is good to great, and there are hundreds of salmonflies on the bank, but the fishing will not take a dry despite the abundance of bugs. Chances are you are fishing too early in the hatch and the fish have not keyed in on the adults. If you find yourself in this situation you can try a variety of tactics to encourage a fish to eat.
Change locations
The bugs emerge according to water temperature and the water is consistently warmer lower in the river. The lower, warmer sections of the river will see the earliest emergence and they will work their way upstream. The fish in the lower section have seen more adults and are more eager to take a fly.
Fish Morning and Evening
Like many hatches, the times of dusk and dawn can be the most productive times to catch a fish on a dry fly. The fish are comfortable once the shadows creep across the river and they become more bold in taking a stonefly imitation. Save your dry fly fishing for optimal windows and take a snooze or nymph in the middle of the day.
Target the Right Areas
If the dry fly action is slow and there are lots of bugs that doesn't mean the fish are completely quiet on the surface. Many people attempt to fish the salmonfly hatch by tying on a chubby and long dropper to optimize their fishing but in my mind, it does more harm than good, particularly during tough parts of the hatch. That dropper encourages people to fish riffles and open water that allows the nymph to do its work but actively detracts from dry fly fishing. Instead, I fish a solo dry 90% percent of the time because I can wedge it up under trees, logs, and bushes with no fear of losing my nymph every cast, and let's face it, you can nymph every other day of the year so why do it when salmonflies are crawling on your neck. Most of my salmonfly spots involve some degree of overhanging structure and it isn't easy for clients or myself to cast a clunky dry dropper setup in that scenario. If you want to fish a dropper then fish it short because the fish won't be sitting deep when they are on the bank.
The hatch is on and it is in full swing. You get up early and as you walk down the trail it sounds like cannonballs are falling into the river and as you reach the bank you can see and hear dozens of fish leaping out of the water to take 3-inch-long stoneflies off the surface. This prime window for fishing with salmonflies is usually short due to weather, water conditions, and pressure, or the bugs simply do their business quickly, so make the most of the epic fishing while you can.
During this time you feel like you can do no wrong but it still does not always come easy. Continue to practice creative approaches; bushwhack to get to the water no one else dares to go and change your fly as the fish adapt to the angling pressure and change in food sources. The difference between a stellar day and a bad day during the hatch can be determined by angler effort and targeting fish where you have the best chance at success.
Post hatch the fish are educated, they've seen all the big foam flies and 2x tippet. Now it's time to dial in your dry fly skills with low-profile patterns resembling dead salmonflies or smaller golden stones drifting down the river on the bank. Size down to a 4x tippet for a lighter presentation for the picky fish. Still target the same trees and banks but try expanding to the riffles or seams off islands or points. Opportunistic fish will crush a salmonfly even if it isn't necessarily looking for them. When the female golden stones and salmonflies start to lay their eggs they are vulnerable to predation because they quickly touch the water when depositing their eggs.
Book a Trip During Salmonfly
This is the busiest time of year for guides in Central Oregon, oftentimes, guides fill their books for the 2-3 week stretch of giant stonefly season well in advance, so be proactive when picking your dates. The salmonfly season is busy, so weekdays are best if you want to be around the least amount of people.
Additionally, you can expect an early wake-up call to get on the river before the other anglers. Fishing in undisturbed water early in the morning can make the difference in catching a few on a dry or finding a bunch of hungry fish.
The 2025 salmonfly season is around the corner and I have some prime dates available in the last week of May and the first week of June. The fishing will only keep getting better over the next few weeks as water temps warm. The salmonflies are already hatching below Maupin and soon they will invade our day stretch in large numbers. I also have some dates available from May 11-16th for pre-hatch nymphing or possibly some early dry fly action. I hope to hear from you or see you on the water, tightlines!
Comments