The U.S. West's annual salmonfly hatch is one of those things you have to see to believe. For some, it is more of a myth, as anglers head to the river in earnest, only to find a quiet stretch of river. But when the hatch is on, it is truly an unforgettable experience: hundreds of massive nymphal shucks left behind on rocks, trees, and river foliage, as finger-length adult stoneflies crawl and buzz about.
Soon they are landing on the river's surface in a fluttering panic and what follows is a buffet bonanza for fish, birds... and anglers. The reality is, if witnessing a big trout hammer a size 4 foam fly doesn't get your blood pumping, fly fishing might not be for you.
Salmonfly Characteristics
Out of all stoneflies, the salmonfly is the largest, reaching upwards of 3+ inches in length. As nymphs, they prefer well-oxygenated flows, taking up residence beneath river rock and boulders for roughly three years before moving onto their next stage of development. Once ready and conditions are optimal, the salmonfly crawls up the bank in search of higher ground and molts into their adult form, leaving behind massive stonefly husks that make for an easy sign of an ongoing hatch.
Aside from its size, salmonflies are easily distinguished by their coloration: they are dark brown to black with a burnt orange underside, and a set of flat-lying wings with pronounced veins. They have two visible areas of orange at the base of their wing and behind their head, with a set of large antennae.
Timing the Salmonfly Hatch
Although the fishing season starts well before the salmonfly hatch, it acts as a sort of starting gun for a series of big hatches and the best fishing months of the year. The annual emergence of the massive stonefly brings many out-of-state anglers to the west in hopes of hitting the lotto, while whispers of their first emergence are tightly held secrets amongst circles of local anglers.
The salmonfly hatch is relatively short-lived compared to others, and the start of it varies from river to river. Hatches traditionally move upstream a mile or two each day, but this isn't a hard-fast rule, so where you might expect to find salmonflies in the days to come isn't always reality. At the end of the day, historic trends, word of mouth, and a bit of luck all play a factor in timing the hatch.
Yellow Dog U.S. West Program Director had this to say on the timing and progression of the salmonfly hatch:
"One of the big of factors of when a hatch is going to start is the water temperature, with the magic number around 55 degrees. That can be a double edged sword because any major weather event can put a lull in the hatch, postpone it, or stop it altogether. A lot has to align to hit it perfectly.
Usually one of the more popular rivers to first see a salmonfly hatch is the Henry’s Fork. That can start as early as the second or third week of May, work its way up river, and finishes up around the first week of June.
The next major rivers are the Big Hole and the Blackfoot. Their salmonfly hatch starts around the second week of June and can last through the end of June.
Then comes the Madison. I’ve seen it start as early as the end of June, but more historically starts during the first week of July. This applies to the South Fork of the Snake and the Yellowstone as well, and lasts as short as a week or upwards of three weeks. My first full summer here we had a big water year and I was fishing salmonflies in August, but that was an abnormal year.
The bottom line is if you want to hit it, you have to be on the water."
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Salmonfly Tactics
The combination of the salmonfly hatching along the river's edge and their clumsiness make targeting the bank a safe bet. Don't let that stop you from working holding water, but spend the bulk of your time casting along the edges.
An important element of any hatch is that trout will be feeding heavily on nymphs prior to a hatch, and with salmonfly nymphs offering big, easy meals, trout will be cuing up to feed. Fishing two stonefly nymphs or a dry-dropper at the early stages or before any adult salmonflies are visible can be super productive.
With that said, the truly exciting part of the salmonfly hatch is watching large trout slam a size 4 foam fly. Dry-dropper will very likely pick up more fish, but fishing a single dry gives you better casting precision along the bank.
Jake Wells states, "Sometimes a dry-dropper setup can get in the way and that extra foot can really make a difference. If I can get a foot tighter to the bank with just single dry, I’d rather not have a dropper. Focus on the bank, from five feet all the way to right on it.”
The hatch generally progresses upriver, so use this to your advantage. If you hear or know of bugs hatching in one area, consider heading upstream to catch the hatch in its infancy. Fish will be far more opportunistic at this time as they aren't yet engorged on salmonflies. More than a few anglers have been left disappointed as they catch a monstrous hatch, only to find the fish are already full and shut down.
In addition to catching the hatch early, some of the best fishing can come once the hatch has slowed or stopped altogether. The bug's profile will still be fresh in their minds for upwards of two weeks after the last of the salmonflies. This can even be an more productive time for anglers, as trout are no longer feeding on a steady flow of big bugs and are once again more opportunistic.
While fishing, give your fly some action with twitches or skating the fly. Salmonflies do not land gracefully, but frantically flutter and swim back toward the bank. Use this to your advantage!
Finally, a little pro tip from U.S. West Program Director Jake Wells:
"Golden stones are also hatching around the same time, so it can be more productive to fish a golden stone pattern. The fish have been steadily feeding on Big Macs and another salmonfly is too much -- but a golden stone could be just what they need."
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Top Salmonfly Dry Flies
1. Chubby Chernobyl (Pteronarcys)
Yes, the chubby is a no-brainer. As one of the most popular stonefly/terrestrial patterns ever created, its a good idea to have some in the box. The pteronarcys chubby doesn't have as realistic a profile as some others, but works great before fish have seen a lot of salmonflies or as an attractor pattern. If you don't have the exact pteronarcys varietal, a chubby with orange dubbing and a black or brown foam body works fine.
2. Water Walker
Will Dornan's water walker is a favorite stonefly dry fly for many western anglers, and comes in a number of styles. The bright orange underbody on the chubby chernobyl can be a bit much to fish that have seen a lot of salmonflies, but the water walker's abdomen is darker with just hints of orange for a more natural coloration. Combine this with the fly's wing profile and well-positioned knotted rubber legs and you have a super realistic and productive bug.
3. Morrish Stone
Technically, there are two Morrish stoneflies -- a fluttering and a still stone. Choosing a winner between the two is tough as they are both excellent patterns for different scenarios, so we're including both. The fluttering stone's wing is tied with deer hair, and combined with a big foam body, this fly can float with the best of them.
If the fluttering stone isn't producing during the hatch or you are fishing after its peak, opt for a still stone. The still stone does away with the deer hair and uses a synthetic material for the wing. The result is a wing that that lies flush with the foam body, accurately imitating a spent salmonfly for easy pickings.
4. 64 Impala
The 64 Impala was designed with selective fish in mind after gorging on salmonflies for a few days. After seeing enough salmonflies, a big, colorful chubby will likely no longer do the trick as the trout have learned from the error of their ways. True to its name, the 64 rides low in the surface film, a trait that often produces more fish. The 64 Impala doesn't have a dramatic bushy wing like some other, but an orange foam sighter on top of the flymakes it easy to track in turbulent water.
5. Morningwood Special
The morningwood special is an excellent salmonfly/terrestrial crossover, and can easily support a heavy dropper. While you aren't going to opt for the morningwood special for discerning or picky fish, its an excellent attractor pattern or searching fly when covering water. If you aren't picking up any fish, bring along a brown sharpie and color up the bottom of the fly -- a trick that often translates into more fish!
6. Henry's Fork Foam Stone
According to U.S. West Program Director Jake Wells, this is the only fly you need for the salmonfly hatch. Tied by fly innovator Mike Lawson on the Henry's Fork, this fly is responsible for bringing some of the most discerning trout to hand. Lawson suggests fishing this one high and dry to start, but if the fishing gets tough, don't be afraid to trim the wing down and have it float more flush with the water's surface.
7. Rogue Foam Stone (Giant Orange)
The Rogue Foam Stone is a super realistic fly that is also highly durable. It stands out from the others with its signature bullet deer-hair head, and combined with a natural flat-lying wing and ribbed extended body, this is a fly that continues to deliver. It also comes in a golden stone imitation that you should absolutely have when fishing during late Spring/early Summer.
8. Pat's Rubberlegs
We had to include a nymph. While far less exciting than fishing a single dry, a Pat's rubberlegs will get it done year-round whether salmonflies are hatching or not. Pair a size 6 or 8 Pat's Rubberlegs 1.5 feet below an attractor dry and cover water before the hatch kicks off, or opt for this approach when the fish are no longer readily rising to dries. If the conditions and timing for a hatch are close, start with a Pat's!
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