Fly Fishing the Salmonfly Hatch

One of the most famed hatches in the entire world happens each year in early June just a short distance from the doors of Vail Valley Anglers on the upper Colorado River. Unfortunately with this year’s huge flows, we won’t see much action during this hatch. But this season, for anglers heading to other good salmonfly locations, Salmonflies will provide excellent fishing. These big bugs are known as Salmonflies, Giant Stoneflies, or Willow Flies, and their emergence is simply called “The Hatch”. Anglers travel from all over the world to time their fly fishing trip to coincide with the Salmonfly hatch on rivers like Montana’s Madison River or Colorado’s Gunnison River.

The reason is because trout, especially large ones, take notice of these bugs in a big way and their emergence offers anglers a rare opportunity to throw huge dry flies on stout tippet to fish that have lost all caution and eat aggressively.  On the Colorado River, where Vail Valley Anglers guides, the huge bugs come a little earlier than on some streams and so this hatch is a little overlooked by some destination anglers.

Depsite missing “The Hatch” due to the high flows this year in Vail Valley, Salmonflies remain an important year-round food source in our local rivers. The nymphs are present year-round in various sizes and the trout feed on them whenever they are drifting helplessly. Even some small mountain streams like the Piney River have these big insects. Big stonefly nymphs are always a good searching pattern in high-off color water like we have this year.

Salmonfly Decsription

Salmonflies are a large species of stonefly found in cold, clean western rivers. The stonefly nymphs  take three years to mature before turning into a flying adult. They are always available as a food source to trout as nymphs but more so prior to mass emergence in May and early June. Nymphs range from one to three inches long and are darkly colored with black, brown and purple tones.  They prefer rocky riffles of moderate speed and depth.
The nymphs migrate en masse to crawl out of the water onto rocks and especially willow bushes lining the banks, where their nymphal case splits and a winged adult crawls free.  This is unlike many other insects that hatch on the surface of the water before flying off and it is why trout prefer large, dark colored nymphs drifted near banks before the bugs begin flying around.

Adults known as Salmonflies or Willow Flies are two or three inches in length and have an orange or salmon colored abdomen with darker legs, thorax and head. Wings are large and prominent but lay on the back rather than upright. The adults are ungainly flyers and struggle to get and stay airborne, especially if it is cool or windy. When they are blown or fall onto the water, or a female is laying eggs in the water, Salmonflies are very susceptible to predation because they have trouble escaping and create a noticeable disturbance.

Salmonfly Nymph Fly Patterns
Pats Rubber Legs

Simple nymph patterns tend to work best for these insects in sizes #2 through #10 with #6 being a good all-around choice.  Black and brown Pat’s Rubberlegs are a guides’ favorite. The classic Bitch Creek still catches a lot of big trout as does a Girdle Bug. A sneaky choice is a dead drifted black and purple wooly bugger. Expensive, complicated nymph patterns with tungsten beads, miles of flashy materials and hinged hooks catch some trout but because these are heavy flies being fished near or on the bottom close to the bank, it is common to lose flies frequently. Stick with the basics.

Also, to help land heavy fish in current and get flies dislodged from snags, use at least 3X Fluorocarbon tippet but I prefer the added strength and abrasion resistance of 2X. When trout are eating big stonefly nymphs, they are far from tippet shy and that trophy ten pound brown trout is a distinct possibility when there is a salmonfly feeding binge going on. Big, easily caught meals attract big fish!

Salmonfly Dry Fly Patterns
Salmon Fly Dry

Tippet size holds true for adult imitations as well. I try to stay away from truly giant dries in the #2 and #4 range simply because they are tough to cast and the trout seem to have a harder time eating them. A #6 seems to work best as it is plenty even big enough to get noticed, casts and floats well and can be inhaled easily.
I think a meaty profile and body color are important considerations as well as having a low-riding fly. Real salmonfly adults float low in the water. The Noble Chernobyl  Salmonfly is a great choice that is very durable. Big Orange Stimulators seem to work well in fast water. Perhaps my favorite is an Orange PMX in #6.  The Rogue River Stone is also a local’s favorite on the Upper Colorado River.

Don’t to be afraid to wake or skitter your dry fly if a dead drift presentation is not producing. This will often illicit violent takes since actual salmonflies are clumsy and struggle actively when they are stuck in the water.

The Fishing

Before the hatch in May and June, expect to catch lots of fish nymphing as the trout follow the nymph mass towards the banks.  Some anglers pound the middle of choice looking holes and get blanked while others who have noticed the nymphs have all migrated to shallower near shore water will catch one trout after another fishing just a rod’s length from dry land. Trout follow their food sources just like other fish. Wade fishermen can do very well during this period.

When the hatch actually gets underway, stonefly nymph patterns will still produce, especially when mornings are cool. As air temps warm, the adults, which are clustered in huge numbers on branches lining the river, will begin to fly. Now is the time to make the switch to a dry fly.  You will begin to notice splashy, noisy rises. Get that dry fly in the water near the bank! Soft presentations are unnecessary while slamming your fly onto the water mimics an actual stonefly falling into the water.  Float fishing is by far the most productive way to take advantage of this fast paced dry fly fishing.

The really good fishing during “The Hatch” may only last a few days, usually not longer than ten days. At some point, most of the trout will have gorged themselves to the point that the fishing simply slows down. It is not uncommon to catch a trout and be able to feel a crunchy ball shaped mass in their belly-dozens of salmonflies being slowly digested.  After a few days the fishing picks up again. There is always enough stragglers left to keep the trout’s attention for a week or two after the main hatch.

At Vail Valley Anglers we have a huge selection of salmonfly patterns. If you are headed out to chase “The Hatch” on the Gunnison, in Montana or anywhere else stock up at the shop in in Edwards.

Brody Henderson, Senior Guide and Web Content Writer