Tips for Chasing Montana's Salmonfly Hatch

Tips for chasing Montana's Salmonfly Hatch

By Brian McGeehan | Montana Angler Fly Fishing | www.montanaangler.com

Photo courtesy of Montana Angler Fly Fishing

Montana’s rich and varied wild trout fisheries offer anglers year round fishing opportunities. While it is difficult to elevate any one time of the year as the “best” time to fish the Big Sky state’s blue ribbon rivers, there is no doubt that the most anticipated time of year coincides with the emergence of the legendary salmonfly hatch.

Salmonflies, which derive their name from their salmon orange abdomens as adults, are the largest aquatic insects found in our local rivers. They are a type of stonefly that are found in rocky and swift flowing rivers and are part of the Pteronarcys genus. Salmonflies dwarf most other aquatic insects and often exceed 2 inches in length. It is the large size of the insect that garners so much attention from fly fisherman. While smaller trout will spend their day hunting much smaller morsels of food; large trout tend to eat large meals less frequently. Most of the year anglers in search of truly large trout need to fish subsurface patterns such as streamers that imitate small fish. The salmonfly hatch is one of the rare times when even the largest fish in the river will be tempted to feed on the surface to intercept the oversized adult insects.

As juveniles salmonflies spend 3-4 years as immature nymphs in the river before hatching into adults. Although the nymphs can be a year round food source, they become much more accessible to trout just before the emergence when they migrate towards the banks.

Salmonflies begin hatching in lower elevation rivers that warm faster such as the Smith and as late as mid July on the Upper reaches of the Yellowstone River inside of Yellowstone National Park. Although the hatch can be encountered in different rivers over the course of several weeks, on any one section of river they are only on the water as adults for a few days each season.

Salmonflies prefer a specific habitat within Montana rivers. They require clean, cold, well oxygenated water. They are always found in the most abundance in swifter sections of rivers that are home to large boulders vs. finer gravel associated with lower gradient sections of rivers. >>

TIP 1: DO YOUR BEST TO TIME THE HATCH

One of the most important elements when fishing the salmonfly hatch is to actually find the hatch. Because the insects hatch in such a short emergence window on any one stretch of river they can sometimes be difficult to find. To complicate matters, each year the insects can hatch at a slightly different time during the season. Generally on higher water years when water temperatures remain cold longer the emergence is delayed while on lower water years the hatch begins earlier. What is generally the same from year to year is the relative order of where the hatch is found. The hatch often makes its first appearances in Montana waters in the Smith River canyon in mid to late May. In early June expect to find them on the Lower Madison below Ennis Lake and then in Mid June they hit the Big Hole. Generally the Upper Madison and Upper Yellowstone in Paradise Valley will see salmonflies in late June or early July. The last appearance is generally on the Yellowstone River inside of Yellowstone Park. Salmonflies generally start on the lower reaches of a river where waters warm earlier. Once the hatch first appears it tends to move up river day by day once the colder headwaters warm up.

TIP 2: PAY YOUR DUES AND PUT YOUR TIME IN

Just because you find the salmon flies hatching doesn’t mean you will be catching lots of big wild trout. Most of the time you actually catch fewer fish when chasing salmonflies. The insects are so large that fish can often get full on them resulting in a lower catch rate. The real allure of fishing over the salmonfly hatch is the potential for catching really large fish. Even though you are always in the game for one of the biggest trout in the river doesn’t mean that it will happen often. If you want to catch a really big trout on a salmon fly dry fly you need to invest a lot of time chasing the hatch. When that one special monster finally inhales your size 4 dry fly all the hard work pays off!

TIP 3: FISH BEFORE AND AFTER THE HATCH

Some of the most consistent fishing when chasing tends to occur a few days before the hatch begins and then a few days after it ends. Leading up to the hatch the huge nymphs begin migrating into shallow water where they will eventually climb out onto rocks and grass along the banks to molt into adults. During this nymphal migration big trout will be on the hunt and the subsurface nymph fishing can produce big results.

A few days after that hatch can also be very productive. It can take a few days for fish to digest after a gluttonous feeding spree at the peak of the hatch. When trout go back on the hunt they still remember the big bugs even though they may not be on the water. Fishing a big dry fly a few days after the hatch has moved on can often produce consistent results and larger than average trout.

Chasing the salmonfly hatch isn’t for the faint of heart. The “big bug” often attracts lots of other anglers and there will be many days with huge insects flopping on the water while the trout below are already full and not feeding. Some days you will gear up to chase the hatch only to find lots of other anglers and no salmonflies. Chasing the hatch will most certainly result in numerous points of frustration and disappointment but if you keep swinging for the fences sooner or later you might just hit a home run!