In many ways the hopes and dreams of fly fishers rest on the existence of bugs. Sure, you can venture out onto your favorite piece of water on any given day and catch some fish, many times lots of fish, when there is seemingly no bug activity. But, those aren’t the days that get etched into your memory. Those aren’t necessarily the days that inspire you to make life decisions. Like, say, picking a college that is surrounded by the most prolific dry fly fishing on the East Coast, or, perhaps picking a wedding date in late September which, conveniently, doesn’t overlap with any major trout stream hatches…hypothetically speaking, of course.

Streamer fishing has its virtues; “the tug is the drug”. And, nymph fishing most certainly produces more than it’s fair share of memorable days and 3-dimensional challenges. But, nothing in our sport tops the visceral experience that is watching a body of water come to life with an exuberance of bug activity, and the ensuing trout feeding frenzy. In my opinion, nothing illustrates that better than a Callibaetis spinner fall on western stillwaters.

Callibaetis mayflies have a massive distribution across most of North America. It is the western subspecies (Callibaetis ferrugineus hageni), though, that produces inspirational fishing on countless lakes, and several notable rivers, in the Rocky Mountain West.

Callibaetis mayflies live in stillwater environments. They thrive in water that has rich weed growth. And, while the emergences are often inconspicuous, the spinner falls are the stuff of legends.

Callibaetis mayflies, along with their diminutive brethren Tricos and Midges, are responsible for the legendary “Gulper” fishing that happens on Hebgen Lake each summer from late-July to mid-September. The shallow, weedy arms of Hebgen Lake are such ideal habitat for Callibaetis mayflies that they produce an awe inspiring amount of insects. Dense spinner falls occur here, and trout rise to the spent adults with such rhythm and regularity that you can hear the fish rising with an audible gulp that resonates across the glass flat waters.

Warm, calm mornings are ideal conditions for these size #14-16 speckle winged mayflies to form mating flights. It is impossible to miss them when they are around as seemingly billions of adults will dance above the water in a rhythmic undulation. When it is good, and it often is in Big Sky Country, spinners will blanket the water, and everything on the water, including fishermen.

Callibaetis spinners are unmistakable due to the unique speckled blotches present on only the leading edge of their fore wings, and their two long, widely separated tails. Their bodies range in color from brownish-olive to tan to light grey with a majority of spinners displaying a lighter tanish-grey coloration on the bottom of their abdomen and a darker, blotchy charcoal color on the top.

Here are Three Geeky Bug Facts about Callibaetis that will help you catch more fish.

 

1. Callibaetis are Multi-brooded

When we think about the life cycle and seasonality of mayfly hatches, we generally reference a particular bug with its spot in the seasonal lineup of hatches. Certain bugs, like March Browns, hatch in the early season, and they are followed by summertime hatches of PMDs, and autumn hatches of Mahogany Duns, etc. These hatches occur at roughly the same time every year with the progeny of those hatches growing and developing in the river until the following season when it is their turn to complete the cycle.

There are certain bugs, however, that breed multiple times during the course of the fishing season. Like their cousins the Baetis (Blue Winged Olives), Callibaetis will begin hatching early in the season (June in Big Sky Country), and those early bugs produce the ones that we fish later in the season. Also, like their Baetidae cousins, the size of individuals decreases with each brood of the season. Spring hatches of Callibaetis can have duns as large as size #12, whereas September emergences will produce size #16.

Early hatches of Callibaetis are often available in fishable numbers far earlier than when we begin paying attention to them. Unfortunately, the unsettled early season conditions of June in the Rockies don’t often produce dense mating flights of spinners, or the glass flat lake surfaces required for dry fly fishing.

Most years, those early season emergences go largely unnoticed, and it is their offspring that draw our attention later in the summer when weather conditions are more conducive. The warm, calm mornings of mid-summer in Big Sky Country provide both the perfect environment for massive flights of spinners and the glass flat waters needed to bring hordes of trout to the surface.

While average June conditions are generally not optimal for Callibaetis spinner falls, it’s important to remember that the bugs are still active. Duns will continue to emerge, sometimes trickling off one at a time, randomly throughout the day. On the rare day in June, when conditions are cloudy and calm, emergences can be concentrated, and provide outstanding dry fly fishing with duns. The occasional warm, calm morning in June can also generate a fantastic dry fly session with Callibaetis spinners. More often than not, these early season spinner falls are sparse, providing just enough food on the surface to get fish hunting on top, but not so much that your fly is competing with hundreds of naturals for the attention of gulping trout.

2. Callibaetis Nymphs are Strong Swimmers and Fast Emergers

Callibaetis nymphs are a perfectly evolved product of their weedy, stillwater environment. Their bodies are slim in profile with feathery gills, and pronounced variegation on their tails. Coloration ranges from light olive to tan, or gray.

Callibaetis nymphs are agile swimmers, dashing from one weed tendril to the next with short, powerful bursts of speed. Frequently, nymphs will pause for a brief second between sprints, hanging motionless in the water column with their abdomen hanging down. This choreography is important to imitate when fishing Callibaetis nymph imitations. Short, swift strips of 4-6” with a definite pause between movements is the best retrieve as fish will commonly pounce on the fly at the pause.

Just as they move through the water with speed and momentum, Callibaetis nymphs emerge into duns quickly at the water’s surface. It’s common for the nymphs to make several trips back and forth to the surface in preparation to emerge, but once they commit to the meniscus and break through the surface tension, they make quick work of the act. During these “practice runs” the nymphs are prepared to make their quick escape at the surface with fully formed wings bulging beneath their dark brown thoracic carapace (wing pad).

For more great info about Callibaetis nymphs check out this great Callibaetis Nymph Article from our Blog archive written by our very own fanatic of all things stillwater, Matt Klara.  

3. Callibaetis aren’t just found in Lakes

Callibaetis mayflies may be the most infamous stillwater hatch, and Big Sky Country is home to some of the most legendary spinner falls of these speckle winged mayflies.

Hebgen Lake, outside of West Yellowstone, MT, is ground zero for the notorious activity known as Gulper Fishing. Named for the nail biting sound that echoes across the glass flat waters of Hebgen’s weed-laden arms and bays as large trout gulp Callibaetis spinners from the surface, Gulper Fishing is an annual pursuit that rivals the most celebrated spectacles in Fly Fishing.

As epic and addictive as Gulper Fishing is, it’s not the only Callibaetis game in Big Sky Country. The same slow water environments that harbor fantastic populations of Callibaetis on lakes also exists on several of our most legendary rivers. The Henry’s Fork of the Snake River, the Yellowstone River in YNP, and the Missouri River all boast substantial populations of these speckle winged mayflies.

When Callibaetis are found in riverine environments, they aren’t present in the same abundance as stillwaters. Emergences and subsequent spinner falls are generally sparse in comparison to the activity seen on legendary waters like Hebgen or Yellowstone Lakes. What Callibaetis lack in numbers on rivers they more than make up for in the influence they have on feeding fish. When Callibaetis are present on rivers like the Henry’s Fork and Missouri, they are usually the largest bug around at that time, and trout go way out of their way to feed on them.

Now Get Out There and Find Some Callibaetis Mayflies

If you haven’t experienced the thrill and suspense of fishing to cruising gulpers on a warm calm morning in Big Sky Country, do yourself a favor and explore one of the many still waters in our region during Callibaetis time. Remember, Callibaetis will be active as early as June when conditions permit. The bugs will be larger (size #14) in the early season, and later broods will be smaller (size #16). If you fish the nymph imitation, do so with short, brisk strips of 4-6”, and be sure to pause between strips. And, don’t forget to have some Callibaetis dun and spinner imitations when fishing the Henry’s Fork, Missouri and Yellowstone Rivers (in YNP).