Brachycentrus
Early April is a quiet time in West Yellowstone. Vacationing skiers and snowmobilers are gone, and the summer tourist hordes are still weeks away. The town belongs to its residents. April is also a time of transition; winter slowly eases into spring, though ordinary measures of springtime such as warming days and greening grass fail dismally as a yardstick in this mountain town. Snow still covers the ground and will do so for the next month. Most locals are heading south in search of a warmer climate. Spring has arrived when you have trouble finding an open restaurant in town, and early April is that time. For fishermen it is also time to begin thinking of caddisflies.
Heavy emergences of Brachycentrus occidentalis (Brack-ee-sen'-trus ox-uh-den-tay'-lis) begin around the tenth of April on the thermally influenced waters of the Madison and Firehole Rivers in Yellowstone Park. This is the first major caddisfly of the year to emerge on trout streams, and it is fed upon readily by the trout. It is a caddis that exhibits considerable sexual dimorphism in size: the females are a full size #14, the males a #16. Both are a choice meal for fish whose main surface foods until now have been small Baetis mayflies and midges. Brachycentrus are dark gray in color, almost black at times, and both sexes have distinct olive-hued stripes on the sides of their gray abdomens. These stripes, combined with the time of year they emerge, is a reliable identification feature.
The emergences of B. occidentalis on the Madison and Firehole are unique because of the thermal influences in the watershed. Brachycentrus is normally an explosive, concentrated emerger, with millions upon millions of individuals emerging over a period of a few days. Instead of these typically quick, mind-boggling emergences, the Park waters experience less intense hatches extended over a much longer period. Fishable numbers can be seen on both rivers from early April until the beginning of July. Yellowstone Park doesn't even open for fishing until Memorial Day weekend, but fishermen can still have a month of Brachycentrus activity.
Brachycentrus occidentalis is also referred to as the "Mother's Day caddis", especially in the Livingston and Bozeman areas, where the nearby Yellowstone and Madison Rivers experience incredibly heavy emergences around, coincidentally enough, the holiday of the same name. Sometime around the end of April or early May is the time to expect this activity.
Fishing during the Yellowstone's emergence depends on the spring runoff situation. The yearly appearance of B. occidentalis and the beginning of spring runoff frequently coincide. If early May is warm and substantial snowmelt begins, the fishing is usually in jeopardy. The Yellowstone can discolor and rise to the point of unfishablility overnight, ruining some prime early season fishing opportunities. But in those years when the caddis appear a little early, or when snowmelt is delayed by cool weather, the fishing can be phenomenal for both trout and whitefish.
The lower Madison's emergence can be fished more reliably, because runoff usually does not begin before the hatch is well underway. On both these rivers, Brachycentrus emerges over a short time period, often lasting barely two weeks, but in much more concentrated numbers than on the Park waters. Both the emergences and the egglaying flights can be spectacular, with seemingly infinite numbers of caddis in the air and on the water. It is not uncommon for huge rafts of spent adults, often inches thick, to build up in back eddies along shore. The best activity is in the afternoon, and the fish will feed readily on both emerging pupae and spent adults. The fish are not difficult to catch, and using a fly that doesn't even resemble B. occidentalis is often the best way to compete with a myriad of naturals for a trout's attention. Downwing attractors like the Royal Trude, which are easily visible but still possess a general caddis silhouette, are good choices.
The Henry's Fork at Last Chance, Idaho, is the only other river in the area where emergences of B. occidentalis are heavy enough to make it a major insect. The emergence there lasts from May 25th until approximately June 25th. This makes it the first caddis of the year to appear, and aside from Rhithrogena mayflies it is the only other sizeable insect present at the end of May.
Most of our fishing on the Madison and Firehole in Yellowstone Park and on the Henry's Fork is done with adult patterns. Brachycentrus are most active in the afternoon and evening, and egglaying and emergence often coincide. Egglaying females sprawl awash on the surface or crawl underwater. The underwater egglayers usually resurface, then flop helplessly as they drift downstream. An adult pattern works well whether the fish are taking egglaying adults or freshly emerged caddis. We have rarely run into a situation where the trout feed exclusively on emerging pupae; even when they do, this early in the season it is still possible to fool them with adult patterns.
One other species of Brachycentrus is worth mentioning, and that is americanus (uh-mare-uh-con'-us). This caddis emerges in August on the Henry's Fork, Yellowstone, and the Madison below Quake Lake. Brachycentrus americanus is sparse on the Madison, and we don't consider it a significant caddis there. They are much more important on the Henry's Fork and Yellowstone, where tremendous numbers are available to the trout. Brachycentrus americanus is a lighter gray than B. occidentalis, but otherwise both species look similar. Sexual dimorphism is evident in their size too; the females are a #14, the males a #16. Egglaying is the most important stage for fishermen, and this can occur anytime during the day as long as the temperature is fairly cool. Generally in August this means early morning or evening, though a cloudy afternoon is ideal also.
On the Henry's Fork we have cast to fish that were lined up behind protruding rocks and logs, picking off egglaying B. americanus as they crawled beneath the surface, laid their eggs, and drifted off with the current. Large numbers of caddis will use these types of site, and the steady flow of naturals is a strong inducement to the fish. Where there are no midstream logs or rocks, the caddis appear to release their eggs at the surface as they hopscotch along. Selected emergences:
- Brachycentrus occidentalis Madison (YNP), Firehole: April 10 - July 4 Henry's Fork: May 25 - June 25 Madison below Ennis: late April - early May Yellowstone around Livingston: late April - early May
- Brachycentrus americanus Henry's Fork: August 10 - August 30 Yellowstone: July 25 - August 30
| Hydropsyche |
| The Madison River below Quake Lake appears at first glance to be a large, fast-flowing, continuous riffle. For many fishermen this is a tough sight to reconcile with the classic trout stream, where shallow riffles separate gentle pools in a regular sequence. The Madison is definitely intimidating the first time you fish it, mostly because the eye is drawn to the river's middle, where heavy, turbulent flows crash around huge boulders.
Familiarity breeds understanding though, and as you spend time fishing the Madison you learn to ignore the middle, concentrating instead on the slower pockets along the river's edges. These pockets, which are small and intimate, are where the most fish are caught. Once this is understood the Madison essentially becomes a study in small stream fishing, and its charms are impossible to resist. The Madison flows some forty miles in the section from Quake Lake to the town of Ennis, bisecting a valley of sagebrush covered bench land. Rugged mountains jut from every horizon, and the highest peaks often hold their snow year-round. On pleasant summer evenings, which are frequent, the river is a fly fisherman's paradise.
An angler onstream during evening hours will discover that the air temperature drops considerably from its midday high. As the mercury falls, the strong afternoon winds do likewise. The last of the fluffy cumulus clouds that build up on most afternoons sail off over the Gravelly Range, leaving in their wake a sky so clear and blue and big it could only be Montana. The Madison turns deep blue too, as the day's last rays of light reflect from the water. Insects flying over the surface and the first riseforms are easily spotted in this evening light.
The trout rise sporadically at first, their feeding rhythms perfectly mirroring the insect activity. As darkness sets in the insect activity intensifies and more trout begin to feed. The feeding increases steadily until, at dark, trout are porpoising regularly in every nook, cranny, and hole available. Choosing just one fish to concentrate on is necessary but difficult. You're tempted to cover a different fish if one or two casts go unrewarded, but this tactic is usually futile. Invariably in these situations, the browns and rainbows are feeding on emerging Hydropsyche caddis.
The various species of Hydropsyche (Hy-dro-sy'-key) are far and away the most important caddis in this area. They are dominant elements in the insect communities of many rivers, and the rises of fish they inspire are Olympian. Of all the stream insects, only the Pale Morning Dun could possibly be more significant.
Heavy Hydropsyche emergences occur on local rivers from the middle of May until nearly the end of August. This lengthy schedule results from water temperature variations in the rivers and from that fact at least four separate species of Hydropsyche make up this hatch. Hydropsyche cockerelli (cock-er-ell'-eye) is the first to emerge each year and is the most abundant. Hydropsyche occidentalis (ox-uh-den-tay'-lis), H. oslari (os'-lair-eye), and H. placoda (pla-co'-duh) follow and comprise the rest of the hatch.
All Hydropsyche species resemble each other, and they can all be considered synonymous from an imitation and fishing standpoint. Adults come in two sizes; #14 and #16 (the females are usually the larger of the two). Adults have tan wings and bodies of light brown, golden-yellow, or green. The differences in body color are apparent only at emergence; a day or two later the bodies of all species will turn light brown. The wings always remain tan.
Fish will feed heavily on Hydropsyche during both emergence and egglaying, but emergence is the major stage. Emergences occur in the evening, and can last for several hours. Their intensity increases as daylight fades, and Hydropsyche can be found coming off well past dark.
Egglaying usually occurs sporadically throughout the day, but there are often peaks in the early morning and early evening. The number of egglaying caddis you can expect to see, even during the peaks of their activity, never approaches those found during the emergences.
The larvae of Hydropsyche build simple retreats to live in, not true cases like other caddis. They construct nets to seine particles of food from the current. Trout no doubt occasionally feed on larvae accidentally caught in the current, but we feel they are not important enough to warrant specific imitations. Evening Hydropsyche fishing generally follows a predictable pattern. We like to arrive onstream in early evening in case there are female caddis egglaying. Egglaying Hydropsyche are easy to see because they fly low over the water and are fairly large. These females release their eggs by repeatedly bouncing on the surface or by flopping and twitching as they drift on the surface.
During this egglaying activity, trout will chase the female caddis readily. Aggressive, splashy riseforms are common in these situations, regardless of the size of the fish. This feeding is purely happenstance and opportunistic because the adult caddis are usually scattered widely. Some fish may see many caddis, other fish will see none. We prefer to fish floating adult caddis patterns during this activity and we limit our casting to rising fish. Doing so avoids disturbing too much water.
Frequently in the early evening, male Hydropsyche from earlier emergences assemble over the water into mating flights. These caddis flights can completely span a river, and often reach a height of thirty feet. Many fishermen confuse mating flights with a caddis emergence or a caddis egglaying period. They are neither. After flying slowly upriver, these flights of male Hydropsyche eventually disperse without ever becoming available to the trout. Even though no fishing results from the flights, it is still an impressive sight to witness.
As evening progresses and the temperature cools, egglaying ceases and emergence begins. The two stages rarely overlap. As trout begin taking emerging Hydropsyche pupae, their feeding rhythm and riseforms change. Dorsal fins and tails often break the water surface as the fish take the pupae right beneath the surface. The rises are deliberate and unhurried. Only the small fish rise aggressively now, at times rocketing themselves completely into the air in their efforts to take the pupae.
Though the trout are feeding primarily on pupae, we do not always fish a pupal pattern. The Iris caddis or X-caddis, which imitate an emerging caddis stuck in its shuck, are two of our favorite patterns to use. These patterns are fished dry, and they sometimes seem to work better than strict imitations of the pupae.
Hydropsyche emergences can last well past dark, and the fish will continue to feed as long as there are caddis available. We have found Hydropsyche emerging as late as 11:30 p.m. in July on the Madison River.
On the Firehole River, it appears that the water temperature influences the behavior of Hydro-psyche. There are spring and fall peaks to the emergence; May, June and October are the best months. Hydropsyche is present but sparse and scattered during July, August, and September.
Selected emergences:
- Firehole River: May 15 - October 16
- Henry's Fork: May 20 - June 25
- Madison River: June 5 - August 15
- Yellowstone River: July 10 - August 24
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