Understanding Caddis

In last week’s email newsletter I mentioned this article. I finally tracked it down and want you to be able to read it through in its entirety. I think it will shed some light on what’s happening out there on the water. Hope you find it helpful.

Understanding Caddisflies

When John Juracek and I wrote “Fishing Yellowstone Hatches” in 1992 we said that caddisflies are the insects least understood by fly fishers. Today this still seems to be the case despite all that has been written about these insects. Caddis are arguably as significant to anglers as are mayflies, and a knowledge of basic caddis habits is essential for success during the season. It is mostly caddis emergences that puzzle fly fishers, and being able to recognize when caddis are hatching is the first step in understanding caddis.

In his wonderful book “Caddisflies”, Gary LaFontaine notes three signs that indicate when caddis are emerging. First, trout are seen leaping in the air. He maintained this happens when trout chase emerging caddis pupae and the trout’s momentum carries it out of the water.

Secondly, there are no caddis on the water. Even during a heavy emergence adults are nearly impossible to see on the surface. Caddis usually emerge and fly off unnoticed.

Third, LaFontaine felt that most feeding trout are bulging and splashing. Fish taking pupae cause these rises as they take pupae from the surface film and turn downward. While this is often true, we feel that the riseform depends more on the current speed the fish is rising in. In fast water bulging and splashing occurs while in slower water you will see quiet dimples, porpoise rolls, or tails breaking the surface. It is important to consider the riseforms in deciding what a trout might be taking, but it is wise never to make a judgment based solely on it.

No doubt that the strongest clue to a caddis emergence is that no insects are seen on the water, and yet fish are rising. This is a dead giveaway that caddis are hatching.

During caddis emergences I’ll fish two types of dry flies; a caddis pupa and an emerging caddis. Depending on the species, on type works better than the other. Recommended fly patterns are listed under each caddis at the end of this piece.

On pocket water stretches of rivers like the Madison, Yellowstone, Henry’s Fork and Gallatin I approach feeding fish straight upstream. The best way to fish your pattern is dead drift to avoid casting across mixed currents. And, the larger trout always prefer a dead-drifted fly. Also, you can get much closer to rising trout in pocket water by approaching from below.

Caddis emerge best in the evening and after dark. You can get close to rising trout to keep track of your cast when visibility is poor. And, I like to fish a fixed line and adjust my position in relation to the rising trout. This way, I know where my fly is at all times.

If I am fishing spring creeks or smooth water I might position myself to cast downstream and across to rising trout. Generally, I’m further from trout rising in smoother-quieter water and down and across is sometimes best for achieving a drag free drift. This angle keeps me from having to cast the leader over the rising fish. This is not a problem in pocket water because the water is already disturbed. Bad presentation in smooth water usually results in a spooked trout.

Some caddis species bring fine fishing opportunities during female egg-laying. This is accomplished by several methods including bouncing and skittering on the surface, crawling underneath the water, or floating flush on the surface like a mayfly spinner. Here again, as with emergences, there are keys to recognizing egg-laying activity.

Anglers usually think that when caddis swarm in the air that an emergence or egg-laying is occurring. This is not the case. These caddis flights are often swarms of males moving up the river. There is no correlation between them and emergences or egg-laying. Egg-laying is recognized by watching the water of bouncing adults, finding spent females on the water, or checking grassy banks, rocks, or logs that protrude from the water. It is these areas that give underwater egg-laying females access to the water, and they will swarm and collect on them.

Egg-laying caddis are best imitated by dry patterns presented dead-drift. Even though natural caddis might display lots of movement, my experience shows that the larger trout prefer a dead-drifted fly.

Notes on six caddisflies most important to fly fishers visiting Yellowstone country

Brachycentrus caddis have two emergence times in this area. The first begins in late April on rivers like the Yellowstone near Livingston, Mt. and the Madison below Ennis. Mt. The second hatch occurs in late summer on the Yellowstone and Henry’s Fork during August.

The spring Brachycentrus sp.is the Brachycentrus occidentalis. It is often referred to as “The Mother’s Day Caddis” due to its heavy emergences coming off around the same time as the holiday of the same name.

Heavy emergences on the Madison and Firehole Rivers in Yellowstone National Park are in full swing when the fishing season opens in the park the Saturday of Memorial Day weekend. This is the first caddis hatch of the year to emerge and is fed upon readily by the trout. The caddis exhibits considerable sexual dimorphism in size with females a full size #14 and males #16. They are dark olive bodied with wings of dark gray to black.

Trout feed readily on emerging pupae and egg-laying females. These caddis are most active in the afternoon and early evening when emergences and egg-laying coincide. An adult pattern works well whether the fish are taking emergers or egg-layers, this early in the season you will fool them with adult patterns.

The summer Brachycentrus is the americanus. This caddis comes off in August. It is important on the Henry’s Fork and Yellowstone and looks like B. occidentalis. Egg-laying is the most important stage and this can occur in the early morning or early evening.

Big trout like to line up behind rocks and logs and pick off egg-laying females as then crawl under the surface, lay their eggs, and drift off in the current.

The best fly patterns to have are #14-#16 X or X2 Caddis. These two flies are great emerging caddis patterns for all caddis.

Hydropsyche caddis are the most important caddis in Yellowstone country. Their emergences occur on our rivers from mid-May to mid-October.  On the Firehole you will find this caddis from opening day in late May to early July and again in September and well into Ocotober. On the Henry’s Fork from late May through June. On the Madison from early June until mid-August and on the Yellowstone from mid-July through August.

\           There are four separate species that make up this hatch but since all species resemble each other they can be considered synonymous from and imitation and fishing standpoint. (Hydropsyche cockerelli, occidentalis, oslari and placoda comprise the hatch).

Adults are size #14-#16 with tan wings and bodies of light brown, green or a bright amber-yellow. The body color differences are apparent only at emergence, a few hours later the bodies of all will be light brown.

Emergences of this caddis is the major stage trout feed on. The hatch occurs in the evening, and can last for several hours coming off well past dark. I’ve fished emergences until 11:30 p.m. in July on the Madison River and the caddis were still coming off when I left the river then.

Evening Hydropsyche fishing follows a predictable pattern. I arrive onstream around 7 p.m. in case there are female egg-layers. The egg-layers are easy to see because they fly low over the water, are large, and repeatedly bounce on the surface to release their eggs. Trout can be seen chasing female egg-layers. Aggressive, splashy rises result.

Around 8:30 p.m. the temperature cools, egg-laying ceases and the emergence begins. As trout begin to take emerging pupae their feeding rhythm and risforms change. Dorsal fins and tails break the water surface as the trout take pupae just below the surface. The rises are deliberate and unhurried.

Trout feed primarily on the pupae although I do not use one. The Iris, X, and X2 caddis patterns work better than a strict imitation of the pupae. These flies imitate an emerging caddis stuck in its shuck and are fished dry in sizes #14-#16.

Glossosoma montana is the smallest caddis species in this area that can be significant to anglers. These tiny caddis are size #20-#22 with black bodies and wings. The can be important on the Henry’s Fork from June through August, on the Madison below Earthquake Lake from late June into early August and on the Firehole in June through September.

Even though they are a sporadic emerger they have a way of showing up unexpectedly in huge numbers when they do decide to hatch. It is then that the trout feed greedily on them to the exclusion of other, larger insects. This can be the case during reliable Hydropsyche emergences that often occur at the same time. When the Glossosoma do emerge heavily, and the trout take them and not the larger caddis it can be very frustrating if you aren’t prepared.

Have a #20-#22 X Caddis in your box at all times. This summer I experienced several times when large rainbows fed only on this tiny black caddis even though there were plenty of larger caddis species on the water at the same time.

Oecetis caddis, or commonly Longhorn Sedge, comes off area rivers like the Firehole, Henry’s Fork, Gibbon, and Madison Rivers in June and July. On the Firehole it will emerge again in September and early October.

This caddis has a long antennae, hence the Longhorn name. It sports a slender wing profile, extremely short body relative to their wings and a bright green to golden yellow body, size #14-#16.

On the Firehole it is a “new” hatch having shown up in huge numbers over the past 3 seasons. We are unsure why this occurs but the fish wasted no time rising to its activity.

The importance of this caddis is most dramatic during egg-laying time which is late afternoon or early evening. And while emergences and egg-laying flights are often sporadic, the use of a spent Oecetis pattern is highly successful on our rivers.

Early this fall I drove to the Firehole near its junction with Nez Perce Creek. It was mid-afternoon and quite warm for late September. I knew I’d have some evening caddis fishing and since it was still very warm I thought I could take my time and rig up on stream and wait for things to cool down and the caddis to show around 6 p.m. I walked down to the river and saw every fish in the river sipping insects. I took out my seine and scooped up several female Oecetis caddis, spent after egg-laying and being taken in a mayfly spinner-like rise. I did what the river told me to do and knotted on a spent-crippled Oecetis #15 (Tiemco hook), and had a banner afternoon.

Lepidostoma caddis is widespread in the Yellowstone area. The species L. pluviale is one of several species that is important for anglers.  It can be found bringing trout to the surface on the Henry’s Fork from mid-June to mid-July. On the Yellowstone and Madison Rivers along with Slough Creek it is an important insect to trout and fly fishers from mid-July to the end of August.

This caddisfly is a #16-#18 in size with an olive body and brownish-gray wing.

Fishing opportunities are both during emergences and egg-laying in the evening hours. The freshly emerged adults will ride the current for several feet and the trout love them. Lepidostoma emergences can be heavy and prompt lots of trout to feed. It is important to single out a fish and work it rather than flock shoot. This increases your chance that the fly will float over a fish when he is ready to feed. You must be ready to cast several times if the emergence is heavy.

This is one hatch where a pupal pattern works best, but an adult fly, which is much easier to fish, will catch plenty of trout too. Have a #16-#18 olive Antron Caddis Pupa. Adult patterns like #16-#18 Elk Hair, X, and X2 Caddis fish best when the emergence isn’t too heavy; in these cases the fish don’t get locked on the pupae so tightly. Always fish your patterns dead-drift.

Rhyacophila caddis are important on area rivers like the Madison, Yellowstone, Gallatin, and Firehole. The two most important species of Rhyacophia are R. bifila and R. coloradensis. R. bifila can be found hatching in July and August while R. coloradensis can be expected in September and October. Their larvae are an intense green, size #14-#16 and are found in turbulent pocket-water.

The adults have lovely mottled wings of gray and black with rich olive bodies, size #14-#16.

I have never witnessed a huge emergence of this caddis although adults can be found in exceptional quantities along rivers in summer and fall. And, because these caddis are on the water for four months I think trout recognize them and will often take an imitation of the adult any time they are around. I have had wonderful success searching the water when no rises occur with a #14-#16 olive X and X2 Caddis. I fish these flies in all likely pockets and in the heaviest flows as this is where the larvae live and the adults emerge.

Of all the caddis we have discussed, this is the only genus whose larvae overshadows the adults in importance to fishermen. This anomaly is due mostly in part to the primitive nature of this caddis. The ability to build a protective case is a measure of evolutionary advancement in caddis, and this feature is absent in this genus. Rhyacophila larvae range freely over the rivers’ bottom, without protective stick or stone cases most of their relatives possess. Since the larvae are present in mature form from June through October and since these intense green larvae occur in the natural drift of a stream, trout have plenty of chances to prey on them. There is no doubt that fish recognize this bright green and that imitations of Rhyacophila larvae are among the best choice of fly to fish in rivers where they are found when no surface feeding is occurring.

A larvae pattern is an important searching fly to try during those times when no insect emergences are taking place. The fly should be fished in the heaviest pocket water; upstream, dead-drift. This is the easiest way to maintain a drag-free drift, it is less likely to spook fish, and it allows a strike to be quickly detected.

For a larvae pattern have a #14-#16 bright green antron dubbing for the abdomen with a turn of two of starling for the legs and a black dubbed head. The dubbing should be wound over a foundation of lead wire.

I hope to see you fishing caddisfly activity next season in Yellowstone country.