Al Campbell, Field Editor

April 28th, 2003

Where To Fish A Hatch
By Al Campbell

It's early morning and you see some mayflies floating down the stream. Where will your chances for success be best? It's mid morning and caddisflies are hopping off the water in clouds. What is the best approach to this situation? It's late afternoon and caddisflies are returning to the water to lay their eggs. What can you do to maximize your chances for success?

Those are common questions I get asked in one form or another all summer long. The new guy is using the right fly, he's on the right stream, he's wearing the right clothes, but he can't buy a strike. The guy a few hundred feet upstream is catching one fish after another while this poor soul is doomed to watch the show and go fish-less for his efforts. Why does that happen?

I think we can find an answer in the habits of insects and the fish that eat them. Certain insects act in certain ways, and the fish react to those insects in predictable ways. If you understand the insects and how fish react to them, you can profit from that understanding with more fish on the end of your line. Let's look at the four major groups of aquatic insects, how they hatch, how they lay their eggs, and how the fish react to them; and then see if it helps us understand better how to use that information to our advantage.


Mayflies, like all aquatic insects, have a bunch of sub-families and each family has a few differences in how they act. However, there are a few generalizations that can be helpful in our quest for fish. When mayfly nymphs reach the level of maturity to move to the surface to morph into their first stage of adulthood, many of those nymphs make that move by swimming to the surface. This movement puts the nymphs in harm's way as they travel through the dining area of the fish. Fortunately, the nymphs have a trick or two to minimize the threat.

Mayflies in moving water tend to migrate to faster and shallower water to make their move to the surface. This results in a shorter trip and less surface tension they have to deal with. The unlucky nymphs who happen to make the trip in deeper water with a calm surface (lakes and deep pools in moving water) find the trip more perilous and the surface tension much harder to break. As a result, the sub-species that hatch in slower water are usually better swimmers. They also tend to have more stillborn casualties (flies that didn't succeed in busting the surface tension) than mayflies who emerge in fast water.

Fish react to these differences in different ways. When a hatch is getting ready to start, fish in moving water start seeing nymphs drifting in the water after they were dislodged while moving into fast and shallow water to prepare for emergence. The fish move up into that thin water to feed on the nymphs that are drifting near the bottom. As the hatch starts, the focus of the fish shifts to looking for movement toward the surface. Then, as more adults emerge and ride the surface of the water, fish start looking for adults on the surface to feed on. In most cases, the feeding habits overlap as the hatch progresses.

In calm water, mayfly nymphs are usually swimming sub-species designed to travel the longer distances from the bottom of the water to the top. Fish first key in on a hatch by noticing the swimming ascent to the surface being made by growing numbers of nymphs. In this case, motion is a key factor in fish feeding behavior. Movement upward and jerky movements just under the surface signal to the fish that insects are ascending to the surface and trying to break through the surface. As more insects are successful in this migration, fish eventually turn more attention to the mayflies riding the surface, but for the most part, the fish are more attuned to the jerky movements just under the surface.

When a hatch is just starting in moving water, a dead-drifted beadhead or weighted nymph of the right size and color can be your best bet if you concentrate your fishing on the faster and shallow water of the riffles and rapids. As the hatch progresses, an upward lift applied to the nymph can often result in more strikes. When significant numbers of adults can be seen on the surface, match the insect with a dry fly and concentrate your efforts on the areas where the riffles lead into pools. The majority of the fish will be in these areas feeding on insects that are acting this way.

After mayflies mate, they return to the water upstream from where they emerged and lay their eggs in pools of calm water. The eggs drift to the bottom to restart the cycle and the adults die on the water's surface. Fish will be feeding near the bottoms of those pools or anywhere the water swirls to concentrate the dead adult mayflies. In lakes, fish will swim under the surface and pick off dead mayflies at random but somewhat predictable intervals. In both cases, flies should be presented by dead-drifting them on the surface.


Caddisflies share some habits with mayflies, but they are also very different. Caddisflies prefer to emerge in shallow, moving water like mayflies, but they do so much faster than mayflies. Their pupae are also better swimmers than mayfly nymphs. Unlike mayflies who often drift for up to an hour while their wings dry, caddisflies are often airborne within seconds of their emergence on the water's surface. Before the hatch occurs, caddisfly larvae pupate, so you don't see a concentration of caddisfly larvae near the bottom just before the hatch.

Fish key in on the hatch by looking for rising and swimming pupae as the hatch starts. Since the adults spend so little time on the surface before they fly away, adult patterns are less important than wet flies that imitate the emerging pupae. Fish in lakes look for the rising pupae and the jerky motion of pupae just under the surface trying to break through the surface tension to emerge as adults.

Most adult caddisflies lay their eggs by flying upstream while skimming the water's surface and dipping their tail to deposit their eggs, or landing briefly to deposit some eggs then flying upstream to another location to repeat the land and go process again many times. Egg laying is often done in the riffles just above pools or at the head of pools. After the eggs are laid, the adults often fly off to die on land instead of on the water like adult mayflies.

The best approach to fishing caddis hatches is to concentrate on riffles with a wet fly that imitates a rising caddis pupa, fishing a surface emerger like a sparkle pupa with a slight twitch, or fishing a sparsely tied adult with a jerky of fluttering twitch. To imitate an egg laying adult, skitter an bushy fly like and elk hair caddis on the surface with an upstream movement. Especially effective is a stop and go skitter that allows the dry fly to pause for a fraction of a second before it moves upstream again. Motion of your fly is important in both the emergence and egg laying stages of the life cycle.


Midges are very similar to caddisflies in many ways. However, they seem to prefer calmer water to emerge in, spend more time working through the surface tension, and often return to the water to lay their eggs in mating clusters. Larvae imitations usually fish best in the heads of pools and along seams in slow moving water. Emerger patterns usually fish best in the calm water near the head of a pool, fished with a short twitch to imitate insects trying to break through the surface tension. Cluster type flies like the Griffith's gnat are effective egg laying adult imitations and fish best on a dead-drift with random short twitches. Lake fishing is similar to caddisfly fishing except any movement should be slower and in much shorter increments.


Stonefly nymphs usually crawl out of the water to emerge as adults on rocks or weeds near the edge of the stream. As a result, they are usually available to the fish only as dislodged nymphs or egg laying adults.

As the hatch nears, nymphs move along the bottom of the stream to the water's edge where they crawl out. Many of them become dislodged and are available to the fish near the bottom of the stream, especially near the edges of the stream. Imitations fish best when dead-drifted near the bottom and near the stream's edge. Adults usually lay their eggs by dipping their tails into the water as they zigzag upstream in flight. Bushy patterns like the stimulator that are skittered in a zigzag motion upstream are often most effective. Eggs are usually laid in the bottoms of riffles or the tops of pools. Adults usually die on land, so dead-drifted adult patterns aren't usually as effective.

We didn't cover dragonflies and damselflies, but those are best left to another article. At best, this is a simplified version of how the insects act and how the fish react to them. However, if you pay attention to the stages of the hatch and fish accordingly, your catch rates should improve a lot. ~ AC

Previous Al Campell Columns

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