May 01, 2022
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This article originally appeared in the September1987 issue of Fly Fisherman magazine. Click here for a PDF of the print version of "Mother's Day Hatch."
The "Mother’s Day hatch" is a phenomenal caddisfly emergence that takes place on the Yellowstone and Madison rivers around the second or third week in May. With luck, on a good year the hatch remains in full swing during Mother's Day weekend, hence the name. This hatch is Montana's version of the famed mayfly hatches that occur in the Michigan area each year. However, unlike in Michigan where road graders sometimes must clear bridges of mayfly bodies, Montana only has to ensure that the roads are in good condition for the diehard locals that hit the rivers.
The great numbers of caddisflies that emerge in such a short time makes this hatch spectacular. Within three or four days literally millions of caddis take to the air. To aquatic entomologists such an occurrence is known as the "predator swamp tactic." The theory is that if enough insects emerge at exactly the same time, their predators, the fish, will feed until they are satisfied and thus be unable to make a sizable impact on the emerging population. In other words, if you as a caddisfly emerge with your family, cousins, and all your friends, a few of you are going to be eaten, but most will survive to reproduce.
How do the fish react to this? Imagine yourself waking up hungry one morning and finding someone with a truck load of delicious free food at your door and telling you that you can have as much as you can eat. No one would pass up the chance to gorge himself. Well, the trout on the Yellowstone and Madison cannot contain themselves either. During the first days preceding the hatch the fishing is fantastic. The trout have keyed in on the large number of active caddis that emerge slightly out of sync with the mass of insects. Then on the days when the caddis are as thick as snowflakes during a Montana winter whiteout, the trout still try to get as many free meals as possible. The largest trout gladly forsake their holes to feed on the floating caddis mats clogging the eddy lines. In back-eddies such as the one shown with guide Robin Cunningham (holding a handful of caddis flies) trout heads the size of small footballs break the surface to gulp mouthfuls of wriggling bodies.
The time of day that a fisherman should get on the water during the Mother's Day Hatch depends on the length of float he wants. This does not mean that a wading fisherman cannot capitalize on the hatch, but to catch the greatest number of fish floating the river is best.
Early in the day, as the boat starts down the river, you notice a few caddis actively flying near overhanging trees and bushes. Nothing seems different from any other Montana fishing day. As the day warms, however, more and more caddis fly in the ever-present breeze, until suddenly entire clouds of brown caddis appear and the fish turn on. In minutes fishermen in both ends of the boat begin landing trout of varying sizes, or at least turning fish. Because the fishing is so spectacular, no one notices the ever-growing hordes of caddis in the air. No one notices, that is, until the fisherman in the "hot seat" turns to brag about the size of the whale he has hooked and he can only cough because he has inhaled a mouthful of wings. Then, the hatch really begins!
The hordes of emerging caddis belong to the family Brachycentridae. This family consists of approximately 31 species. Most individual adults are 5mm to 12mm long with grayish-brown bodies. As larva they are generally clingers and climbers and construct tube cases that may be square in cross section. They favor fast-flowing water, and their diet consists of leaves and detritus. The adult female caddis have a green teardrop mass of eggs that hangs from their abdomens, making them easily distinguished from the males. Although some female caddis may live as long as a month before ovipositing, the female members of this hatch apparently waste no time in laying their eggs and then expiring on the water.
As the day progresses, anglers become overtaken by the optical illusion of moving faster than the boat can go. With so many caddis in the air, seemingly flying in the same direction, a fisherman experiences the same sensation as driving through a raging snow storm in which the movement of the car and the flakes gives the occupants the feeling that the speedometer is "pinned."
The river soon appears as if it is in the throes of a muddy spring runoff as hundreds of thousands of caddis drift in the current. Caddis bodies become so thick on the water that in many of the back-eddies a person may feel that he could throw his hat onto the surface and not get it wet. Caddis crawl all over the boat, your gear, your face and glasses, and even down the length of your rod as if to help entice the fish. And all the while, fish break the surface just about everywhere.
On the days before and after the main emergence, a #14 or #16 Elk hair Caddis works best. Because of the vast numbers of bodies on the water when the caddis are peaking, however, a fisherman must continually tie on a slightly larger fly as the day progresses. By the end of the day, the fish have become so full that they rarely come up to hit anything smaller than a #10 Elk- or Deer-hair Caddis. On the days following peak emergence, Royal Trudes and Western Coachmans also work well. The advantage of these last two patterns is that they may be fished dry or as swimming flies–both methods produce extremely large fish. Working colorful streamers close to the surface is another productive way to fish this hatch.
For some anglers the Mother's Day hatch is extremely frustrating. They simply become overwhelmed by the number of insects on the water, but they cannot see their floating fly or catch fish. At such times, the wisest move that one can make is to sit down, relax and marvel at the phenomenon before him. This is a time for contemplation, a time for introspection, and a time for wondering about the complexity of nature and its creatures. But most of all, this is a time for catching your breath and for calming down before returning to the water to catch the big fish that continue to rise all around.
A word of caution for those who have allergies or asthma. The caddisfly has a hairy wing that separates it from its close relative the moth, which has a scaly wing. When such a large number of caddis emerge, lots of these tiny hairs break off, irritating allergy sufferers. Just such an occurrence took place during the Montreal Olympic Games. A caddis hatch sent a great many people scurrying to local hospitals only to discover they had yet another allergy.
As the day comes to a close, the fishermen are tired, the fish are full, but the caddis still seem to increase in number. By now, everyone can empathize with the sobering alcoholics who experience the feeling of bugs crawling all over their bodies. A glance around the boat shows dead caddisflies everywhere. Later, while undressing for the day, sobering fishermen notice dead caddis bodies in every pocket of their shirt and pants. For days, even weeks, later, caddis bodies turn up in anything that was in the boat during those few unforgettable days.
So why is it that only the locals take advantage of this spectacular occurrence? The sight of the first early caddisflies usually signifies that runoff is close at hand. Some years the peak caddis emergence occurs during high water, making it impossible to fish successfully. Still, in other years such as 1986, the caddis emerged about a full week before runoff. Also, in 1986 the weather was kind enough to cool off for two weeks after runoff began, clearing the rivers for an additional week of fantastic fly fishing.
The uncertainty of the weather, caddis emergence, and runoff make this hatch an iffy proposition for out-ofstate fishermen. For those that do make it, the ambiguity of the circumstances is completely erased by the awesome spectacle and by the tremendous fishing that takes place.
Being on the Yellowstone or Madison rivers and seeing a snowfall of caddisflies is truly a humbling experience. Catching the big trout during this time only adds to the pleasure of the trip. For information about spring prospects, outfitters such as Avon Outfitters, or local Bozeman fly shops such High Country Angler or The River's Edge, can answer your questions or book your trips. An early arrival next year could make for some great fishing in the Bozeman area, but arrive too late and you may only find that spring runoff has made all the rivers unfishable.
Buddy Drake, an aquatic habitat consultant, lives in Bozeman, Mont.