By Spencer Durrant
The first epic dry fly hatch I remember sitting through was a caddis hatch on a small freestone stream in the Rockies. It was early evening, sometime in summer, and the bugs were coming off in thick clouds. I couldn’t catch a thing. I was failing miserably at matching the hatch.
For the first few years of my fly fishing life, that story replayed itself during many hatches on my local rivers and streams. I couldn’t ever figure out a dry fly hatch the way it was described in fishing books and stories – where every cast results in a hookup, in the visual joy of watching trout rise to a fake fly.
If you know a few key tactics, though, dry fly hatches can quickly go from mystical to fairly easy to decode.
Mayflies, Caddis or Midges?
The first question to answer in order to be successful in a dry fly hatch is what’s hatching. Stoneflies are easy to identify, which is why I didn’t include them here. That, and you’re far more likely to get frustrated during a mayfly hatch than a stonefly hatch.
Mayflies, midges, and caddis make up a huge portion of any trout’s diet. Quickly identifying each of these bugs is a key to being successful during a dry fly hatch.
Caddis are medium-sized flies that have two big wings and long, slender bodies. Their bodies aren’t as tapered as that of a mayfly.
Caddis are usually light to dark brown. When they fly, they seem to flutter and swerve. They’re certainly not the elegant flyers that mayflies are.
Best Fly to Imitate a Caddis: Elk Hair Caddis, size 14-16
Mayflies can be very large, but they’re often smaller. They have long, slender bodies that are tapered, with a very distinct tail. The wings are large and stick straight up, instead of laying alongside the body like a caddis.
There are a ton of different mayflies, but some of the most common that anglers focus on are blue-winged olives, pale morning duns, green and brown Drakes, March browns, and Hendricksons.
Best Fly to Imitate a Mayfly: Adams, PMD, BWO size 12-18
Midges are the smallest flies, and often the most frustrating. They hatch year-round, and usually hatch alongside other bugs. Fish are often eating midges even in the middle of a mayfly hatch, because the midges are easier to reach.
Midges are a main food source in winter, early spring, and late fall. Fish eat them year-round as nymphs as well.
Best Fly to Imitate a Midge: Griffiths Gnat, Renegade, TS Midge, size 18-22
Identifying bugs while on the water might seem like a tough job, but it’s pretty easy once you know what to look for. The next time you’re out fishing, take a few minutes to just sit and watch the river. You’ll see bugs coming off, so quiz yourself on what they are. You’ll be surprised at how quickly and easily you can identify the different types of bugs hatching.
Watch the Rise
Once you’ve identified what bugs are hatching, the next step is to watch how the fish are rising. The way a fish rises creates what we call a rise form. Rise forms tell you a ton about what fish are eating if you know what to look for.
Head Breaks the Surface
If you’re watching fish rise to dry flies and you can see a fish’s head breaking through the surface of the water, those fish are most likely eating the adult version of a dry fly – often called a dun.
Flies That Imitate Duns: Adams, Parachute Adams, Elk Hair Caddis, PMD, BWO, Griffiths Gnat
Dorsal and Tail Fin Break the Surface
If you see fish rise, but only see their dorsal and tail fins break the surface of the water, that means the fish is eating bugs that are stuck in the surface film. Most often, these bugs are either emergers not quite fully turned into a dun, or they’re crippled (bugs that are injured and can’t escape the water).
Flies That Imitate Emergers: Last Chance Cripple, Comparadun, RS2
Nothing Breaks the Surface
If you don’t see any part of a fish poke out above the water, but you clearly see a dimple on the river’s surface, then that means one of two things. Either the fish rising is very small, or the fish is sitting just below the surface and sucking in flies without coming all the way up. In either case, a dun or emerger is a great option.
Matching the Hatch
Once you’ve identified which type of fly is hatching, and what the fish are eating, it’s time to start matching the hatch.
Let’s say you’re in the middle of a blue-winged olive hatch. You arrive at the river to clearly see mayflies buzzing, and the fish are eating emergers. You know this because you only see a fish’s dorsal and tail fins breaking the surface when they come up to eat.
The next step to successfully matching the hatch is to take a closer look at the flies. You want to match what the fish are eating based off the following factors:
I listed those factors in order of importance. Being successful during a dry fly hatch depends far more on fishing flies that are the right size and shape than it does the color of the fly you choose. On all but the most pressured of tailwaters, fly color doesn’t usually matter much.
That’s why it’s so important to learn how to identify the bugs that are hatching. If we go back to our hypothetical blue-winged olive hatch, let’s say I arrive at the river and see fish eating emergers. I look at flies on the water’s surface, as well as some of the duns buzzing through the air. I see they’re small – size 18 or 20 – and fairly dark.
I’ll first look for a dry fly in size 18 or 20 that’s roughly the right shape as a mayfly. Great examples of flies like this include any of the Adamses. An Adams has the long, slender, tapered body of a mayfly, and when tied in Adams gray, is usually a great match for early and late-season blue-winged olive hatches.
Once I’ve found a fly that’s roughly the same size and shape as what I’m seeing fish eat, then I’ll tie it on. If the fish refuse it, I usually change it for a size smaller, or pick a color that more closely matches the bugs already on the water.
Unmatching the Hatch
In some cases, matching the hatch exactly doesn’t really increase your odds of catching fish. For example, I fish the Green River in Utah more often than just about any other river. It’s big water, with absolutely legendary blue-winged olive hatches. Most of the bugs that hatch are small, but with so many on the water, the chances that yours is eaten are slim.
Unmatching the hatch, then, becomes a valuable tool. When fishing the Green, I try to match the shape of the bugs hatching, but not the size. Going up to a size 14 blue-winged olive, for example, puts more fish in my net than trying to use an exact replica of the size 18-22 bugs on the water.
Unmatching the hatch works on pressured waters, or on waters with prolific hatches because it offers fish a higher-value meal for the same amount of work. Fish are instinctual. They want to expend the least energy possible in exchange for the maximum amount of food. If they’re already rising to hatching bugs, but they can eat a more nutrient-rich size 14 blue-winged olive instead of a size 18, which do you think they’ll pick?
There are other instances where unmatching the hatch makes sense, but those are often situation and water-specific. I’d only recommend going this route when you’re faced with a prolific hatch of thousands and thousands of bugs.
Matching the hatch isn’t nearly as tough a job as it sounds. It really just requires a bit of attention on your part, and a willingness to learn more about bugs. The more time you spend watching a river and fish eating flies, the easier time you’ll have of matching your next great dry fly hatch.