The Hex Hatch – A Magical Time of Year
by Dean Growdon
Many people aren’t familiar with what anglers mean by the “Hex” or the “Hex hatch.” For fly anglers, though, it’s a special season that feels almost like a holiday – a month long celebration of a remarkable natural event.
Right now, Hexagenia limbata, a giant yellow to tan mayfly, is hatching on some of our local waters. During the peak of the hatch each evening, fish, birds, and bats erupt into a feeding frenzy. Anglers travel from all over to experience and fish this event, many of them focused on the big trout and bass that key in on the Hex.
But the Hex hatch isn’t just for fly anglers. In this week’s article, I’ll take a closer look at the Hex hatch and share strategies for fishing it.
What It Is
Hexagenia limbata (often simply called “Hex”) is a large burrowing mayfly that hatches on Lake Almanor, Butt Valley Reservoir, the Fall River, and many other lakes and rivers across North America. These insects thrive in slow sections of rivers and in lakes with soft, silty, or muddy bottoms. As nymphs, they burrow into the substrate and remain there for 1–3 years before hatching.
When water temperatures climb past about 60 degrees, the nymphs begin leaving their burrows and become active along the bottom. Emergence typically occurs from dusk into the evening, with the strongest activity usually when water temperatures range from about 63 to 68 degrees. In our area, the hatch generally begins in early June and continues into early July, though the peak varies with temperature and location. For example, Butt Valley Reservoir (or Butt Lake, as locals call it) warms more quickly than Lake Almanor, so the Hex hatch there usually peaks a bit earlier.
As the Hex emerge, they shed their shuck (the nymphal exoskeleton) and transition into the dun stage. The duns are bright yellow to tan and ride the surface for a short time before taking flight. While they’re on the water, they are prime targets for fish, birds, and bats. Once airborne, the duns head to nearby trees or shoreline vegetation, where they molt again into the “spinner” phase. Males and females mate in midair, and the females then drop their eggs onto the water, where they sink to the bottom and develop into new nymphs. The adult spinners soon die, often falling back onto the surface and providing one last burst of food for hungry fish.
Fly Fishing the Hex Hatch
These mayflies provide an important food source for both wildlife and fish. This is one of the few times of year when you can consistently target larger fish on these waters, especially with a dry fly. Anglers use a wide range of techniques to chase these big fish; below are a couple of the most effective.
Nymphing
Although the surface action at dusk is spectacular, it’s important to remember that fish feed on far more nymphs than duns (dry flies) and eat them throughout the day. To fish nymphs effectively, you need to get close to the bottom, often in 18–25 feet of water.
Two common ways to reach that depth are:
- A sinking line fished very slowly to keep the flies just off the bottom.
- A sliding indicator (bobber) rig that suspends the flies at the desired depth.
The sinking line approach works best from a float tube, personal pontoon, or other small craft that lets you kick along slowly. The sliding bobber setup tends to work well from a boat or from those same small craft.
For the sliding bobber rig, I like to run a 25 foot section of 15 lb test monofilament off my fly line. I place two bobber stops on the mono with a sliding bobber between them. On the terminal end of the mono, I tie on a micro swivel, then add a 3–5 foot section of 8 lb test fluorocarbon. I tie my first nymph pattern to this—usually some type of balanced nymph or leech pattern—then add a 3–5 foot section of 6 lb test fluorocarbon down to the bottom fly, typically a beaded Hex nymph. If the line doesn’t slide easily through the bobber, I’ll add a split shot to help it along. Adjust the bobber stops so your bottom fly rides just off the bottom.
Dry Flies
Dry flies haven’t been as consistently effective over the past few years, likely due to higher water conditions, but they can still produce fish. I usually switch from nymphing to dries as soon as I see fish starting to surface, which is often just before the peak of the evening hatch. This timing lets you target fish before your fly has to compete with thousands of naturals.
I prefer to fish dries from a boat with a trolling motor, casting toward actively rising fish. Once the fly lands, I give it a short strip or twitch every few seconds to impart a bit of life.
Flies and Rods
There are a variety of Hex nymph, emerger, and dry fly patterns available. I recommend seeking out a local fly shop that sells Hex patterns; you’ll often get a current fishing report and some friendly, up to date advice along with your flies.
As far as rods go, I use 6 weight rods for both nymphing and dry fly fishing during the Hex hatch. It is not uncommon to hook a smallmouth in the 4–5-lb range or a brown trout over 8 lb. You need a rod with enough backbone to fight these fish and a reel with a solid drag system to match.
Catch and Release
There are a few important considerations if you plan to release fish and want to maximize their chances of survival. When nymphing deep, you’re bringing fish up from cooler, more oxygenated water into warmer surface layers. It’s important to land and release them as quickly as possible and to keep them in the water as much as you can.
I recommend using a 6 or 7 weight rod with enough power to shorten the fight and reduce stress on the fish. When releasing a fish, hold it upright and underwater until it’s able to swim away on its own.
Depth is another factor. I avoid nymphing deeper than about 25 feet, because fish brought up from greater depths are much less likely to survive the pressure change and temperature difference.
Traditional Fishing Techniques
You don’t need a fly rod to enjoy the Hex hatch. With a traditional spinning rod, you can use a sliding bobber nymphing setup very similar to the one described above. Another effective option is a drop shot rig, with a weight at the bottom and one or two nymphs tied on short tags off the main line. Fishing just off the bottom with natural baits such as mealworms or crickets can also be very productive.
If you plan to release your catch, I encourage you to pinch down the barbs on your hooks. Barbless or de barbed hooks make for quicker, cleaner releases and are easier on the fish.
A Season Worth Seeing
The magic time of year known as the Hex hatch is upon us. Get out and experience this natural wonder for yourself. Whether you’re out there fishing or simply watching from shore, it’s an extraordinary event to witness and one of the true highlights of our fishing year.
