Wood River Hex Hatch

Primarily a caddis river, the Wood hosts good Black Quill, Hendrickson, Gray Fox, Mahogany Dun, Blue Wing Olive and other mayfly hatches. Beginning in mid-June every year, it plays host to one of the most beautiful and exciting flyfishing experiences to witness and fish: the “hex hatch.” Like the mayflies mentioned above, Hexagenia limbata is a member of the Ephemeridae family and is one of the largest mayflies in North America. It’s widely distributed throughout the waters of the northeast and mid-west. During its emergence, or hatch, from Rhode Island’s Wood River the trout become voracious feeders on the rising nymph, on the surface “the dun” and on the fallen “spinners”. Because this hatch is so prolific and sudden, and the fly is so large, trout are very excited by the event. It is the quintessence of fly-fishing: a predictable hatch with selective actively feeding trout.

Like all aquatic “hatches” this event is not a hatch of newborns. It is an emergence, from under the water to the surface, of sexually mature aquatic creatures. After living under the water as nymphs, the mayflies that we affectionately call “the hex” achieve procreative maturity and come to the top. There, they dry their wings and fly off for the sole purpose of mating. The female hex mayflies return to the water a couple of days later and deposit their fertilized eggs. The eggs sink to the bottom to hatch into nymphs to start the next generation of these wondrous creatures.

The adult hex can have an abdomen that will range in length of a good inch and a half long. It is mostly yellow with reddish brown markings on the abdomen, wings that are a veined translucent gray, and two long tails. The adult makes its appearance only at sunset; the hatch’s peak is always after dark. Fishing the “hex hatch” is an eerily captivating and very exciting experience! Below will detail the stages of the hatch and what fly patterns are most effective.

How to Fish the Hex Hatch: Know the Stages

The Nymph and the Emerger

The hex nymph is a burrower. After numerous molts, when it has achieved some size and strength, it can be found as deep as a foot into the silt or mud. Its habitat: the rich soft bottom in slow or still silty areas of streams and lakes. The nymph will tunnel upward to feed and to molt, usually on a cloudy dark day or in the evening. Since it has been revealed that trout eat the hex nymph throughout the year, it should be a sound strategy to try a hex nymph pattern, at or near the bottom, any time you are in a silty part of a hex rich river. Fish might take it from memory at any time but more likely when it is overcast or dark when the nymphs are active outside their burrows.

The nymph, itself, has a long slender body with three hairy tails and its body is lined with gills at the sides. The head has a pair of tusks plus a pair of feelers (neither are important in imitations). The thorax has three pairs of powerful legs and the color is, roughly, a pale yellow-brown, sometimes olive brown. The gills are darker and the legs about the same shade as the body.

During the emergence, the fly pattern and the technique for fishing the nymph will be different. Nymphs, now with bulging wing cases, detect the coming evening. The ones that are ready, will burrow up from the silt for the last time. The nymph is a strong swimmer and as it emerges, it undulates, porpoise-like, upward. This undulating movement has inspired segmented or ‘flex bodied’ fly patterns to help mimic this natural motion. When the sun sets and the first whippoorwills cry out, the ‘popping’ of emergers on the water’s surface will follow. They will free their wings to dry and finally become airborne.

Prior to the first observed emergence, try fishing the newly active nymphs along the bottom. Then, in order to attract fish that are intercepting emergers, use a weighted imitation. Let it sink to the bottom and lift it with pulsating pulls to imitate the insect’s propulsion upward. Trout are also apt to notice the surfaced emerger. These can struggle for as long as ten minutes in or on the surface film before the wings burst completely free of their case. Experienced anglers of the hex hatch have sworn by the emerger pattern fished in or on the surface film for the hatch’s entire duration. A floating emerger pattern, fished dead drift with very short occasional twitches will imitate what the trout will be seeing.

The Dun and The Spinner

The fully winged adult (dun) is as nutritious as the nymph and the emerger. Females do not land on the water to deposit eggs for two to three days after emergence. In other words, any ovipositing (egg-laying) females or spent adults are from an emergence two to three days earlier. The ovipositing process puts the female on the water, shuddering as she expels the eggs which fall to the bottom to hatch and carry on the insect’s life cycle.

Spinner water is not necessarily emerger water. Insects would disappear from our streams, traveling downstream and out, if the instinct did not drive the other insects upstream. Spinners therefore may appear in riffles above the emerger waters. Drifting spinners can be found over a long stretch of water as they drift following the ovipositing (as dying females and males). Spinner falls may last till past midnight. On cloudy days, spinner activity may begin before dusk; therefore, fishing the spinner is as good a strategy as any. In fact, it’s my favorite for fishing this hatch! Sometimes, I stick with fishing the spinner all evening long.

For my Dun imitation (a white or yellow-bodied Wulff pattern) I like to use a size #10 dry fly hook, such as a Mustad Dry Fly Hook, (R50NP-BR) size #10, 1x long. Most of the time I use light yellow rabbit fur dubbing for the body, and white calf tail for the tail and the divided wings. The hackle is from either a brown furnace or light dun neck, tied sparsely. This is important because I have to be confident that the imitation will float during those hard-to-see times. A large fly such as this will float longer if it has been tied sparsely. Once the hatch starts, at around 9:00pm, I will likely fish the spinner imitation right through the hatch! On some occasions I will fish my emerger imitation, especially when I note that the fish are not taking my spinner. Remember: cast carefully to your predetermined spots and use a short strong leader tapered down to 1 or 2x (8-9Ib).

On The Water

The Hex Hatch on the Wood River normally begins mid-June. It generally starts June 16th or 17th and it can last for up to eight weeks if we have a hot humid summer. If the weather is cooler and dryer, then we can expect it to last for around six to seven weeks. The peak time for this hatch is from the 4th of July to the end of July.

Tips for a successful Hex Hatch fishing experience:

• Prepare before the sun goes down. The Hex Hatch is a night-time event so pack a flashlight and headlamp. The light I use while fishing and changing flies will always have a red filter lens. This will help you keep your night vision.
• Arrive early to pick your spot; it is a popular event. Study your environment and practice casting while it is still light. I will start fishing this hatch at 7:00pm on “hex nights”. Though these mayflies will not appear until about 8:55pm, the first week or so during which the fish have been seeing this emergence can prime them to become instinctively aggressive even earlier in the evening.
• The Wood River is wadable. While underneath most of this water it is muddy and silty, ideal Hex habitat, you can comfortably navigate the substrate. The river has a slow to moderate water flow, on long placid runs and the bottom includes a mix of harder stone and gravel with soft edges. It is recommended to bring along your wading stick.
• Fishing at night is easier with a short leader. Six feet of 1x or 2x monofilament, not tapered, is a good leader length. Artificial flies are not wind resistant when false casting, so a 1x or 2x will keep your leader from turning into a slinky-like mess!
• The Wood River is not deep, so even if you are fishing a nymph from the bottom you can use a floating line with a weighted nymph.
• Don’t miss an opportunity to examine this extraordinary mayfly. It can be stopped on your arm with a light. Take a chance to admire it.
• Warm humid nights without wind are most likely to encourage the hatch.
• Observation is the key to success