The “Hex” mayfly is the second largest mayfly in North America (the largest is Litobrancha recurvata) and is know to reach as much as 1.5 inches in size. They live in muddy lake and river bottoms and hatch right before dark. Female Duns have lighter yellow bodies and smaller eyes than males and are typically several millimeters longer than males. Female Duns can also be twice the mass of males. They can vary in color from yellow to white to shades of brown. Hexagenia mayflies are found widespread across the United States especially around the Great Lakes and is the most widespread burrowing mayfly species in North America. When the Hex’s hatch, there is a small window of mayhem from sunset to darkness that the biggest fish in the watershed key in on for an easy meal. There is nothing quiet as exhilarating as watching large trout eating large mayflies.
Lake Almanor in California has a famous Hex hatch in July on the west shore. Often it attracts so many anglers that the sea of rafts and tubes are casting distance apart in heavy traffic. The bugs hatch in the muddy lake bottom in 20-50 feet of water starting just before dark.
The Fall River also has a hex hatch that peaks in July. The Hex game on the Fall river starts just before dark and ends in pitch black. Having a headlamp and a spotlight is essential to tie knots at night and to navigate the river in pitch black.
The Hex Hatch at Henderson Springs may be the easiest and best place to experience these giant mayflies. Located 40 miles from the Fall River and 100 miles from Lake Almanor, Henderson Springs Ranch is a private fishing lodge with 5 lakes to choose from. Mark Henderson discovered the Hex Mayflies in one of his ponds many years ago and transplanted the mud from that lake to the other four lakes. Now all the lakes have an evening Hex hatch that happens in late May to the end of July.
The nice thing about fishing the hex hatch at Henderson Springs is that you can fish if from the shoreline or a float tube unlike at Lake Almanor and the Fall River. The lodge has very comfortable accommodations and I especially like cooking my own meals so I can stay out later and eat after the late hatch. I concentrated my fishing on the mud flats on Long Lake from the shoreline. I could see the fish cruising the mud flats for active nymphs before the hatch started and in the shallow water, its easy to spot cruising waking fish. Also, the fish have a shallower angle of attack on the fly and are less selective. I caught half a dozen fish in 1-2 feet of water fishing dries, cripples and nymphs. The other three fishermen on the lake fished the deep side of the lake and were hooking many large fish on Duns. When the Duns hatch, they land or drift all over the lake and the big fish key in on them during the magic hour. Getting a 2 inch mayfly into a trout’s small mouth involves some force. The rises are often explosive and wild. Sometimes fish will chase an emerging nymph and leap for a Hex that is barely airborn. Unlike the leisurely afternoon rises for Calibaetis, trout that are hunting for Hex’s have to act fast before they loose their prey.
It might seem that fish would eat them with wild abandon feeding on the swimming nymphs, the emergers, the cripples and the huge duns, but not so. They still key in on size, siloette and in the early part of the hatch color. As it gets darker and it gets harder for the fish to see, but they do get braver and fishing usually peaks right before the hatch ends. I watched a fisherman work a large size 2 Female Dun over feeding fish that was repeatedly rejected and not in a subtle way. Fish would race to it on multiple occasions and turn away at the last moment. Other times I would get violent strikes just twitching a still fly after a couple minutes.
The conditions were far from ideal this weekend for a big Hex hatch. It rained alot and the temps dropped into the 40s. The water temps dropped from 61 to 58 from the cold rain and weather, but still the Hexs came off like clockwork from sunset to darkness lasting about 2 hours from 7-9. Both nights I caught half a dozen fish and lost and or missed a couple more. Its a short window of opportunity but lots of action across the entire lake. At dark, the fishing slowed down and the bats came out often picking up the fly from the water and dropping it . I think the fish actually loose out to the bats. I also think that the fish don’t see color as the light gets low and that sillohete is important. I fished a nymph on an intermediate line from 6-7 , a dry dun from 7-8 and a cripple from 8-9. All seemed to work well but I think the cripple was the most effective. The Male duns are smaller and its easier to hook a fish on a size 8 fly than and extended boy size 4 fly. I think a smaller fly presented to a cruising fish was the best tactic at Henderson this weekend. Next time I will have more 1 inch patterns. Bringing some scissors out can be handy to cut down some of the bigger flies and don’t forget a headlamp when you bust a few off on 4x. I used 3x tippets with no issues.
Catching lots of fish at Henderson on leeches on a full sinking line is a no brainer. It is tons of fun and non stop action but after awhile, there are other games to play that are very challenging. The morning calibaetis hatch and evening spinner fall is something you can always depend on at Henderson’s. When the wind dies down and the surface gets glassy, the fish can get super selective. At these times it is easy to view a fishes behavior under the fly. I switched flies at every rejection will I started catching consistently with a crippled calilbaetis floating emerger.