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Henry's Fork Regional Hatch Chart		Expand All

By Mike Lawson

May Flies

	Mar	April	May	June	July	Aug	Sept	Oct	Nov - Feb

Blue Winged Olive (Baetis, several species)

Brown Drake (Ephemera simulans)

Flav (Drunella flavilinea)

Gray Drake (Siphlonurus occidentalis)

Mahogany Dun (Paraleptophlebia bicornuta)

Pale Morning Dun (Ephemerella inermis)

Tiny Olive Dun (Plauditus punctiventris)

Speckled Spinner (Callibaetis ferrugineus)

Trico (Trycorythodes minutus)

Western Green Drake (Drunella grandis)

Western March Brown (Rhithrogena morrisoni)

Caddis Flies

	Mar	April	May	June	July	Aug	Sept	Oct	Nov - Feb

Grannom (Brachycentrus)

Spotted Sedge (Hydropsyche)

Other Caddis flies (Several Genera and species)

Stone Flies

	Mar	April	May	June	July	Aug	Sept	Oct	Nov - Feb

Golden Stonefly (Acroneuria, classenia)

Salmon Fly (Pteronarcys)

Small Stone Flies (Isoperla, alloperla)

Midges

	Mar	April	May	June	July	Aug	Sept	Oct	Nov - Feb

Midge (Chironomidae)

Blue Winged Olive (Baetis)	Nymph Type:	Swimmer	Hook Size:	18 20 22
Characteristics:	Two tails. Light to medium olive/gray body with light to medium gray wings.
Timing of hatches:	Mid-March through Early May, 12:00 PM until 3:00 PM and in the mid-summer around dusk, September through October, from 11:00 AM until 4:00 PM
Habitat:	Widespread on most sections of the Henry's Fork, Madison, Firehole, South Fork of the Snake and other local rivers and tributaries.
Comments:	Many species are multi-brood, meaning a species may produce two or more broods during the calendar year. The most important species emerge in the spring and again, in the fall. These mayflies produce exceptional dry fly fishing during these periods. Egg laying Spinners often crawl under the water to oviposit their eggs.
Patterns:	Pheasant Tail Nymph, Halfback Emerger, CDC Emerger, Paracripple, BWO Soft Hackle, BWO Nohackle, Sparkle Dun, Thorax, and Parachute Adams.

	Nymph Type:	Burrower	Hook Size:	10 11 12
Characteristics:	Three tails. Slender body. Yellowish tan to light brown with darker markings. Wings are mottled brown, and heavily spotted.
Timing of hatches:	Mid to late June, immediately following the Green Drakes. Duns emerge at or just before dusk. Spinners normally fall about the same time. Some trout will often feed on nymphs or emergers, others on duns and still others on spinners.
Habitat:	Very localized in the very slow sections of the Henry's Fork on the Harriman Park, the Gibbon in Yellowstone Park and other waters. Needs slow water with silt bottom.
Comments:	Brown drakes are very important on the slow sections of the Harriman Park downstream to Pinehaven. Nymphs can swim rapidly prior to emergence. The focal point of the emergence moves gradually upstream a day at a time. The overall emergence period is about two weeks. Brown drakes sometimes also emerge in the morning hours.
Patterns:	Brown Drake Nymph, Emerger, Cripple, Paradrake, Mike's Brown Drake, Brown Drake Partridge Spinner.

	Nymph Type:	Crawler	Hook Size:	14 15 16
Characteristics:	Three tails. Dark gray wings with medium greenish or brownish olive body.
Timing of hatches:	Late June through July. Duns usually emerge in the late afternoon. Spinners fall in the morning hours. Best activity occurs on cloudy, humid days.
Habitat:	Medium to fast water sections of the Henry's Fork, Madison, Yellowstone and other surrounding waters. Especially common on the Last Chance section of the Henry's Fork and the tailwater section between Ashton and St. Anthony.
Comments:	Flav’s closely resemble their larger cousin, the Western Green Drake. Hatches are sometimes sporadic and undependable. However, trout really love these robust mayflies and it doesn't take many to create a feeding frenzy. The duns emerge slowly on the surface making emergers and cripples top pattern choices.
Patterns:	Pheasant Tail Nymph, Flav Cripple, CDC Emerger, Flav Thorax, Slate Olive No-hackle, BWO Parachute.

	Nymph Type:	Swimmer	Hook Size:	10 11 12
Characteristics:	Two tails. Dark gray wings with heavy veination. The body is olive gray with dark brown markings. Spinners are more purplish with clear wings.
Timing of hatches:	June into early July. Duns emerge sporadically during mid-morning hours. Spinners fall in the late afternoon and evenings and sometimes mid-morning.
Habitat:	Slow to medium fast water. The Gray Drake is an important hatch on the lower Henry's Fork below Ashton, lower Fall River, the estuaries of the Madison and South Fork of the Madison entering Hebgen Lake, and the Upper Yellowstone River below Yellowstone Lake.
Comments:	The nymphs concentrate in the margins of the stream where they crawl out to emerge. Consequently, the duns are not nearly as significant as the spinners. The mating flights of the spinners creates superb dry fly fishing on the lower Henry's Fork. High water years provide the best Gray Drake activity.
Patterns:	Feather Duster Nymph, Gray Drake Nymph, Gray Drake Spinner, Parachute Adams, Gray Wulff, Adams Parawulff.

	Nymph Type:	Crawler	Hook Size:	16 17 18
Characteristics:	Three tails. Dark gray wings with streamlined, dark mahogany body.
Timing of hatches:	The most important emergence occurs in late August through early October. Duns emerge during mid morning while spinners fall in the later afternoon to early evening hours.
Habitat:	Slow to medium fast gravel bottom water. Mahogany Duns are common on the Harriman Park stretch of the Henry's Fork, the South Fork of the Snake and several other local waters.
Comments:	The Mahogany Duns provide some of the finest dry fly fishing of the late summer on the Harriman Park and other waters. There are a number of other species that emerge throughout the summer but the late season is the best. Emergence takes place at the surface making an emerging nymph pattern very effective when trout are rising.
Patterns:	Pheasant Tail Nymph, Mahogany Dun Emerger, Mahagony Dun Parachute, Mahogany Dun Thorax, Slate Tan Nohackle

	Nymph Type:	Clinger	Hook Size:	12 13 14 15 16
Characteristics:	Two tails. Dark gray wings with strong dark mottling. Body is dark olive brown to purplish black.
Timing of hatches:	Late spring from mid-April through early June. Duns emerge during mid-morning hours. Spinners fall in the evenings.
Habitat:	Medium to fast water with gravel or rocky bottom. Very common on most sections of the Henry's Fork. Late season species are also common on the Madison, Gallatin, and some waters in Yellowstone Park.
Comments:	March Browns provide exceptional dry fly fishing on the Henry's Fork in May and early June. Transformation from the nymph to the dun usually takes place under the water. Therefore, a soft hackle emerger fished deep can often bring good results. During cooler weather the duns will stay on the surface long enough to provide good dry fly action.
Patterns:	Pheasant Tail Nymph, Pheasant Tail Soft Hackle, March Brown Emerger, Quill Gordon, Slate Olive Thorax, Slate Olive Nohackle.

Henry's Fork Regional Hatch Chart

May Flies

Blue Winged Olive(Baetis)

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Stone Flies

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Blue Winged Olive
(Baetis)