Hatch Guide · Mayfly (Baetidae)
Blue Wing Olive
One of the most important hatches in North American fly fishing. BWOs emerge on overcast, drizzly days from early spring through late fall — a long season that rewards anglers who plan around cold fronts. Fish key on the duns drifting in the film.
Peak months: AprilMaySeptemberOctoberNovember
Top fly patterns
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Month-by-month activity
Number of rivers where the Blue Wing Olive hatch is active each month.
Rivers where Blue Wing Olive hatches
Farmington River
Trout Management Area below Riverton — catch-and-release artificial-only year-round. Lower river sto…
Housatonic River
Catch-and-release TMA between Cornwall Bridge and Boardman Bridge. Hatches: caddis, Hendricksons, su…
Salmon River
Atlantic Salmon Broodstock area — special regs apply. Heavily stocked sections.
Willimantic River
TMA section near Willimantic. Spring and fall stocking.
Naugatuck River
TMA section. Improving water quality post-cleanup.
Yantic River
Spring stocked. Smaller water, less pressure.
Deerfield River
Cold tailwater below Fife Brook Dam (Florida, MA) plus the Mohawk Trail water. Dam releases drive fl…
Westfield River
Wild trout freestone river in the Berkshires. West Branch holds native brookies in upper reaches. St…
Battenkill River
Classic wild brown and brook trout river — no stocking, technical fish, clear water. Cooler than the…
Upper Delaware River Active now
Big tailwater-influenced system (West and East Branches plus the main stem) holding wild rainbows an…
Beaverkill River
The birthplace of American dry-fly fishing. Classic Catskill freestone water with Quill Gordon, Hend…
Ausable River
Classic Adirondack freestone river with wild brookies in upper reaches and browns and rainbows in th…
Esopus Creek
NYC watershed tailwater — Tunnel Portal releases cold water from the Schoharie Reservoir, keeping te…
Penns Creek
Limestone-fed wild trout stream famous for its Green Drake hatch in late May. Catch-and-release sect…
Brodhead Creek
Historic Pocono trout stream. Wild and stocked fish. Good access throughout. Classic Hendrickson and…
Gallatin River
Classic freestone river paralleling Highway 191 through the canyon south of Bozeman. Wild fish in th…
Madison River
One of Montana's legendary Blue Ribbon rivers. PMD, caddis, and salmonfly hatches make June and July…
Missouri River
World-class tailwater below Holter Dam near Craig. Midge and BWO hatches year-round; PMD and trico d…
Blackfoot River
Immortalized by Norman Maclean's A River Runs Through It. Recovered wild fishery with strong stonefl…
Big Hole River
One of the last wild arctic grayling rivers in the lower 48. Blue Ribbon trout water with massive sa…
Yellowstone River
The longest free-flowing river in the lower 48. Paradise Valley section near Livingston is prime Blu…
Bitterroot River
Scenic freestone river in the Bitterroot Valley south of Missoula. Good caddis and PMD hatches. Nati…
Clark Fork River
Recovering river through Missoula and western Montana. Bull trout present — handle with care. Good c…
Snake River
Pure wild Snake River fine-spotted cutthroat trout in a spectacular Teton backdrop. Float-fishing th…
North Platte River
The famous Miracle Mile below Seminoe Reservoir — cold tailwater holding large rainbows and browns. …
South Platte River
Gold Medal water through Cheesman Canyon and the Dream Stream above Eleven Mile Reservoir. Highly te…
Fryingpan River
World-class Gold Medal tailwater below Ruedi Reservoir near Basalt. Massive midge and PMD hatches. M…
Arkansas River
Gold Medal freestone river through the Arkansas Valley. Good caddis and PMD hatches. Wade fishing be…
Roaring Fork River
Gold Medal freestone and tailwater water through Aspen and down to Glenwood Springs. Strong PMD, cad…
Blue River
Gold Medal tailwater below Dillon Reservoir in Silverthorne. Heavily fished but holds large fish. Mi…
Cache la Poudre River
Colorado's only federally designated Wild and Scenic River. Freestone character through Poudre Canyo…
Henry's Fork
The Railroad Ranch reach through Harriman State Park is among the world's greatest dry-fly fisheries…
Silver Creek
Spring creek near Hemingway's Sun Valley. Crystal clear, spring-fed water with massive, selective tr…
South Fork Boise River
Cold tailwater below Anderson Ranch Dam. Strong midge and PMD hatches. Bull trout present — handle c…
Salmon River
The River of No Return — a wilderness canyon river through central Idaho. Wild steelhead and chinook…
Deschutes River
Oregon's crown jewel. Wild redsides and summer steelhead in a dramatic canyon. Salmonfly hatch in la…
Rogue River
Wild and Scenic River with famous steelhead and salmon runs. Spring Chinook and summer steelhead att…
McKenzie River
Home of the McKenzie River drift boat design. Gin-clear spring-fed water with wild rainbows. Skwala …
Metolius River
Spring-fed river emerging fully formed from the base of Black Butte. Catch-and-release artificial on…
Yakima River
Washington's premier trout river — Blue Ribbon water through the canyon below Cle Elum. Skwala hatch…
Green River
World-class tailwater below Flaming Gorge Dam. Sections A, B, and C offer different water types. Pro…
Provo River
Gold Medal tailwater from Jordanelle Reservoir through Provo Canyon. Midge and BWO year-round; PMD a…
San Juan River
Year-round Gold Medal tailwater with consistent flows below Navajo Dam. The Texas Hole no-kill stret…
Au Sable River
Michigan's most famous trout river — spring-fed, clear water through northern Michigan pines. The He…
Pere Marquette River
Blue Ribbon wild trout and steelhead river through northern Michigan. Spring steelhead and fall chin…
Watauga River
Cold tailwater below Watauga Dam. Year-round fishery with strong sulphur, caddis, and yellow sally h…
Davidson River
Gem of the Southern Appalachians in Pisgah National Forest. Wild trout in clear mountain water. Hatc…
Rose River
Remote wild trout stream in Shenandoah National Park foothills. Native brook trout in upper reaches,…
Hat Creek
Spring-fed wild trout fishery below PG&E powerhouse. California Wild Trout Program water with artifi…
Fall River
Boat-access-only spring creek in the Fall River Valley. Flat, clear water with massive, selective wi…
How to fish the Blue Wing Olive
Dead-drift a size 18–22 Comparadun or CDC Dun in the film. Fish often feed sub-surface on emerging nymphs just before adult activity becomes visible. Tighten your tippet to 6X.
Frequently asked
When does the Blue Wing Olive hatch?
Peak emergence: April, May, September, October, November. Timing varies by elevation, latitude, and water temperature.
What flies match the Blue Wing Olive hatch?
Top patterns: Parachute Adams (size 14-20); Blue Wing Olive (Comparadun) (size 18-22); Pheasant Tail Nymph (size 12-20); Rainbow Warrior (size 16-20).
What rivers have a good Blue Wing Olive hatch?
Blue Wing Olive hatches are documented on 50 rivers including: Farmington River, Housatonic River, Salmon River, Willimantic River, Naugatuck River and 45 more.
How do I fish the Blue Wing Olive hatch?
Dead-drift a size 18–22 Comparadun or CDC Dun in the film. Fish often feed sub-surface on emerging nymphs just before adult activity becomes visible. Tighten your tippet to 6X.
What is the Blue Wing Olive?
One of the most important hatches in North American fly fishing. BWOs emerge on overcast, drizzly days from early spring through late fall — a long season that rewards anglers who plan around cold fronts. Fish key on the duns drifting in the film. Family: Mayfly (Baetidae).
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