Hatch profile
Isonychia bicolor
Water-temperature trigger
Top fly patterns
Long-running hatch from June into October. Nymphs are strong swimmers and crawl out of the water to emerge — fish a swung wet fly through riffles.
Best rivers
Pennsylvania
Brodhead Creek
Jul 1 – Sep 30 · moderate
Pennsylvania
Loyalsock Creek
Jul 1 – Sep 30 · moderate
Pennsylvania
Upper Delaware River
Jul 1 – Sep 30 · heavy
New York
West Branch Delaware River
Jul 1 – Sep 30 · heavy
New York
Willowemoc Creek
Jul 1 – Sep 30 · heavy
New York
Esopus Creek
Jul 1 – Sep 30 · heavy
New York
Neversink River
Jul 1 – Sep 30 · heavy
New York
Rondout Creek
Jul 1 – Sep 30 · heavy
Virginia
New River
Jul 15 – Sep 30 · moderate
Virginia
Rose River
Jul 15 – Sep 30 · moderate
West Virginia
Elk River (headwaters)
Jul 15 – Sep 30 · moderate
West Virginia
North Fork South Branch Potomac
Jul 1 – Sep 30 · moderate
North Carolina
South Toe River
Jul 15 – Sep 30 · moderate
North Carolina
Chattooga River (upper)
Jul 15 – Sep 30 · moderate
Maryland
Big Gunpowder Falls (freestone upper)
Jul 1 – Sep 30 · moderate
New Jersey
Musconetcong River
Jul 1 – Sep 30 · moderate
Connecticut
Farmington River
Connecticut
Housatonic River
Jul 5 – Sep 25 · moderate
Vermont
Lamoille River
Jul 15 – Sep 20 · moderate
Other rivers with Slate Drake activity
Bield: Fish watches USGS water-temp gauges for your home water and pings you when conditions hit the 55–70°F trigger window.
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