When does the Early Black Stonefly hatch?

The Early Black Stonefly typically runs for 4 weeks. Peak emergence occurs in the midday.

What water temperature triggers the Early Black Stonefly hatch?

The Early Black Stonefly hatches when water temperature is between 38°F and 50°F, with peak activity around 42°F.

Black Stonefly #16-18, Black Beadhead Nymph #16, Small Black Stimulator #16.

Hatch profile

Capnia / Allocapnia

StoneflyMidday

Water-temperature trigger

30°F38–50°Fpeak 42°F80°F

Top fly patterns

Cold-water freestone stonefly, often seen crawling on snow banks. Trout key on the nymphs more than adults.

Other rivers with Early Black Stonefly activity

Bield Fish watches USGS water-temp gauges for your home water and pings you when conditions hit the 38–50°F trigger window.