Henry’s Fork, June 27th, 2023
Upper Coffee Pot Area
Water Quality and Insect Hatch Information From Dr. Rob Van Kirk’s Henry’s Fork Watershed Report of Today
Overall, water quality continues to be excellent throughout the watershed. Turbidity continues to decrease across the watershed. Water temperatures yesterday were near to slightly below average throughout the watershed. Temperatures were within the optimal range for rainbow trout most of the day in most river reaches. Dissolved oxygen concentrations are optimal.
Timing of aquatic insect hatches at Flat Rock, Ashton Dam and St. Anthony is 1–4 days later than the 2014–2022 average but 1–4 days earlier than last year. Hatch timing in the river reach between Island Park Dam and Pinehaven is 5–6 days later than average but at or a few days ahead of that in 2022. Hatch timing lags average by the largest margin at Marysville, where it is 9 days later than average.
Rob Van Kirk, Ph.D.
Senior Scientist
P.O. Box 550
Ashton, ID 83420
208-881-3407 CELL
Dr. Rob Van Kirk’s information above explains why fishing is better on some parts of the river than others. For example a good population of big stoneflies remain in Box Canyon, but on cool, cloudy days streamer fishing produces best. Golden stoneflies are coming out up and down the river., Gray drakes and flavs are showing up during PMs on the river below Ashton Dam. The fabled green drake hatch is yet to be significant in the Harriman State Park reach and is declining on the lower river.
The lower Coffee Pot area will one of the better locations to find relative solitude on the river. The Henry’s Fork giant stonefly hatch ends there, and golden stone fly, PMD and caddis activities can bring on good fishing.