Golden stone flies are still around up and down the river. Some may flies have peaked (green drakes, gray drakes, March browns) and others are yet to peak ( brown drakes and flavs on the upper river). Afternoons will be the best times for finding the brown drakes and flavs.
The other happening that will begin its season is recreational floating. Going through Box Canyon and Big Springs to Mack’s Inn will have the biggest concentrations, but they will also be common through Harriman State Park to Riverside campground. Be patient with these folks as most of them have yet to form an etiquette. Gently explain to them that you realize they have a right to the river, but we appreciate you giving anglers present enough room to enjoy what they do. To be sure, you will learn a lot about human nature through these encounters.
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.
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.
Green Drakes are out on the lower river with best concentrations below Ashton Dam to above Chester backwaters. Although they inhabit many section of the river, this is the best hatch in terms of numbers. They may have peaked here, but there are enough to make a visit worthwhile. Days with higher relative humidity, little wind, and even overcast will bring out the best concentrations. But as with the feeding on stoneflies a few weeks earlier, they will become filled and head to the depths to digest. A strategy is to give them time to digest, then come back later with life form patterns, and you will have some action.
Here is some good info from Dr. Rob Van Kirk’s Water Status report filed yesterday for the Henry’s Fork watershed.
Water quality
Overall, water quality continues to be excellent throughout the watershed. Turbidity has increased a little at most locations over the past day or two due to rain but remains much lower than it had been during the peak of snow melt a few weeks ago. Water temperatures are in or slightly below the optimal range for rainbow trout watershed-wide. Dissolved oxygen concentrations are also optimal. Timing of aquatic insect hatches at Flat Rock, Pinehaven, Ashton and St. Anthony is staying around 1–4 days later than average but 1–3 days earlier than last year. Hatch timing at Marysville and Island Park Dam is 7–8 days later than average and about 1–3 days later than last year. I do not expect hatch timing to change much with respect to average for the foreseeable future.
Consider that Dr. Rob is talking about the peak of insect hatches. This means that a few insect are emerging now, but achieving peak concentrations are delayed.
The above photo shows The Tubs area above Mack’s Inn. Try pitching streamer patterns into these deep holes. You will find some relative solitude before recreational floating gets going.
Today there are more folks on the upper river than in the rest of Fremont County. Look at the attached photo to see anticipation camps on the river below Osborn Bridge.Today is also the last of the Henry’s Fork Foundation Henry’s Fork Days event sited at Last Chance. Harriman State Park opened to fly fishing a few days ago, and green drakes should begin hatching in numbers soon. If you are looking for them, they are most active on cool days having higher air relative humidity. Seems like we have had a lot of those days lately! They are getting going on the lower river along with golden stones and caddis and the number of anglers are less than on the river above.
The giant stonefly hatch is heading up the river but at a pace slower than last year. If you own a soft- sided boat ( rubber raft, etc.) a good trip considering active fish and lack of crowds, put in at the lower Mesa Falls access and float down to the Stone Bridge access just below the Warm River confluence. It is a beautiful trip, just beware of little Surprise Falls about a third of the way down the trip. Afternoon caddis activity is going on good up and down the river.
Headlines From Dr. Rob Van Kirk’s Water data report filed June 6th for the Henry’s Fork Drainage.
As expected, snowmelt was lower yesterday because of cooler temperatures and loss of remaining mid-elevation snow. Snow remains only at the highest elevations.
Natural streamflow was roughly constant yesterday at 110% of average, as Fall River and Teton River respond to the last gasps of high-elevation snowmelt.
Heavy precipitation in the forecast could temporarily increase streamflow again next week.
At an average outflow of 843 cfs, Island Park Reservoir gained 281 ac-ft yesterday and is 99% full. Outflow will continue to be reduced gradually as inflow decreases.
The big stone flies are out along the river from Ashton Dam down to Chester backwaters, but the same with fly fishers, wading and boating. It is likely the big bugs are also out in lower Cardiac Canyon just above the Warm River confluence. If you are looking to get away from crowds, here are a few locations that will help do so.
Park at the old Bear Gulch Ski area and walk down the service road to the river. When you arrive at the river, walk upstream for the best fishing.
From Riverside Campground walk downstream on the marked trail. The trail is adjacent to the river going almost to the west side of Hatchery Ford. The last out take for boats before Cardiac Canyon is on the east side of the river at this point. This place can also be reached by taking the West Hatchery Ford road from U. S. Highway 20.
Headlines from Dr. Rob Van Kirk’s Snow-Water Equivalent Report Compiled Yesterday
Temperatures were average over the holiday weekend, slowing snow melt a little; nonetheless, SWE is 36% of this year’s peak, compared with 44% of peak remaining on average.
Natural streamflow has dropped over the past four days to 121% of average.
At an average outflow of 1,349 cfs, Island Park Reservoir gained 122 ac-ft/day over the weekend and is 98% full, close to average for the date. Expect continued small outflow changes to manage fill.
The upper Snake River reservoir system is 82% full, compared with 79% full on average.
As of yesterday, none of the big stone flies are flying and egg laying around the river between Ashton Dam and Chester. Presenting big stone fly nymph, rubber leg, woolly bugger types, streamer and San Juan worm patterns are likely to bring the best chances of fishing success up and down the river for a while.
In the Island Park area, Buffalo and Riverside campgrounds will be open for the Memorial Day weekend. Some loops within each may be closed in order to dry out.
Big stonefly nymphs are migrating in the river from Cardiac Canyon on downstream, but if any are flying and egg laying, their numbers are small enough that trout are not yet attracted. Aquatic insect activity is several days behind across the entire Henry’s Fork drainage. Here is an item from Rob Van Kirk’s SWE report filed yesterday concerning aquatic insect activity in the drainage: “Timing of aquatic insect hatches is running around 2-6 days later than average in the upper watershed and 4-11 days later than average in the lower watershed. Given continued snow melt, increased cloudiness, cooler temperatures, and rain, I do not expect hatch timing to catch up to average any time soon.”
Back country road and campground openings are also behind for this time of the season. With Memorial Day weekend coming up, the Ashton/ Island Park Ranger District office will have the best information on road and campground openings/closures.
Any day now the giant then golden stone flies will be out along the lower river from Cardiac Canyon downstream to the Chester backwaters. Until these emerge, then fly and begin egg-laying activity, presenting nymph patterns of these will be effective. Caddis activity also abounds along this stretch of river. Discolored water persists from Warm River to Ashton Reservoir.
