Fishing Reports

Henry’s Fork, May 24th, 2024

Looks like the big stoneflies will be laying low until Memorial Day itself. In fact, a lot of insects ( excepting midges and BWOs) will be doing the same because of snow showers coming and going likely for the next few days. When weather warms up, as predicted for Monday, there will be a lot of fly fishers wading and boating on the river from lower Cardiac Canyon downstream to Chester. So here are a few locations to try where a minimum of fishing company will be present.

Bear Gulch requires walking from the old ski area parking lot, no quite a mile, to the river. Some of the thickest and earliest giant and golden stone fly hatches on the entire river happen here, and hard sided boats of any kind are very rare because the slide access below Lower Mesa Falls is prohibited to such. Expect to see some rafts passing through. Allow a few days of warm weather and other great boat- free and minimum wader locations will see the big stoneflies become active. First is above the river in Mesa Falls State Park. Walk upstream above the Park, and fish some great boat-free water. Another is the river above the signed West Hatchery Ford road going off Highway 20.. This side of the river is almost free of boats and not many wading anglers. The reason is that the boat take-out location is on the more popular east side of the river and closed to boating beginning right below. Walk upstream on an old game trail for a while to get above the cliffs and fish as long as time permits. Another walk-in only location is around Sheep Falls. The road to this area is sign and just downstream from the West Hatchery Ford Road.

As the hatch moves upstream, we will keep track of its progress. With warming weather and sufficient time, such as Box Canyon and Coffee Pot will feature their share of active big stone flies. By then choosing a great location almost anywhere on the Henry’s Fork will become more complicated as other great insect hatches will begin!

Some Details From Dr. Rob Van Kirk’s SWE Report for the Henry’s Fork Drainage Filed Yesterday, May 22nd.

Mean temperature yesterday was 8 degrees F below average, and precipitation was recorded at only one station. That kept snowmelt rates low and water-year total precipitation at 99% of average. Net change in snow water equivalent (SWE) was 0.2 inches of melt, compared with 0.5 inches on average. Remaining SWE is 53% of this year’s peak, compared with 57% on average, and current SWE is in the 45th percentile for the date.

Weather forecasts call for continued below-average temperatures through Sunday, with precipitation possible every day. Mid-elevation snow will continue to melt as it did yesterday at slightly below-average rates. High elevations will likely gain new snow today and tomorrow. Long-term outlooks call for very warm and dry conditions starting early next week and continuing for the foreseeable future. That will accelerate snowmelt at all elevations.

Water Quality

Water quality improved again yesterday, as turbidity continued to drop at all locations except immediately downstream of Island Park Dam. Dissolved oxygen concentrations are above average in all river reaches, and water temperatures were within the optimal range for rainbow trout egg and fry development watershed-wide. Hatch timing is within 1–2 days of average at all locations and will slow by a day or so over the next few days.

Rob Van Kirk, Ph.D.

Science and Technology Director

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CEL

Henry’s Fork, May 18th, 2024

Big Time Trout Food

The stone fly hatch on the lower river is beginning right on time. From Ashton Dam down to the Chester Dam nymphs are crawling onto banks. It will take some warm weather to advance the hatch in numbers, molting to adults, and to fly over the river. So until warm weather arrives, big nymph patterns simulating these insects will be among the most effective to use as resident trout key on such patterns. During this week the hatch should advance, and we will provide information on best locations to enjoy it into Memorial Day weekend.

By any measure the big stone fly appearance ends the so called shoulder season on the river. From now on high interest applies to the season long advance of insect life which makes fishing the river so famous. We at Fly Fish Food-Jimmy’s will monitor this advance on the river and provide solid information on it throughout the season.

Water Quality Statement from Dr. Rob Van Kirk’s SWE Report for the Henry’s Fork Drainage Filed Yesterday, May 17th.

Water quality continues to be good throughout the watershed. Water temperatures and dissolved oxygen concentrations are good to excellent and near average for this time of year. Turbidity continues to drop in the Warm River to Ashton reach and is also starting to drop downstream of Fall River. I do not expect abnormally high turbidity anywhere in the watershed for at least a week. Hatch timing is within a day of average at all locations and is likely to stay very near average for the next few days. Cooler weather next week could slow things down a bit then, but I expect average timing for the salmonfly hatch watershed-wide. Salmon fly adults have just started emerging in the spring-fed locations such as Buffalo River and Warm River, indicating just a few more days before they begin to hatch in large numbers in the reach between Ashton Dam and Chester Dam.

Henry’s Fork, May 11th, 2024

The Henry’s Fork continues to offer the most consistent fishing of any area stream. Good caddis, BWO, and midge activities are reasons for great top water fishing not only on the lower river, but on the river above. Here the Last Chance area and above Coffee Pot rapids are good areas to try. For streamer and nymphing enthusiasts, Box Canyon is worth a try using streamers and fly rod jigs.

Here is some encouraging water quality information from Dr. Rob Van Kirk’s Henry’s Fork drainage SWE report filed yesterday.

Water Quality

As good as water quality was on Wednesday, it was even better yesterday. Water temperatures warmed just a hair, putting them within the optimal range for development of rainbow trout eggs and fry in all river reaches. Increased sunlight yesterday resulted in higher photosynthesis than we have seen in a week, increasing dissolved oxygen watershed-wide. Turbidity continued to drop yesterday, although that trend will be reversed today as snow begins to melt. I expect the highest increases in turbidity to occur downstream of Robinson Creek and Fall River, which are the two tributaries that will respond the most to mid-elevation snowmelt over the next week. Hatch timing is a day behind average at most locations after slowing down over the past five days. However, I expect aquatic insect development to accelerate a little as temperatures warm, putting it back at average to a day or so ahead of average by the end of next week. That means upcoming springtime hatches—including salmonflies and March Brown mayflies—should be right on time.