Intro | System | Hatches | Seasons
Hatches
At least six major mayfly hatches and a wide variety of caddis hatches occur between March and November on the South Fork. Midges hatch year-round and provide excellent dry-fly fishing on the sections open for fishing during the winter. On top of that, the South Fork produces some of the best stonefly hatches in the West, especially the giant salmonfly that normally emerges in early July.
Brown trout are most common in the lower river. Because they cannot interbreed with native cutthroats and their population is stable, they are not seen as a threat to the native cutthroat trout.
Mayflies. The dry-fly fishing season usually gets under way when the Pale Morning Duns emerge in late June or early July. These prolific mayflies can emerge into October. PMDs carpet the water in August, and the hatches are especially heavy on cloudy, cool days. South Fork PMDs have a definite pinkish cast.
A pink Parachute Cahill in #16-18 is the top choice during the PMD hatch. Thorax patterns and no-hackles in the same color are also very effective. If the fish are selective, you'll also need a variety of emergers and cripples. My favorite is a PMD Cripple with a white upright wing for better visibility. The same patterns are effective on the other mayfly hatches, but you need to change the size and color to match the insect. I've also found a spinner to be an excellent choice in the mid-morning and evening hours. These spent-wing patterns are tough to see. Sometimes I use a spinner or emerger as a dropper attached about a foot below a parachute pattern.
By late August you'll start to notice good numbers of Western Quill Gordons (Epeorus albertae) mixed with the PMDs. These mayflies are slightly larger than the PMDs and a little darker in color.
One of the best late season hatches is the Mahogany Dun (Paraleptophlebia bicornuta). Some anglers mistake them for PMDs because they are about the same size, but the body and wings are much darker. These mayflies continue to emerge into early October.
Tiny Blue-winged Olives (Baetis #20-22), are the most prolific and dependable mayflies (no matter what the weather is like) during late autumn and early spring. I've experienced some of the best dry-fly fishing on cold, snow-filled days.
It is not unusual to see Callibaetis spinners on the water. These medium-size mayflies abound in lakes, sloughs, and slow-moving spring creeks. There are numerous sloughs and back channels on the South Fork providing perfect habitat for these speckle-winged mayflies.
When the sun gets low in the sky in July and August it is time for the almost nightly caddis hatch and egg-laying flight. The author's Spent Caddis or Craig Mathews' X-caddis are two productive patterns.
Caddis. Anglers who like to fish during the evening hours in late July and August will see blizzard-like hatches and egg-laying flights of these active aquatic insects. There are many species of caddisflies on the river. The most common are the net-building Speckled Sedge (Hydropsyche) and the case-building Grannom (Brachycentrus). The giant October Caddis can also produce some explosive rises on bright autumn days. There usually aren't a lot of these big insects on the water, but since they can range as large as a #6, the trout really get after them.
Hair-wing caddis patterns, such as the Elk-hair Caddis, can be very productive, especially if casting from a drift boat. The E-Z Caddis is the best pattern I've found. It floats low in the film, has an Antron body and underwing with a partridge overwing, and a parachute-post wing. The Antron produces a very realistic brightness, and the partridge wing holds its shape even after it gets wet. A floating E-Z Caddis with a caddis-emerger pattern as a dropper provides a deadly combination when caddis are on the water. The trout will often hold under structure, so when you are fishing from a boat and casting up against the bank, I've found that giving the fly a little twitch can entice them out to take a look.
Stoneflies. Unlike most other tailwaters, the South Fork produces some incredible stonefly hatches, including the giant salmonfly (Pteronarcys). The big salmonflies usually start to emerge on the lower river about the first of July. The hatch moves upstream a few miles a day and reaches the Palisades Dam by mid-July. Because river flows can fluctuate from year to year, this hatch may deviate by two or three weeks each year.
The smaller Golden Stones and little Yellow Sallies follow the big bugs, providing good dry-fly action throughout July and into early August. You'll need some high floaters, such as the Kauffman's Stimulator, as well as some low-profile patterns. In recent years foam-bodied flies have been the rage, and for good reason. They seem to outproduce everything else, not only during the stonefly hatches, but as an attractor pattern all through the season.
A stonefly phenomenon that I have not witnessed on any other river occurs on the South Fork. In September when the flows are reduced, a #8 or #10 dark amber stonefly emerges that creates some explosive action on floating foam-bodied patterns. As the flows drop and new rocks are exposed on the bank, the nymphs crawl out to transform into adults. These adults do not have the appearance of normal stoneflies, however, because their wings are abnormally short, less than one-half their body length. These lively adults, incapable of flying, race over the rocks and across the water along the margins of the river. Chernobyl Ants and other foam patterns work great when you cast them at the edge of the water and twitch them back with an erratic retrieve. My favorite pattern is called the Green Machine, which is a two-tone foam fly with a pale underbody, brown rubber legs, and a short elk-hair wing.
Midges. As in most other tailwater rivers, midges are the most abundant aquatic insect. They emerge throughout the year, but are most prolific during the cold winter months. Most of the larger mayflies and caddis hatches are over by mid-October and the trout really begin to key in on the smaller insects. The slicks, quiet pools, and tailouts are the best spots to find midge-feeding trout. They usually pod up as they softly sip the tiny flies. The trick is to try to pick off the trout feeding at the edge of the pod. If you hook a trout in the middle of the group, you'll risk putting down the entire pod of fish.
Like caddisflies, the midge's pupal stage is usually the most important for the angler. For that reason, I like to tie on a high-riding pattern such as a Griffith's Gnat, and tie a midge pupa as a dropper about a foot off the hook bend. That way if I see the top fly move or hesitate, or if I see a rise or boil near the dry, I can set the hook. I like to tie my midge pupa patterns very lean, with a thread or biot body and a touch of dubbing or soft hackle at the hook eye. The best colors are gray, dark olive, or rusty brown.
Mike Lawson is former owner of the Henry's Fork Angler. His latest book is Spring Creeks, published by Stackpole Books. He lives in St. Anthony, Idaho.
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