Boise River South Fork offers some of the best fly fishing in a state renowned for Blue Ribbon trout fisheries. Trout populations are supported by an abundance of mayfly, stonefly, and caddisfly hatches. Major fly hatches for Boise River South Fork are listed in the following hatch chart.

Mayflies, stoneflies, caddisflies and midges are the four main groups of aquatic insects that trout feed on in Boise River South Fork. There is also a Cicada hatch mid June. The hatch chart below lists each major fly hatch by date with respective fly sizes to “match the hatch”.

Boise River South Fork Fly Hatches

Even though aquatic insects begin hatching in late April, the action really doesn’t get underway until the end of May when the South Fork opens to recreational angling. During May and June water levels are high and float fishing is the norm. If you’re set on wade fishing, you may want to postpone your trip ’till early fall when flow subside.

During early June Caddisflies are the name of the game and you’ll see them emerging or hovering just above the surface throughout the day. Caddis hatches continue through mid July. Some of the more productive flies for matching caddis hatches include X-Caddis, Elk-hair Caddis, and Emergent Sparkle Pupae (#14-16).

If you manage to time your trip during the month of June come prepared to fish the cicada hatch. Some of the best fishing you’ll experience on the Boise South Fork will occur when cicadas are out in force, so come with a pocketful darker-colored cicada patterns. Fish a #6-8 Royal Stimulator during a cicada blitz and you’ll be reeling in lunkers nonstop.

Golden Stones and Salmonflies also begin hatching in June. Large Orange Stimulators, Foam Stones, and Madam Xs are a few of the more productive patterns for targeting stonefly hatches on South Fork.

Just as stonefly and caddis hatches begin to dissipate, Pale Morning Duns swing into full gear. Pink Alberts—one of the more important hatches on South Fork—also start appearing early afternoons in early July when air temperatures rise above 80-degree fahrenheit and they continue through August.

Sparkle Duns, cripples, Compara-duns and a good ole Parachute Adams, are your go-to flies for PMD hatches. If you arrive during a Pink Albert hatch, a #16 emerger pattern with wings exposed will get the trout biting subsurface. If trout are taking flys off the surface, we recommend a #14-16 Pink Albert Thorax or Pink Cahills.

As summer gives way to fall, Blue-winged Olive (Baetis) hatches take center stage—and some years they can be massive. Fall baetis hatches provide some of the best dry fly action on the South Fork the entire year. You’ll find abundant baetis hatches September through November, then again February and March.

Early spring, on wet rainy days when there’s still a chill in the air, is one of the best times to fish the hatches as large trout will be rising to the surface to feed. A few of the more productive baetis imitations include Parachute Adams, Baetis Compara-duns, and Thorax Baetis.

In addition to mayfly, caddis and stonefly hatches, anglers will find strong midge hatches from late fall through early spring. When trout aren’t surfacing, nymphing midge imitations such as a Zebra Midge or Copper Johns will usually get some takers. If trout are rising to the surface to dine on adult midges, standard Griffith Gnat patterns are your best bet.

If you’re going to be braving the cold, nymphing and streaming is where it’s at when fish aren’t coming to the surface. During this time of year anglers report stripping a Conhead Blossom Special or Sex Dungeon is most effective. You should also fish the slower moving pools using Leech and Girdle Bug patterns in the #4-6 size range.

In the later season when flows are low (below 400 cfs) trout become a little more guarded in their feeding behavior. The South Fork is still fishable but you need to have the right presentation to attract the attention of trout. This time of year sight fishing is popular and a standard PMD or Elk Hair Caddis pattern is your best shot at landing some descent catches.

If you want to catch the biggest of the South Fork’s residents, stripping streamers is the way to go, especially in the fall. Conehead Blossom Specials and Sex Dungeons are two of my all time favorite flies for getting the most finicky fish biting.