Although the Smith River is a smaller volume freestone river, it has suprisingly prolific hatches. The Smith is a lower elevation system relative to some of the larger rivers in Southwest Montana and many of its hatches occur a bit earlier as a result. The best early season hatches occur just before, during and after runoff. Anglers can often enjoy some great dry fly fishing in the pre and post runoff windows. Summer fishing is often dependent on water temperatures but terrestrial fishing can be excellent when water temperatures are cool. Strong terrestrial fishing extends into the fall along with some nice fall blue-winged olive hatches in October.
Blue Winged Olives (BWOs)
Beginning in late March and lasting through May and again in mid-September lasting well into October, these mayflies can hatch on any day during those two seasonal windows. Overcast days may see the strongest emergence, especially on the river downstream from the confluence with Rock Creek all the way down to where Deep Creek joins the Smith River. Sunny days can experience very strong hatches as well, but the ideal BWO day on the Smith River is overcast, with scattered showers, and air temps in the low 50s. Spring BWOs range from size 14 to 16 and fall BWOs range in size from 16 to 22.
Western March Browns
March Brown hatches on the Smith River are very sporadic. They can hatch on the entire length of the river in late- April and can be seen throughout May as well, but conditions must be ideal—overcast, water temperatures between 44 and 48 degrees F, and very light winds. If these conditions on the Smith River occur, a large emergence of March Browns can happen, making these large mayflies easy pickings for hungry trout. March Browns on the Smith River range in size from 12 to 16, with most being size 14.
Skwala stoneflies
The earliest stonefly hatch of the season, the skwala, emerges in random fits and spurts on the Smith River. Unlike salmonfly and Golden stonefly hatches where hundreds of adults can be seen fluttering in the air, a skwala emergence is subtle with only a few adults spotted airborne. But because these large insects hatch early in the season, opportunistic trout may rise to a well-presented dry fly. Most adults are size 8 and 10. Skwala nymphs are active year-round and most stonefly nymph patterns can imitate a skwala.
Caddis
Caddis on the Smith River hatch from late April through August, with strong hatches in early May, June, and July. The Smith River is home to a large amount of caddis species. Attempting to name them all would be cumbersome and not necessary for catching more fish. Caddis nymphs on the Smith River are active year-round and run from size 10 to 22. In late summer, evening caddis hatches provide camping anglers an enjoyable end to a special day floating the Smith River.
Salmonflies
Depending on when snowmelt runoff occurs, the salmonfly hatch on the Smith River can be a boon or a bust to anglers floating and camping on the river. A salmonfly hatch on the Smith River occurs over the course of a few days, and in some years a few weeks. Nymphs crawl to bankside structure and remove their outer shell—also known as their shuck. When this occurs an adult insect, complete with legs and wings, emerges. This typically occurs when water temperatures range between 54 and 58 degrees F, however this can also coincide with the start of snowmelt runoff. Fortunately, trout on the Smith River are accustomed to muddy water and can feed heavily when river clarity is poor. Weather, sunlight, and streamflow are all factors in the quality of fishing during a salmonfly hatch. Nymphs and adults (dry flies) range in size from 4 to 8. Salmonflies can hatch on the Smith River in late May or early June.
Golden stoneflies
On the Smith River Golden stoneflies provide plenty of action for dry fly anglers. These insects are size 8 to 12 and usually emerge slightly later than salmonflies. In some years they can hatch in early June and last into mid-July, a Golden stonefly hatch occurs in the same sequence as a salmonfly hatch, however golden stoneflies are smaller. Golden stoneflies are equally important to trout as salmonflies, they just don’t have the same celebrity status because they are the second species of stoneflies to hatch after runoff.
Yellow Sally stoneflies
These stoneflies may hatch concurrently with salmonflies and Golden stoneflies. Often mistaken for caddis or PMDs this small stonefly is a crucial part of a Smith River trout’s diet. Yellow Sally stonefly nymphs become active in early June, with adult insects hatching from early-June well into July. Yellow Sally nymphs range in size from 8 to 16, with size 10 and 12 being the most common. Because adult Yellow Sallies have very sporadic flying habits, trout rarely key on them making fishing dry flies difficult, but the nymphs are consumed on a daily basis.
Brown and Green Drakes
Drakes, both brown and green, hatch on the Smith River in June. Drakes are large mayflies, hatching when the water temperature hovers around 55 degrees F. Brown drakes begin to be active around 50 degrees, but it isn’t until 55 or 56 degrees F that enough adults hatch on the Smith River to entice trout to rise. Because the Smith River carries a lot of natural sediment, brown drakes are more prevalent than green drakes as brown drake nymphs prefer very fine sand and gravel. Most adults are size 14, with a few size 12 and 16 naturals on occasion.
Pale Morning Duns
These summer-time mayflies hatch in abundance on the Smith River. Pale Morning Dun (PMDs) begin to hatch in mid-June and last all through July. Primarily found in the river’s riffles and longer runs, PMDs emerge when water temperatures hit 58 degrees F. PMDs hatch on sunny or overcast days on the Smith River and they can hatch in either condition. Nymphs are available to trout year-round, but during a hatch, the hatching insects require time to allow for their wings to dry before taking flight, therefore being easily available to a sipping trout. Most PMDs are size 14 and 16, with size 16 being the most common.
Spruce Moths
Emerging as early as mid-July or as late as mid-August, flights of hatching spruce moths cannot be mistaken for anything else. Fluttering near pine trees and bankside bushes, Smith River trout can be overly opportunistic during a strong spruce moth emergence, creating plenty of dry fly fishing opportunities for anglers lucky enough to be fishing the Smith River in late July or August. Most spruce moths are size 14 or 16.
Trico mayflies
Although not a major hatch on the Smith River, tricos offer something for anglers desiring small fly, technical dry fly fishing. Tricos usually hatch at sunrise in late July and throughout August. An emergence rarely lasts longer than a few hours. Adult tricos swarm in mating swirls above the water, after mating they fall to the water and die, creating “spent” mayflies, also called “spinners” by many anglers.
Terrestrials: Grasshoppers, ants, and beetles
As the heat of summer grows and hatches become more sporadic and less predictable, trout look to land-based insects for food. Grasshoppers, ants, and beetles dominate a trout’s diet by late July. Having been blown into the river these land-dwelling insects are a common occurrence on the Smith River. Once on the water they become easy prey for hungry trout. Most grasshoppers are sizes 8 to 12 and most ants and beetles are size 14 to 18. Colorations vary but natural tones like gray and tan tend to fish better than bright colors.
October caddis
October caddis can hatch as early as late September and will typically peak in late October. Compared to other hatches, an emergence of October caddis is limited to a few flying insects in a given section of the river. But an opportunistic trout may feast on one of these large caddis species if it happens to float by at that same time a fish feels hungry. Most October caddis are size 8 to 10.