Originating high in the Purcell Mountains and coursing 120 km through cedar-hemlock canyons to meet the Kootenay near Fort Steele, the St. Mary River is famed for its aggressive, surface-eating westslope cutthroat trout. Strict fly-fishing-only and catch-and-release regulations, combined with cold, aquamarine water and easy raft access from Cranbrook, create one of Canada’s most consistent dry-fly destinations.
**Upper Canyon (St. Mary Lake → Kimberley)** – steep boulder gardens and pocket water with eager cutties. **Middle Valley (Kimberley → Wycliffe)** – riffle-run glides, under-cut banks, and prolific stonefly hatches. **Lower Flats (Wycliffe → Fort Steele confluence)** – broad willow-lined bends perfect for drift-boats and autumn hopper action; this is the most-guided reach.
Native westslope cutthroat trout (25–40 cm, trophies 50 cm) dominate; migratory bull trout over 70 cm arrive from the Kootenay each July–September. Mountain whitefish school below riffles, while rainbow–cutthroat hybrids are rare thanks to strict stocking controls.
Skwala stones and March browns spark April surface activity. Late-June golden stones bring explosive bank-side eats, followed by PMDs, caddis and green drakes through July. Windy August afternoons drop spruce budworms and hoppers that cutthroat inhale in ankle-deep riffles. Bull trout prowl deep pools, ambushing fry, whitefish and smaller trout—swing big streamers once temps hit 10 °C.
A 9 ft 5-wt covers most dry-fly work; add a 7-wt sink-tip for bull-trout streamers. Typical summer rig: 12 ft 5X leader to a #10 foam golden-stone or #12 hopper with a #16 bead-head pheasant-tail dropper. Euro-nymph 10 ft 3-wts with 3 mm Perdigons during spring runoff. Cutthroat sit inches from shore—short, accurate casts and stealth trump distance.
“Peavine Flats” below Kimberley Golf Club offers evening caddis magic. “Skookumchuck Riffles” upstream of Wycliffe produce hopper-dropper action all August. “Horse Pool” near Fort Steele harbours late-season bull trout. Upper-canyon hike-ins above St. Mary Lake yield solitude and eager cutties on small attractors.
BC Highway 95A parallels 35 km of river with public pull-outs at Kimberley Riverside, Wycliffe Park and Savoy Landing. Forestry Road 3 follows the lower valley to Fort Steele. Floaters launch rafts at Wycliffe and take out at Fort Steele (18 km, 4–5 h at 20 m³/s). Winter anchor ice and sweepers require scouting before early-season drifts.
Flies: #10 foam golden-stone, #12 tan hopper, #14 elk-hair caddis, #16 PMD sparkle-dun, #8 olive circus peanut, #4 white/olive belly-scratcher. Leaders: 12 ft 5X mono for dries, 10 ft 4X fluoro for nymphs, 7.5 ft 0X for streamers. Felt soles are legal, but Clean-Drain-Dry protocols apply at AIS stations May–Oct.
Fly-fishing-only, single barbless hooks, and catch-and-release for trout safeguard the native cutthroat/bull-trout fishery. Elk Valley coal operations influence turbidity; the St. Mary River Water Users Coalition monitors sediment and temperature. Anglers can volunteer for annual redd counts and riparian willow plantings organized by the Elk River Alliance.
Spring runoff can top 120 m³/s—unwadeable. Bears frequent berry thickets; carry spray and make noise. Afternoon chinook winds gust 50 km/h; secure rafts. Winter shelf-ice collapses; wear a wading belt and pack dry clothes if fishing shoulder seasons.
**St. Mary Angler & Fly Shop** (Cranbrook) posts daily reports, rents rafts and issues Classified Waters Licences. **Kootenay Fly Shop & Guiding** (Fernie) carries Euro gear and provides shuttle service. **Michael & Young Fly Shop** (Vancouver) ships Elk/St. Mary dry-fly assortments and spare Spey tips.
Support the **Elk River Alliance**, **St. Marys Valley Rural Conservation Association**, and the **Steelhead Society of BC**. Donations fund temperature loggers, bank stabilization and education programs protecting the cutthroat stronghold.
St. Mary River from the outlet of St. Mary Lake downstream to the Kootenay confluence is **Classified Waters – Class II** 15 June – 31 October. Anglers need a basic BC licence plus a daily or annual Classified Waters Licence; daily quota 20 resident, 8 non-resident rod-days. **Fly-fishing-only, single barbless hooks, no bait or scent.** All cutthroat, rainbow and bull trout must be released; mountain whitefish limit five. Bull-trout-spawning tributaries close 1 Sept – 31 Oct—check in-season notices. Consult the BC 2025–2027 Freshwater Fishing Regulations Synopsis for full boundaries, quotas and emergency updates.