The 2025-2027 Region 4 synopsis lists the Lardeau River (management units 4-29/4-30) as No Fishing downstream of fishing boundary signs at the Trout Lake outlet, to fishing boundary signs approximately 600 m downstream near the confluence of Mobbs Creek (the Gerrard rainbow spawning sanctuary). Outside that closed reach, the river is exempt from the regional spring closure (Apr 1-Jun 14) and from the Nov 1-Mar 31 trout/char release, with a rainbow trout quota of 5 (any size) and a bull trout quota of 2 (any size). The listing includes tributaries by default unless one is separately listed (Asher Creek carries its own closure). Trout Lake itself closes northwest of a line about 1.5 km southeast of the village, Feb 1-May 31, and Trout Lake's tributaries are bull trout catch-and-release. Confirm the current synopsis before you fish.

NRCan's geographical names data and Wikipedia agree on the river's mouth at 50.24278, -116.95639, where it joins the Duncan River about 13 km upstream of Kootenay Lake. The local network model runs it at stream order 7, essentially full-river scale, over roughly 44 km from the Trout Lake outlet (Wikipedia's own figure, 43 km, matches closely). Channel-geometry data puts the median width at about 58 m, broad enough for a drift boat, the gradient at a nearly flat 0.28%, and mean annual discharge at roughly 59 m³/s, a high-volume river by Kootenay standards, though monthly flow swings hard: historic gauge records at Marblehead average around 13 m³/s in midwinter and 227 m³/s in June freshet.

The river runs in two distinct stretches. The upper 14 km, closest to Trout Lake, holds riffle water and deep pools over a bed of coarse sand, fine gravel and cobble to about 15 cm across, with log jams a recurring feature. The lower stretch carries fewer pools, a glacial-silt bed, and picks up volume through the summer from glacially fed side streams. Duncan Dam, completed in 1967, sits just above the Lardeau's mouth and eliminated a separate "Duncan River stock" of large rainbow that once spawned in the lower Duncan above this confluence. Since then, the Gerrard fish that spawn in the Lardeau have been the only stock feeding Kootenay Lake's trophy rainbow fishery. Don't confuse this river with Lardeau Creek, a separate, smaller water that feeds Trout Lake from the north; or with Gerrard Creek, a small named tributary a few kilometres from the Mobbs Creek confluence whose exact relationship to the spawning-closure boundary hasn't been confirmed.

The Gerrard story starts at the ghost town of Gerrard, right at the Trout Lake outlet, where the federal Department of Fisheries built a hatchery and egg-collecting station in 1912 after realizing the big trout showing up there each spring were a distinct, genetically isolated population spawning nowhere else. The station ran 1912-1932, then again 1939-1949 and in 1952, collecting eggs from 50 to 350 large females a year (James R. Irvine, BC Fisheries Management Report No. 72, 1978). A sawmill log boom near the outlet spawned its own problem: the "Handy" log jam grew for years and by 1923 was blocking so many fish that the federal government considered shutting the hatchery down for lack of spawners. It wasn't fully cleared until 1951. A 1966-67 fish-counting fence at Marblehead, downstream, tagged spawners that averaged 11 days and 4.6 km a day migrating upstream, almost entirely after dark.

That history is why the river carries the regulations it does today. The Region 4 synopsis closes a roughly 600 m reach from the Trout Lake outlet down to near the Mobbs Creek confluence to all fishing, permanently, protecting the spawning ground itself. Everywhere else on the river, the opposite logic applies: rainbow trout and bull trout numbers on the connected Kootenay Lake system have grown faster than the kokanee they eat, so the province runs a rainbow quota of 5 (any size) and a bull trout quota of 2 (any size) here, exempt from the usual spring closure and winter release, the same relief-valve approach used on Kootenay Lake's main body and paired with an angler incentive program that rewards turning in rainbow and bull trout heads. Fish it as a big-river float: broad, low-gradient water suited to swinging or stripping streamers through slots and along current seams rather than picking pocket water. Columbia River Adventures and Hatch Hunter Fly Shop both advertise guided bull trout trips on the connected lower Duncan River, with Lardeau and Argenta named as pickup points, though neither markets a Lardeau River trip by name.

Bull trout here fall under the same Kootenay Lake tributary system that opened a managed Duncan River bull trout fishery in 2019 as part of the same kokanee-recovery push. Handle every bull trout quickly and release it without a long fight; several are genuinely part of a recovering, still-fragile predator-prey balance, not a stable surplus.

No dedicated hatch survey exists for the Lardeau River itself. The forage story here is fish, not bugs: kokanee fry and adult kokanee are the reason the Gerrard grows as large as it does, with sculpin and juvenile whitefish filling out the same streamer-sized prey base found on the Duncan River and Kootenay Lake. Match that with large sculpin- and kokanee-pattern streamers such as the Dolly Llama or Woolly Bugger, or a Kootenay Lake Bucktail where trolling is the plan rather than casting. Behind the streamer program, the region's general mayfly, caddis, stonefly and terrestrial hatches cover the mountain whitefish and any incidental trout rising in slower water.

Highway 31 is the access corridor: a gravel road running north from Meadow Creek, at the north end of Kootenay Lake, along the Duncan and Lardeau rivers to Gerrard and the village of Trout Lake. It narrows to one lane in places with hairpin turns and drop-offs above Trout Lake, and isn't considered RV-friendly. No named public boat launch, put-in or trailhead specific to the Lardeau River itself has been confirmed; treat road and river access as something to verify locally, especially anywhere near the boundary signs marking the spawning closure.