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Rating depth structure for smallmouth bass.
Recent public catches load as you reach this section.
133-acre lake in Carbon County, Montana. The lake tops out around 120 ft. The depth chart comes from published agency bathymetric survey data, so the contours are survey-derived rather than computer-modeled. Below is the species-by-species picture, pulled from the same data the map uses.
Drawn out, this is 133 acres of water rimmed by 1.8 miles of bank. Nearly circular (index 1.1), so the story is the bottom, not the bank. 9% of the surface is littoral (under ~15 ft) — cover, weeds and forage water. Tip to tip the water measures near 0.7 mi with a 0.4-mi widest point. The water lies in Carbon County. For a second option, Sky Top Lakes (Park) lies 1 mi west.
Spring walleye on Cairn Lake hold shallow, usually 4 to 15 ft. They move out to 15 to 35 ft in summer and finish the year down in 20 to 40 ft. Put Main-lake point first on the milk run — a point near 1 ft that grades good for fall. The feeding windows run the evening and early morning. The summer box starts with a crawler harness on bottom bouncer or a deep crankbait (trolled).
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 4 to 15 ft | dusk & dawn | Main-lake point (1 ft) | 1/8 oz jig + minnow, Hair jig |
| Summer | 15 to 35 ft | dusk & dawn | open water | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 12 to 40 ft | dusk & night | Main-lake point (1 ft) | Jigging rap, Jig + big minnow |
| Winter | 20 to 40 ft | dusk & dawn | open water | Jigging spoon + minnow head, Rattle bait |
In spring, northern pike run shallow here, mostly 2 to 8 ft. Summer pushes them deeper, 8 to 20 ft, and winter fish settle into 5 to 15 ft. Shallow bay flat is the standout, a feeding flat at roughly 1 ft, rated prime for spring northern pike. Time it for early morning and the evening. You won't need more than a bucktail or a weedless spoon over cabbage most summer days.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | Shallow bay flat (1 ft) | #5 inline spinner, Spoon (red/white) |
| Summer | 8 to 20 ft | dawn & dusk | open water | Bucktail, Weedless spoon over cabbage |
| Fall | 6 to 18 ft | midday & dawn | Main-lake point (1 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Shallow bay flat (1 ft) | Tip-ups, Large jigging spoon |
Early season yellow perch use the shallows, holding in 3 to 12 ft. Expect a summer slide to 10 to 30 ft, then a winter hold in 15 to 35 ft. Put Shallow bay flat first on the milk run — a feeding flat near 1 ft that grades prime for spring. In summer the feeding windows fall in early morning. Tie on a drop-shot micro plastics or a small spoon tipped with worm and you're in the game.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Shallow bay flat (1 ft) | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 10 to 30 ft | dawn | open water | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 12 to 35 ft | midday | open water | Jigging spoon (small), Perch rig / spreader |
| Winter | 15 to 35 ft | midday & dawn | open water | Tungsten jig + spikes, Rattle spoon (small) |
In spring, smallmouth bass run shallow here, mostly 3 to 12 ft. Summer pushes them deeper, 10 to 30 ft, and winter fish settle into 20 to 45 ft. Main-lake point is the standout, a point at roughly 1 ft, rated good for spring smallmouth bass. Time it for early morning and the evening. You won't need more than a drop shot (goby/minnow) or a ned rig most summer days.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | dawn & dusk | Main-lake point (1 ft) | Ned rig, Tube jig |
| Summer | 10 to 30 ft | dawn & dusk | Main-lake point (1 ft) | Drop shot (goby/minnow), Ned rig |
| Fall | 8 to 25 ft | midday & dawn | Main-lake point (1 ft) | Jerkbait, Blade bait |
| Winter | 20 to 45 ft | midday | open water | Blade bait, Hair jig |
Start shallow in spring: rainbow trout sit in 5 to 20 ft that time of year. Warm water sends them out to 8 to 30 ft; cold water stacks them in 8 to 40 ft. Top water on the chart: Main-lake point, a point in the 1 ft range, good in spring. Fish it in early morning and the evening and you'll meet the bite. Throw a dodger + spoon (deep troll) or a flutter spoon until the fish tell you otherwise.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 5 to 20 ft | dawn & dusk | Main-lake point (1 ft) | Inline spinner (silver), Small spoon |
| Summer | 8 to 30 ft | dawn & dusk | open water | Dodger + spoon (deep troll), Flutter spoon |
| Fall | 10 to 35 ft | dawn & dusk | Main-lake point (1 ft) | Casting spoon, Jerkbait over shoals |
| Winter | 8 to 40 ft | dawn | open water | Jigging spoon, Tube jig (white) |
The spring pattern is a shallow one: lake trout in 10 to 40 ft. As the season builds they drop to 50 to 120 ft, wintering in 20 to 80 ft. Top water on the chart: Deep basin, a deep basin in the 120 ft range, prime in summer. Time it for early morning. Summer baits: a white tube jig (deep) or a magnum spoon on downrigger gets it done.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 10 to 40 ft | dawn & dusk | Main-lake point (1 ft) | Casting spoon over shoals, Jerkbait (shallow) |
| Summer | 50 to 120 ft | dawn | Deep basin (120 ft) | White tube jig (deep), Magnum spoon on downrigger |
| Fall | 10 to 50 ft | dusk & dawn | Main-lake point (1 ft) | Heavy casting spoon, Jigging rap over reefs |
| Winter | 20 to 80 ft | dawn | Break off the point (81 ft) | White tube jig, Airplane jig |
Cairn Lake also holds crappie (10 to 25 ft in summer), channel catfish (8 to 25 ft in summer), brook trout (10 to 30 ft in summer). Pick any of them on the map above for rated spots and bait picks.
Count 6 structure marks on this chart. The deepest, Deep basin, sits near 120 ft.
Season dates, license requirements, and size and bag limits for Montana waters are set by the Montana Fish, Wildlife & Parks — and special regulations can apply to Cairn Lake specifically, so confirm the current rules before you fish.
Check the official Montana fishing regulations →
Cairn Lake is about 120 ft (37 m) deep at its deepest point. The depth chart comes from published agency bathymetric survey data, so the contours are survey-derived rather than computer-modeled.
Anglers target walleye, northern pike, yellow perch, smallmouth bass, rainbow trout, lake trout, crappie, channel catfish, brook trout on Cairn Lake. This isn't a survey of the water — none is published for it — but an informed estimate from the species common to the region, narrowed by this water's depth, size and each species' range.
Deep basin is the top-rated area: a deep basin in about 120 ft of water that rates prime for lake trout in summer. Open the map above to see every rated spot for each species and season.
For walleye, the summer bite is best in the evening and early morning. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.
Fishing on Cairn Lake is regulated by the Montana Fish, Wildlife & Parks. Check the official Montana regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.
Sky Top Lakes (Park) 1 mi · Medicine Lake 1 mi · Stephanie Lake 2 mi · Rough Lake (Park) 2 mi · Lowary Lake 2 mi · Granite Lake (Carbon) 2 mi · Lone Elk Lake 2 mi · Echo Lake (Carbon) 2 mi · Aero Lake, Upper 2 mi · Dewey Lake 2 mi · Fizzle Lake (Windy Lake/Dead Horse Lake) 2 mi · Fossil Lake (Carbon) 3 mi
See how Cairn Lake stacks up: best smallmouth bass lakes in Montana · best walleye lakes in Montana · best northern pike lakes in Montana · best crappie lakes in Montana
More water nearby: Carbon County fishing maps (65 charts). Browse all Montana fishing maps. See every water on DepthScout. Bathymetry: published agency survey data. How we build these maps. Fish here with a sonar unit that logs? Send us your depth data and we'll improve this chart, credited to you. For fishing guidance only, never navigation.