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Fishing St Marys Lake: what the data says
244-acre lake near Montana. The lake tops out around 240 ft. The depth chart is built from real state fisheries GPS surveys, so the humps, channels and drop-offs you see are measured, not guessed. Here is how the season plays out for each species, straight from the data behind the map.
Brook Trout fishing at St Marys Lake
In spring, brook trout run shallow here, mostly 2 to 15 ft. Summer pushes them deeper, 10 to 30 ft, and winter fish settle into 3 to 20 ft. The spot to know is Shallow bay flat, a weed flat in about 22 ft of water that rates good for brook trout in winter. Plan around early morning and the evening in the warm months. Summer baits: a small spoon fished deep or a trolled lake-clear wobbler + worm gets it done.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 2 to 15 ft | dawn & dusk | Small inline spinner (gold), Tiny spoon |
| Summer | 10 to 30 ft | dawn & dusk | Small spoon fished deep, Trolled lake-clear wobbler + worm |
| Fall | 2 to 15 ft | midday & dawn | Small spoon (orange), Spinner |
| Winter | 3 to 20 ft | dawn | Small jigging spoon, Tungsten jig + plastic |
Cutthroat Trout fishing at St Marys Lake
Start shallow in spring: cutthroat trout sit in 3 to 15 ft that time of year. By summer they slide out to 10 to 35 ft, and by winter most fish are in 10 to 40 ft. If you only fish one area, make it Main-lake point: a point around 21 ft that scores prime in fall. Best bite is early morning and the evening. Tie on a trolled spoon (small) or a inline spinner and you're in the game.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 3 to 15 ft | dawn & dusk | Inline spinner (silver/gold), Small spoon |
| Summer | 10 to 35 ft | dawn & dusk | Trolled spoon (small), Inline spinner |
| Fall | 5 to 25 ft | dawn & dusk | Casting spoon, Inline spinner |
| Winter | 10 to 40 ft | dawn | Small jigging spoon, Marabou jig |
Rainbow Trout fishing at St Marys Lake
Spring rainbow trout on St Marys Lake hold shallow, usually 5 to 20 ft. By summer they slide out to 8 to 30 ft, and by winter most fish are in 8 to 40 ft. The spot to know is Break off the point, a drop-off in about 40 ft of water that rates prime for rainbow trout in winter. In summer the feeding windows fall in early morning and the evening. Summer baits: a dodger + spoon (deep troll) or a flutter spoon gets it done.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 5 to 20 ft | dawn & dusk | Inline spinner (silver), Small spoon |
| Summer | 8 to 30 ft | dawn & dusk | Dodger + spoon (deep troll), Flutter spoon |
| Fall | 10 to 35 ft | dawn & dusk | Casting spoon, Jerkbait over shoals |
| Winter | 8 to 40 ft | dawn | Jigging spoon, Tube jig (white) |
Notable structure
- Deep basin: deep basin, around 240 ft
- Shallow feeding flat: feeding flat, around 61 ft
- Secondary point: point, around 44 ft
- Break off the point: drop-off, around 40 ft
- Back-bay flat: weed flat, around 30 ft
- Shallow bay flat: weed flat, around 22 ft
- Main-lake point: point, around 21 ft
Common questions
How deep is St Marys Lake?
St Marys Lake is about 240 ft at its deepest point. The depth chart here comes from real state fisheries GPS surveys, so the contours reflect measured depths.
What fish are in St Marys Lake?
Anglers target rainbow trout, brook trout, cutthroat trout on St Marys Lake.
Where is the best fishing spot on St Marys Lake?
Main-lake point is the top-rated area: a point in about 21 ft of water that rates prime for cutthroat trout in fall. Open the map above to see every rated spot for each species and season.
When is the best time to fish St Marys Lake?
For brook trout, the summer bite is best in early morning and the evening. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.
Nearby waters
Mission Reservoir, In Part · Rattlesnake Lake #22 · Mcdonald Lake · South Meadow Lake · Fly Lake (Missoula) · Sanders Lake
See how St Marys Lake stacks up: best rainbow trout lakes in Montana · best brook trout lakes in Montana · best cutthroat trout lakes in Montana
Browse all Montana fishing maps or every water on DepthScout. Bathymetry credit: state fisheries survey programs. How we build these maps. For fishing guidance only, never navigation.