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Fishing BIG THERRIAULT LAKE: what the data says
51-acre lake near Montana. The lake tops out around 80 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. What follows comes from the same scoring engine that paints the spots above.
Rainbow Trout fishing at BIG THERRIAULT LAKE
Spring rainbow trout on BIG THERRIAULT LAKE hold shallow, usually 5 to 20 ft. They move out to 8 to 30 ft in summer and finish the year down in 8 to 40 ft. The spot to know is Main-lake point, a point in about 16 ft of water that rates prime for rainbow trout in spring. Plan around early morning and the evening in the warm months. 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) |
Yellow Perch fishing at BIG THERRIAULT LAKE
Start shallow in spring: yellow perch sit in 3 to 12 ft that time of year. They move out to 10 to 30 ft in summer and finish the year down in 15 to 35 ft. If you only fish one area, make it Shallow bay flat: a weed flat around 7 ft that scores prime in spring. Plan around early morning in the warm months. A drop-shot micro plastics or a small spoon tipped with worm covers the summer program.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 10 to 30 ft | dawn | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 12 to 35 ft | midday | Jigging spoon (small), Perch rig / spreader |
| Winter | 15 to 35 ft | midday & dawn | Tungsten jig + spikes, Rattle spoon (small) |
Smallmouth Bass fishing at BIG THERRIAULT LAKE
In spring, smallmouth bass run shallow here, mostly 3 to 12 ft. They move out to 10 to 30 ft in summer and finish the year down in 20 to 45 ft. The spot to know is Main-lake point, a point in about 16 ft of water that rates prime for smallmouth bass in fall. In summer the feeding windows fall in early morning and the evening. Tie on a drop shot (goby/minnow) or a ned rig and you're in the game.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 3 to 12 ft | dawn & dusk | Ned rig, Tube jig |
| Summer | 10 to 30 ft | dawn & dusk | Drop shot (goby/minnow), Ned rig |
| Fall | 8 to 25 ft | midday & dawn | Jerkbait, Blade bait |
| Winter | 20 to 45 ft | midday | Blade bait, Hair jig |
Notable structure
- Deep basin: deep basin, around 79 ft
- Break off the point: drop-off, around 58 ft
- Main-lake point: point, around 16 ft
- Shallow bay flat: weed flat, around 7 ft
- Back-bay flat: weed flat, around 7 ft
Common questions
How deep is BIG THERRIAULT LAKE?
BIG THERRIAULT LAKE is about 80 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 BIG THERRIAULT LAKE?
Anglers target smallmouth bass, rainbow trout, yellow perch on BIG THERRIAULT LAKE.
Where is the best fishing spot on BIG THERRIAULT LAKE?
Shallow bay flat is the top-rated area: a weed flat in about 7 ft of water that rates prime for yellow perch in spring. Open the map above to see every rated spot for each species and season.
When is the best time to fish BIG THERRIAULT LAKE?
For rainbow 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
Little Therriault Lake · Glen Lake · Long Lake (Lincoln) · Rock Lake · Frank Lake · Martin Lake (Lincoln)
See how BIG THERRIAULT LAKE stacks up: best smallmouth bass lakes in Montana · best rainbow trout lakes in Montana · best yellow perch 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.