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488-acre lake in Sudbury District, Ontario. The lake tops out around 120 ft. The depth data here comes from a transect sounding survey by the Ontario MNRF. Here's the year, species by species, as the scoring engine sees it.
On the chart, Great Mountain Lake draws 490 acres inside 11.3 miles of shoreline — 7 islands included. The 3.6 development index tells the story — a convoluted bank whose fishable edge far outruns the acreage. Roughly 30% of the water is 15 ft or less, the band where the food chain lives. The basin spans about 1.9 mi end to end and 1.4 mi across at its widest. You'll find it in Sudbury District. Closest neighbour on DepthScout: Little Mountain Lake, 1 mi south of here.
The spring pattern is a shallow one: lake trout in 10 to 40 ft. Midsummer fish sit out in 50 to 120 ft before dropping to 20 to 80 ft for winter. The spot to know is Deep basin, a deep basin in about 120 ft of water that rates prime for lake trout in summer. Plan around early morning in the warm months. 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 (20 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 (20 ft) | Heavy casting spoon, Jigging rap over reefs |
| Winter | 20 to 80 ft | dawn | Break off the point (52 ft) | White tube jig, Airplane jig |
Come spring, look for cisco (lake herring) tight to the bank in 10 to 40 ft. They move out to 40 to 80 ft in summer and finish the year down in 20 to 60 ft. If you only fish one area, make it Break off the point: a drop-off around 52 ft that scores prime in winter. Best bite is early morning. A vertical flutter spoon (small) or a drop-shot micro plastic is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 10 to 40 ft | dawn & dusk | Deep basin (120 ft) | Small silver spoon, Tiny swim jig (white) |
| Summer | 40 to 80 ft | dawn | Break off the point (52 ft) | Vertical flutter spoon (small), Drop-shot micro plastic |
| Fall | 5 to 25 ft | dusk & dawn | open water | Small casting spoon, Inline spinner (silver) |
| Winter | 20 to 60 ft | dawn | Break off the point (52 ft) | Small jigging spoon (glow/silver), Tungsten jig + minnow head |
In spring, smallmouth bass run shallow here, mostly 3 to 12 ft. Midsummer fish sit out in 10 to 30 ft before dropping to 20 to 45 ft for winter. Fall smallmouth bass concentrate at Main-lake point, a prime-rated point around 20 ft. Fish it in early morning and the evening and you'll meet the bite. 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 | Secondary point (1 ft) | Ned rig, Tube jig |
| Summer | 10 to 30 ft | dawn & dusk | Main-lake point (20 ft) | Drop shot (goby/minnow), Ned rig |
| Fall | 8 to 25 ft | midday & dawn | Main-lake point (20 ft) | Jerkbait, Blade bait |
| Winter | 20 to 45 ft | midday | Break off the point (52 ft) | Blade bait, Hair jig |
Come spring, look for rock bass tight to the bank in 2 to 10 ft. They move out to 5 to 20 ft in summer and finish the year down in 12 to 30 ft. If you only fish one area, make it Main-lake point: a point around 20 ft that scores prime in summer. Best bite is the evening. A ned rig (small) or a marabou jig is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 10 ft | midday & dawn | Secondary point (1 ft) | 1/16 oz jig + grub, Small inline spinner |
| Summer | 5 to 20 ft | dusk | Main-lake point (20 ft) | Ned rig (small), Marabou jig |
| Fall | 8 to 22 ft | midday | Main-lake point (20 ft) | Small tube jig, Inline spinner |
| Winter | 12 to 30 ft | midday | Deep basin (120 ft) | Tungsten jig + plastic, Small spoon + spike |
Come spring, look for pumpkinseed tight to the bank in 1 to 8 ft. They move out to 2 to 10 ft in summer and finish the year down in 6 to 18 ft. If you only fish one area, make it Shallow bay flat: a weed flat around 1 ft that scores prime in spring. Best bite is the evening and early morning. A micro tube or a sponge spider (fly) is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 1 to 8 ft | midday & dusk | Shallow bay flat (1 ft) | Micro jig under a float, Tiny beetle-spin |
| Summer | 2 to 10 ft | dusk & dawn | Shallow bay flat (1 ft) | Micro tube, Sponge spider (fly) |
| Fall | 4 to 14 ft | dusk & dawn | Shallow bay flat (1 ft) | Micro jig + waxworm, Small spoon tipped |
| Winter | 6 to 18 ft | dawn | Shallow bay flat (1 ft) | Tungsten ice jig + plastic, Tiny spoon |
6 pieces of structure are mapped here — Deep basin, around 120 ft, is the deepest of them.
Season dates, license requirements, and size and bag limits for Ontario waters are set by the Ontario fishing regulations (FMZ summary) — and special regulations can apply to Great Mountain Lake specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
Great Mountain Lake is about 120 ft (37 m) deep at its deepest point. The depth data here comes from a transect sounding survey by the Ontario MNRF.
Anglers target lake trout, cisco (lake herring), smallmouth bass, rock bass, pumpkinseed on Great Mountain Lake.
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 lake trout, the summer bite is best in 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 Great Mountain Lake is regulated by the Ontario fishing regulations (FMZ summary). Check the official Ontario regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.
Little Mountain Lake 1 mi · Gail Lake 1 mi · Fish Lake 2 mi · Boundary Lake 3 mi · Harry Lake 3 mi · David Lake 4 mi · Gem Lake 4 mi · Cat Lake 4 mi · Balsam Lake 5 mi · Bear Lake 5 mi · Howry Lake 5 mi · Sandy Lake 5 mi
See how Great Mountain Lake stacks up: best smallmouth bass lakes in Ontario · best lake trout lakes in Ontario · best rock bass lakes in Ontario · best cisco (lake herring) lakes in Ontario
More water nearby: Sudbury District fishing maps (868 charts). Browse all Ontario fishing maps or see every water on DepthScout. Bathymetry credit: state fisheries survey programs. 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.