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327-acre lake in Sudbury District, Ontario. The lake tops out around 120 ft. Depth here is modeled from the true shoreline and max depth rather than surveyed; use it to plan, not to navigate. The season-by-season read for each species follows, from the map's own numbers.
Upper Grassy Lake maps at 325 acres behind 7.8 miles of shoreline. That shoreline is heavily fingered (development index 3.1) — bays, points and pockets everywhere, which multiplies the fishable edge. The shallow band under 15 ft claims about 31% of the surface on the model — that's where the groceries are. End to end it runs roughly 3.2 mi, about 0.4 mi across. It sits in Sudbury District. If the bite dies, Mond Lake is 4 mi to the northeast.
Start shallow in spring: lake whitefish sit in 15 to 45 ft that time of year. Summer pushes them deeper, 40 to 90 ft, and winter fish settle into 25 to 70 ft. The spot to know is Break off the point, a drop-off in about 54 ft of water that rates prime for lake whitefish in summer. Warm-month bites cluster around early morning. Throw a blade bait vertical or a small jigging spoon until the fish tell you otherwise.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 15 to 45 ft | midday & dawn | Break off the point (54 ft) | Small jig + waxworm, Blade bait (small) |
| Summer | 40 to 90 ft | dawn | Break off the point (54 ft) | Blade bait vertical, Small jigging spoon |
| Fall | 8 to 30 ft | dusk | Main-lake point (30 ft) | Small spoon (gold), Jig + plastic larva |
| Winter | 25 to 70 ft | midday & dawn | Break off the point (54 ft) | Jigging spoon + bead chain, Tungsten jig + waxie |
Start shallow in spring: cisco (lake herring) sit in 10 to 40 ft that time of year. Summer pushes them deeper, 40 to 80 ft, and winter fish settle into 20 to 60 ft. The spot to know is Break off the point, a drop-off in about 54 ft of water that rates prime for cisco (lake herring) in winter. Warm-month bites cluster around early morning. Throw a vertical flutter spoon (small) or a drop-shot micro plastic until the fish tell you otherwise.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 10 to 40 ft | dawn & dusk | Deep basin (102 ft) | Small silver spoon, Tiny swim jig (white) |
| Summer | 40 to 80 ft | dawn | Break off the point (54 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 (54 ft) | Small jigging spoon (glow/silver), Tungsten jig + minnow head |
In spring, walleye run shallow here, mostly 4 to 15 ft. Midsummer fish sit out in 15 to 35 ft before dropping to 20 to 40 ft for winter. Fall walleye concentrate at Main-lake point, a prime-rated point around 30 ft. Fish it in the evening and early morning and you'll meet the bite. You won't need more than a crawler harness on bottom bouncer or a deep crankbait (trolled) most summer days.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 4 to 15 ft | dusk & dawn | open water | 1/8 oz jig + minnow, Hair jig |
| Summer | 15 to 35 ft | dusk & dawn | Main-lake point (30 ft) | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 12 to 40 ft | dusk & night | Main-lake point (30 ft) | Jigging rap, Jig + big minnow |
| Winter | 20 to 40 ft | dusk & dawn | Main-lake point (30 ft) | Jigging spoon + minnow head, Rattle bait |
The spring pattern is a shallow one: yellow perch in 3 to 12 ft. Midsummer fish sit out in 10 to 30 ft before dropping to 15 to 35 ft for winter. The spot to know is Shallow bay flat, a weed flat in about 6 ft of water that rates prime for yellow perch in spring. Plan around early morning in the warm months. Summer baits: a drop-shot micro plastics or a small spoon tipped with worm gets it done.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Shallow bay flat (6 ft) | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 10 to 30 ft | dawn | Shallow bay flat (6 ft) | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 12 to 35 ft | midday | Deep basin (102 ft) | Jigging spoon (small), Perch rig / spreader |
| Winter | 15 to 35 ft | midday & dawn | Deep basin (102 ft) | Tungsten jig + spikes, Rattle spoon (small) |
When the water first warms, northern pike slide up into 2 to 8 ft. Summer is an 8 to 20 ft game here, winter a 5 to 15 ft one. Start at Shallow bay flat. It's a weed flat holding about 6 ft of water and rates prime come spring. The feeding windows run early morning and the evening. Keep a bucktail or a weedless spoon over cabbage rigged through the warm months.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | Shallow bay flat (6 ft) | #5 inline spinner, Spoon (red/white) |
| Summer | 8 to 20 ft | dawn & dusk | Shallow bay flat (6 ft) | Bucktail, Weedless spoon over cabbage |
| Fall | 6 to 18 ft | midday & dawn | Shallow bay flat (6 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Shallow bay flat (6 ft) | Tip-ups, Large jigging spoon |
Structure-wise the chart holds 6 features, led in depth by Deep basin at roughly 102 ft.
Access data: Geospatial Ontario - Fishing Access Points. Confirm conditions and fees locally before you launch.
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 Upper Grassy Lake specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
Upper Grassy Lake is about 120 ft (37 m) deep at its deepest point. The contours here are modeled from the water's real shape and maximum depth, so treat them as a rough guide.
Anglers target lake whitefish, cisco (lake herring), walleye, yellow perch, northern pike on Upper Grassy Lake.
Shallow bay flat is the top-rated area: a weed flat in about 6 ft of water that rates prime for yellow perch in spring. The interactive chart above rates every spot for each species and season.
For lake whitefish, 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 Upper Grassy 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.
Mond Lake 4 mi · Marne Lake 5 mi · Scotties L. 6 mi · Cabot Lake 7 mi · Caribou Lake 7 mi · Nissin L. 7 mi · Bigfour Lake 7 mi · Ferris Lake 7 mi · Kwitosse Lake 8 mi · Burrows L. 5 8 mi · Claw Lake 8 mi · Robbie Lake 8 mi
See how Upper Grassy Lake stacks up: best walleye lakes in Ontario · best northern pike lakes in Ontario · best yellow perch lakes in Ontario · best lake whitefish lakes in Ontario
More water nearby: Sudbury District fishing maps (868 charts). Browse all Ontario fishing maps or see every water on DepthScout. 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.