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10,365-acre lake in Thunder Bay District, Ontario. The lake tops out around 150 ft. This chart interpolates between a real shoreline and a known maximum depth. It will point you at likely water, but it is not a navigation product. What the data behind the map says about each species, season by season:
O'Sullivan Lake maps at 10,413 acres behind 119 miles of shoreline — 49 islands included. With a shoreline index of 8.3, this water is all arms and coves — edge habitat well beyond its acreage. About 54% of the surface sits shallower than 15 ft on the modeled chart — that's the weed-and-bait zone. The basin spans about 7.6 mi end to end and 6 mi across at its widest. It sits in Thunder Bay District. If the bite dies, Hanover Lake is 6 mi to the southwest.
Come spring, look for lake trout tight to the bank in 10 to 40 ft. Expect a summer slide to 50 to 120 ft, then a winter hold in 20 to 80 ft. Start at Rock reef. It's a rock pile holding about 8 ft of water and rates prime come fall. Prime time lands in early morning. A white tube jig (deep) or a magnum spoon on downrigger is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 10 to 40 ft | dawn & dusk | Main-lake point (38 ft) | Casting spoon over shoals, Jerkbait (shallow) |
| Summer | 50 to 120 ft | dawn | Deep basin (128 ft) | White tube jig (deep), Magnum spoon on downrigger |
| Fall | 10 to 50 ft | dusk & dawn | Rock reef (8 ft) | Heavy casting spoon, Jigging rap over reefs |
| Winter | 20 to 80 ft | dawn | Break off the point (68 ft) | White tube jig, Airplane jig |
The spring pattern is a shallow one: lake whitefish in 15 to 45 ft. As the season builds they drop to 40 to 90 ft, wintering in 25 to 70 ft. Top water on the chart: Rock reef, a rock pile in the 8 ft range, prime in fall. Time it for early morning. Summer baits: a blade bait vertical or a small jigging spoon gets it done.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 15 to 45 ft | midday & dawn | Offshore hump (15 ft) | Small jig + waxworm, Blade bait (small) |
| Summer | 40 to 90 ft | dawn | Break off the point (68 ft) | Blade bait vertical, Small jigging spoon |
| Fall | 8 to 30 ft | dusk | Rock reef (8 ft) | Small spoon (gold), Jig + plastic larva |
| Winter | 25 to 70 ft | midday & dawn | Break off the point (68 ft) | Jigging spoon + bead chain, Tungsten jig + waxie |
The spring pattern is a shallow one: cisco (lake herring) in 10 to 40 ft. As the season builds they drop to 40 to 80 ft, wintering in 20 to 60 ft. Top water on the chart: Rock reef, a rock pile in the 8 ft range, prime in fall. Time it for early morning. Summer baits: a vertical flutter spoon (small) or a drop-shot micro plastic gets it done.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 10 to 40 ft | dawn & dusk | Offshore hump (15 ft) | Small silver spoon, Tiny swim jig (white) |
| Summer | 40 to 80 ft | dawn | Break off the point (68 ft) | Vertical flutter spoon (small), Drop-shot micro plastic |
| Fall | 5 to 25 ft | dusk & dawn | Rock reef (8 ft) | Small casting spoon, Inline spinner (silver) |
| Winter | 20 to 60 ft | dawn | Offshore hump (15 ft) | Small jigging spoon (glow/silver), Tungsten jig + minnow head |
Spring puts walleye in skinny water — 4 to 15 ft is the zone. Warm water sends them out to 15 to 35 ft; cold water stacks them in 20 to 40 ft. Offshore hump is the standout, an offshore hump at roughly 15 ft, rated prime for summer walleye. Plan around the evening and early morning in the warm months. A crawler harness on bottom bouncer or a deep crankbait (trolled) covers the summer program.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 4 to 15 ft | dusk & dawn | Rock reef (8 ft) | 1/8 oz jig + minnow, Hair jig |
| Summer | 15 to 35 ft | dusk & dawn | Offshore hump (15 ft) | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 12 to 40 ft | dusk & night | Sharp break (35 ft) | Jigging rap, Jig + big minnow |
| Winter | 20 to 40 ft | dusk & dawn | Sharp break (35 ft) | Jigging spoon + minnow head, Rattle bait |
Start shallow in spring: yellow perch sit in 3 to 12 ft that time of year. Warm water sends them out to 10 to 30 ft; cold water stacks them in 15 to 35 ft. Top water on the chart: Shallow bay flat, a weed flat in the 6 ft range, prime in spring. Fish it in early morning and you'll meet the bite. Throw a drop-shot micro plastics or a small spoon tipped with worm until the fish tell you otherwise.
| 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 | Offshore hump (15 ft) | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 12 to 35 ft | midday | Sharp break (35 ft) | Jigging spoon (small), Perch rig / spreader |
| Winter | 15 to 35 ft | midday & dawn | Offshore hump (15 ft) | Tungsten jig + spikes, Rattle spoon (small) |
Come spring, look for northern pike tight to the bank in 2 to 8 ft. They move out to 8 to 20 ft in summer and finish the year down in 5 to 15 ft. If you only fish one area, make it Shallow bay flat: a weed flat around 6 ft that scores prime in spring. Best bite is early morning and the evening. A bucktail or a weedless spoon over cabbage is the honest summer answer here.
| 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 |
O'Sullivan Lake also holds burbot (50 to 120 ft in summer). Pick any of them on the map above for rated spots and bait picks.
Structure-wise the chart holds 12 features, led in depth by Deep basin at roughly 128 ft.
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 O'Sullivan Lake specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
O'Sullivan Lake is about 150 ft (46 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 trout, lake whitefish, cisco (lake herring), walleye, yellow perch, northern pike, burbot on O'Sullivan Lake.
Rock reef is the top-rated area: a rock pile in about 8 ft of water that rates prime for lake whitefish in fall. Every other rated spot, per species and season, is on the map above.
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 O'Sullivan 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.
Hanover Lake 6 mi · Boston Lake 7 mi · Lucy Lake 10 mi · Esnagami Lake 11 mi · Clover Lake 15 mi · Meta Lake 15 mi · Betty Lake 15 mi · Brace Lake 16 mi · Durer Lake 17 mi · Trident Lake 18 mi · Alph Lake 19 mi · Melchett Lake 19 mi
See how O'Sullivan Lake stacks up: best walleye lakes in Ontario · best northern pike lakes in Ontario · best yellow perch lakes in Ontario · best lake trout lakes in Ontario
More water nearby: Thunder Bay District fishing maps (662 charts). Browse all Ontario fishing maps. 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.