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Rating depth structure for lake trout.
Recent public catches load as you reach this section.
1,479-acre lake in Thunder Bay District, Ontario. The lake tops out around 110 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. The season-by-season read for each species follows, from the map's own numbers.
The drawn water covers 1,479 acres wrapped in 15.6 miles of bank — 2 islands included. The 2.9 development index tells the story — a convoluted bank whose fishable edge far outruns the acreage. Littoral water — the productive band under ~15 ft — makes up 29% of this chart, as modeled. Call it 3.3 mi long by 2.2 mi wide at the broadest reach. It sits in Thunder Bay District. Its nearest charted neighbour, Kilgour Lake, is 2 mi to the east.
When the water first warms, lake trout slide up into 10 to 40 ft. By summer they slide out to 33 to 110 ft, and by winter most fish are in 20 to 80 ft. If you only fish one area, make it Deep basin: a deep basin around 94 ft that scores prime in summer. In summer the feeding windows fall in early morning. Keep a white tube jig (deep) or a magnum spoon on downrigger rigged through the warm months.
Depth note: when a documented seasonal range extends below this chart, the table shows the deepest mapped working water, not a verified holding depth.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 10 to 40 ft | dawn & dusk | Main-lake point (28 ft) | Casting spoon over shoals, Jerkbait (shallow) |
| Summer | 33 to 110 ft chart-limited; documented 50 to 120 ft | dawn | Deep basin (94 ft) | White tube jig (deep), Magnum spoon on downrigger |
| Fall | 10 to 50 ft | dusk & dawn | Main-lake point (28 ft) | Heavy casting spoon, Jigging rap over reefs |
| Winter | 20 to 80 ft | dawn | Break off the point (50 ft) | White tube jig, Airplane jig |
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 Deep basin, a deep basin in about 94 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 (50 ft) | Small jig + waxworm, Blade bait (small) |
| Summer | 40 to 90 ft | dawn | Deep basin (94 ft) | Blade bait vertical, Small jigging spoon |
| Fall | 8 to 30 ft | dusk | Main-lake point (28 ft) | Small spoon (gold), Jig + plastic larva |
| Winter | 25 to 70 ft | midday & dawn | Break off the point (50 ft) | Jigging spoon + bead chain, Tungsten jig + waxie |
6 pieces of structure are mapped here — Deep basin, around 94 ft, is the deepest of them.
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 Cosgrave Lake specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
Cosgrave Lake is about 110 ft (34 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 on Cosgrave Lake.
Deep basin is the top-rated area: a deep basin in about 94 ft of water that rates prime for lake trout in summer. The interactive chart above rates every 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 Cosgrave 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.
Kilgour Lake 2 mi · Georgia Lake 7 mi · Gorge Lake 7 mi · Keemle Lake 9 mi · Devious Lake 9 mi · Shamrock Lake 9 mi · McKirdy Lake 9 mi · Barbara Lake 9 mi · Lake Jean 11 mi · Postagoni Lake 12 mi · Gurney Lake 13 mi · Parland Lake 13 mi
See how Cosgrave Lake stacks up: best lake trout lakes in Ontario · best lake whitefish 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.