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789-acre lake in Thunder Bay District, Ontario. The lake tops out around 39 ft. The depth chart comes from Ontario Ministry of Natural Resources and Forestry bathymetric survey data, so the contours are survey-derived rather than computer-modeled. The depth data here comes from the Ontario MNRF survey of 1978, a decades-old survey (an MNRF lake survey). What follows comes from the same scoring engine that paints the spots above.
The drawn water covers 796 acres wrapped in 10.7 miles of bank, with 3 islands in the mix. The 2.7 development index tells the story — a convoluted bank whose fishable edge far outruns the acreage. Every acre of it sits shallower than ~15 ft: one big littoral zone, cover and forage throughout. Call it 1.7 mi long by 1.7 mi wide at the broadest reach. It sits in Thunder Bay District. Its nearest charted neighbour, Head Lake, is 3 mi to the east.
Start shallow in spring: lake whitefish sit in 12 to 39 ft that time of year. They don't go far with the seasons — 12 to 39 ft covers summer, 12 to 39 ft covers winter. The spot to know is Deep basin, a deep basin in about 30 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.
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 | 12 to 39 ft chart-limited; documented 15 to 45 ft | midday & dawn | Break off the point (6 ft) | Small jig + waxworm, Blade bait (small) |
| Summer | 12 to 39 ft chart-limited; documented 40 to 90 ft | dawn | Deep basin (30 ft) | Blade bait vertical, Small jigging spoon |
| Fall | 8 to 30 ft | dusk | Break off the point (6 ft) | Small spoon (gold), Jig + plastic larva |
| Winter | 12 to 39 ft chart-limited; documented 25 to 70 ft | midday & dawn | Deep basin (30 ft) | Jigging spoon + bead chain, Tungsten jig + waxie |
Start shallow in spring: cisco (lake herring) sit in 10 to 39 ft that time of year. They don't go far with the seasons — 12 to 39 ft covers summer, 12 to 39 ft covers winter. The spot to know is Deep basin, a deep basin in about 30 ft of water that rates prime for cisco (lake herring) in spring. 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.
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 39 ft chart-limited; documented 10 to 40 ft | dawn & dusk | Deep basin (30 ft) | Small silver spoon, Tiny swim jig (white) |
| Summer | 12 to 39 ft chart-limited; documented 40 to 80 ft | dawn | Deep basin (30 ft) | Vertical flutter spoon (small), Drop-shot micro plastic |
| Fall | 5 to 25 ft | dusk & dawn | Break off the point (6 ft) | Small casting spoon, Inline spinner (silver) |
| Winter | 12 to 39 ft chart-limited; documented 20 to 60 ft | dawn | Deep basin (30 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 12 to 39 ft for winter. Winter walleye concentrate at Deep basin, a prime-rated deep basin 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.
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 | 4 to 15 ft | dusk & dawn | Break off the point (6 ft) | 1/8 oz jig + minnow, Hair jig |
| Summer | 15 to 35 ft | dusk & dawn | Deep basin (30 ft) | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 12 to 39 ft chart-limited; documented 12 to 40 ft | dusk & night | Deep basin (30 ft) | Jigging rap, Jig + big minnow |
| Winter | 12 to 39 ft chart-limited; documented 20 to 40 ft | dusk & dawn | Deep basin (30 ft) | Jigging spoon + minnow head, Rattle bait |
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 Break off the point. It's a drop-off holding about 6 ft of water and rates prime come fall. 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 (1 ft) | #5 inline spinner, Spoon (red/white) |
| Summer | 8 to 20 ft | dawn & dusk | Break off the point (6 ft) | Bucktail, Weedless spoon over cabbage |
| Fall | 6 to 18 ft | midday & dawn | Break off the point (6 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Break off the point (6 ft) | Tip-ups, Large jigging spoon |
When the water first warms, smallmouth bass slide up into 3 to 12 ft. Summer is a 10 to 30 ft game here, winter a 12 to 39 ft one. Start at Break off the point. It's a drop-off holding about 6 ft of water and rates prime come fall. The feeding windows run early morning and the evening. Keep a drop shot (goby/minnow) or a ned rig 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 | 3 to 12 ft | dawn & dusk | Secondary point (2 ft) | Ned rig, Tube jig |
| Summer | 10 to 30 ft | dawn & dusk | Break off the point (6 ft) | Drop shot (goby/minnow), Ned rig |
| Fall | 8 to 25 ft | midday & dawn | Break off the point (6 ft) | Jerkbait, Blade bait |
| Winter | 12 to 39 ft chart-limited; documented 20 to 45 ft | midday | Break off the point (6 ft) | Blade bait, Hair jig |
6 pieces of structure are mapped here — Deep basin, around 30 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 Flatrock Lake specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
Flatrock Lake is about 39 ft (12 m) deep at its deepest point. The depth data here comes from the Ontario MNRF survey of 1978, a decades-old survey (an MNRF lake survey).
Anglers target lake whitefish, cisco (lake herring), walleye, northern pike, smallmouth bass on Flatrock Lake.
Deep basin is the top-rated area: a deep basin in about 30 ft of water that rates prime for lake whitefish in summer. 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 Flatrock 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.
Head Lake 3 mi · Kamikau Lake 4 mi · Sandstone Lake 5 mi · Atik Lake 6 mi · Weikwabinonaw Lake 6 mi · Roundtable Lake 7 mi · McGrath Lake 8 mi · Amethyst Lake 8 mi · Arrow Lake (North East) 8 mi · Chambers Lake 9 mi · Scott Lake 9 mi · Blunder Lake 9 mi
See how Flatrock Lake stacks up: best smallmouth bass lakes in Ontario · best walleye lakes in Ontario · best northern pike 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. Bathymetry: published agency survey data. 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.