Sign inSign up free Sign inSign up free Sign inSign up freeLake depth chart
Today's read
Recent public catches load as you reach this section.
5,914-acre lake in Thunder Bay District, Ontario. The lake tops out around 66 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 1980 (a transect sounding survey). Here is how the season plays out for each species, straight from the data behind the map.
Brennan Lake maps at 5,942 acres behind 152.3 miles of shoreline — 193 islands included. With a shoreline index of 14.1, this water is all arms and coves — edge habitat well beyond its acreage. Roughly 90% of the water is 15 ft or less, the band where the food chain lives. The basin spans about 12.2 mi end to end and 5.1 mi across at its widest. It sits in Thunder Bay District. Its nearest charted neighbour, Change Lake, is 4 mi to the south.
In spring, lake whitefish run shallow here, mostly 15 to 45 ft. Summer pushes them deeper, 20 to 66 ft, and winter fish settle into 20 to 66 ft. Deep basin is the standout, a deep basin at roughly 45 ft, rated prime for summer lake whitefish. Time it for early morning. You won't need more than a blade bait vertical or a small jigging spoon 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 | 15 to 45 ft | midday & dawn | Sharp break (17 ft) | Small jig + waxworm, Blade bait (small) |
| Summer | 20 to 66 ft chart-limited; documented 40 to 90 ft | dawn | Deep basin (45 ft) | Blade bait vertical, Small jigging spoon |
| Fall | 8 to 30 ft | dusk | Rock reef (3 ft) | Small spoon (gold), Jig + plastic larva |
| Winter | 20 to 66 ft chart-limited; documented 25 to 70 ft | midday & dawn | Deep basin (45 ft) | Jigging spoon + bead chain, Tungsten jig + waxie |
In spring, cisco (lake herring) run shallow here, mostly 10 to 40 ft. Summer pushes them deeper, 20 to 66 ft, and winter fish settle into 20 to 60 ft. Deep basin is the standout, a deep basin at roughly 45 ft, rated prime for summer cisco (lake herring). Time it for early morning. You won't need more than a vertical flutter spoon (small) or a drop-shot micro plastic 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 | 10 to 40 ft | dawn & dusk | Deep basin (45 ft) | Small silver spoon, Tiny swim jig (white) |
| Summer | 20 to 66 ft chart-limited; documented 40 to 80 ft | dawn | Deep basin (45 ft) | Vertical flutter spoon (small), Drop-shot micro plastic |
| Fall | 5 to 25 ft | dusk & dawn | Rock reef (3 ft) | Small casting spoon, Inline spinner (silver) |
| Winter | 20 to 60 ft | dawn | Deep basin (45 ft) | Small jigging spoon (glow/silver), Tungsten jig + minnow head |
The spring pattern is a shallow one: walleye in 4 to 15 ft. Midsummer fish sit out in 15 to 35 ft before dropping to 20 to 40 ft for winter. The spot to know is Sharp break, a drop-off in about 17 ft of water that rates prime for walleye in fall. Plan around the evening and early morning in the warm months. Summer baits: a crawler harness on bottom bouncer or a deep crankbait (trolled) gets it done.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 4 to 15 ft | dusk & dawn | Rock reef (3 ft) | 1/8 oz jig + minnow, Hair jig |
| Summer | 15 to 35 ft | dusk & dawn | Sharp break (17 ft) | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 12 to 40 ft | dusk & night | Sharp break (17 ft) | Jigging rap, Jig + big minnow |
| Winter | 20 to 40 ft | dusk & dawn | Deep basin (45 ft) | Jigging spoon + minnow head, Rattle bait |
In spring, yellow perch run shallow here, mostly 3 to 12 ft. Midsummer fish sit out in 10 to 30 ft before dropping to 15 to 35 ft for winter. Summer yellow perch concentrate at Sharp break, a prime-rated drop-off around 10 ft. Fish it in early morning and you'll meet the bite. You won't need more than a drop-shot micro plastics or a small spoon tipped with worm most summer days.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Shallow bay flat (2 ft) | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 10 to 30 ft | dawn | Sharp break (10 ft) | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 12 to 35 ft | midday | Sharp break (17 ft) | Jigging spoon (small), Perch rig / spreader |
| Winter | 15 to 35 ft | midday & dawn | Sharp break (17 ft) | Tungsten jig + spikes, Rattle spoon (small) |
Early season northern pike use the shallows, holding in 2 to 8 ft. Summer is an 8 to 20 ft game here, winter a 5 to 15 ft one. The chart's best answer is Shallow bay flat — weed flat, 2 ft, prime for spring. Best bite is early morning and the evening. Tie on a bucktail or a weedless spoon over cabbage and you're in the game.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | Shallow bay flat (2 ft) | #5 inline spinner, Spoon (red/white) |
| Summer | 8 to 20 ft | dawn & dusk | Sharp break (10 ft) | Bucktail, Weedless spoon over cabbage |
| Fall | 6 to 18 ft | midday & dawn | Sharp break (10 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Shallow feeding flat (15 ft) | Tip-ups, Large jigging spoon |
Spring burbot on Brennan Lake hold shallow, usually 20 to 66 ft. Depth-wise the year is flat: 20 to 66 ft in summer, 15 to 60 ft once it turns cold. The chart's best answer is Deep basin — deep basin, 45 ft, prime for spring. Prime time lands in after dark and midday. The summer box starts with a heavy jig + cut bait.
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 | 20 to 66 ft chart-limited; documented 25 to 70 ft | night & dusk | Deep basin (45 ft) | Glow jigging spoon + cut bait, Rattle bait (dark) |
| Summer | 20 to 66 ft chart-limited; documented 50 to 120 ft | night & midday | Deep basin (45 ft) | Heavy jig + cut bait |
| Fall | 20 to 66 ft chart-limited; documented 30 to 80 ft | night & dusk | Deep basin (45 ft) | Glow spoon + minnow head, Blade bait (slow) |
| Winter | 15 to 60 ft | night & dusk | Deep basin (45 ft) | Glow tungsten + cut bait, Rattle spoon + minnow head |
Count 15 structure marks on this chart. The deepest, Deep basin, sits near 45 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 Brennan Lake specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
Brennan Lake is about 66 ft (20 m) deep at its deepest point. The depth data here comes from the Ontario MNRF survey of 1980 (a transect sounding survey).
Anglers target lake whitefish, cisco (lake herring), walleye, yellow perch, northern pike, burbot on Brennan Lake. This isn't a survey of the lake — none is on record for it — but an informed estimate from the species Ontario's MNRF recorded in the nearest surveyed lakes, filtered to this lake's depth and habitat.
Deep basin is the top-rated area: a deep basin in about 45 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 Brennan 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.
Change Lake 4 mi · Dagger Lake 5 mi · Granite Lake 8 mi · McWade Lake 11 mi · Berry Lake 13 mi · Sassenach Lake 14 mi · Redhead Lake 14 mi · Hillside Lake 15 mi · Painter L. 15 mi · Elga L. 16 mi · Ranger Lake 16 mi · Surprise Lake 18 mi
See how Brennan 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: 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.