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Rating depth structure for brook trout.
Recent public catches load as you reach this section.
240-acre lake in Thunder Bay District, Ontario. The lake tops out around 144 ft. Bathymetry on this water is estimated from its real outline and maximum depth. Use it to shortlist water, then verify with your electronics — and never navigate by it. What follows comes from the same scoring engine that paints the spots above.
The drawn water covers 243 acres wrapped in 8.3 miles of bank, broken up by 2 islands. With a shoreline index of 3.8, this water is all arms and coves — edge habitat well beyond its acreage. Roughly 60% of the water is 15 ft or less as modeled, the band where the food chain lives. The basin spans about 2.1 mi end to end and 0.7 mi across at its widest. Thunder Bay District claims this one. Bluebill Lake sits 3 mi southwest — the closest neighbouring chart.
When the water first warms, brook trout slide up into 2 to 15 ft. Summer is a 10 to 30 ft game here, winter a 3 to 20 ft one. Start at Shallow bay flat. It's a weed flat holding about 6 ft of water and rates good come spring. The feeding windows run early morning and the evening. Keep a small spoon fished deep or a trolled lake-clear wobbler + worm rigged through the warm months.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 15 ft | dawn & dusk | Shallow bay flat (6 ft) | Small inline spinner (gold), Tiny spoon |
| Summer | 10 to 30 ft | dawn & dusk | open water | Small spoon fished deep, Trolled lake-clear wobbler + worm |
| Fall | 2 to 15 ft | midday & dawn | open water | Small spoon (orange), Spinner |
| Winter | 3 to 20 ft | dawn | Shallow bay flat (6 ft) | Small jigging spoon, Tungsten jig + plastic |
Count 6 structure marks on this chart. The deepest, Deep basin, sits near 122 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 Ault Lake specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
Ault Lake is about 144 ft (44 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 brook trout on Ault Lake.
Shallow bay flat is the top-rated area: a weed flat in about 6 ft of water that rates good for brook trout in spring. Open the map above to see every rated spot for each species and season.
For brook trout, the summer bite is best in early morning and the evening. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.
Fishing on Ault 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.
Bluebill Lake 3 mi · Cavers Lake 4 mi · Buckaday Lake 6 mi · Gurney Lake 11 mi · Antler Lake 11 mi · Ambrose Lake 12 mi · Devious Lake 15 mi · Flicker Lake 16 mi · Big Duck Lake 16 mi · Chapman Lake 16 mi · Bluff Lake 17 mi · Deep Lake 17 mi
See how Ault Lake stacks up: best brook 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.