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.
2,648-acre lake in Rainy River District, Ontario. The lake tops out around 30 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 rest of this page walks each species through its year, using the map's own scoring.
Traced from the shoreline, Mainville Lake runs 2,659 acres with 46.2 miles of edge, with 7 islands in the mix. An index of 6.4 puts the bank firmly in maze territory: point after pocket after cove, every one a casting target. About 97% of the surface sits shallower than 15 ft — that's the weed-and-bait zone. Tip to tip the water measures near 7.6 mi with a 2.6-mi widest point. You'll find it in Rainy River District. For a second option, Obikoba Lake lies 3 mi southeast.
Spring lake whitefish on Mainville Lake hold shallow, usually 9 to 30 ft. Depth-wise the year is flat: 9 to 30 ft in summer, 9 to 30 ft once it turns cold. Put Deep basin first on the milk run — a deep basin near 29 ft that grades prime for summer. The feeding windows run early morning. The summer box starts with a blade bait vertical or a small jigging spoon.
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 | 9 to 30 ft chart-limited; documented 15 to 45 ft | midday & dawn | Shallow feeding flat (18 ft) | Small jig + waxworm, Blade bait (small) |
| Summer | 9 to 30 ft chart-limited; documented 40 to 90 ft | dawn | Deep basin (29 ft) | Blade bait vertical, Small jigging spoon |
| Fall | 8 to 30 ft | dusk | Sharp break (5 ft) | Small spoon (gold), Jig + plastic larva |
| Winter | 9 to 30 ft chart-limited; documented 25 to 70 ft | midday & dawn | Deep basin (29 ft) | Jigging spoon + bead chain, Tungsten jig + waxie |
Spring cisco (lake herring) on Mainville Lake hold shallow, usually 8 to 30 ft. Depth-wise the year is flat: 9 to 30 ft in summer, 9 to 30 ft once it turns cold. Put Deep basin first on the milk run — a deep basin near 29 ft that grades prime for spring. The feeding windows run early morning. The summer box starts with a vertical flutter spoon (small) or a drop-shot micro plastic.
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 | 8 to 30 ft chart-limited; documented 10 to 40 ft | dawn & dusk | Deep basin (29 ft) | Small silver spoon, Tiny swim jig (white) |
| Summer | 9 to 30 ft chart-limited; documented 40 to 80 ft | dawn | Deep basin (29 ft) | Vertical flutter spoon (small), Drop-shot micro plastic |
| Fall | 5 to 25 ft | dusk & dawn | Sharp break (5 ft) | Small casting spoon, Inline spinner (silver) |
| Winter | 9 to 30 ft chart-limited; documented 20 to 60 ft | dawn | Deep basin (29 ft) | Small jigging spoon (glow/silver), Tungsten jig + minnow head |
When the water first warms, walleye slide up into 4 to 15 ft. By summer they slide out to 9 to 30 ft, and by winter most fish are in 9 to 30 ft. If you only fish one area, make it Deep basin: a deep basin around 29 ft that scores prime in winter. In summer the feeding windows fall in the evening and early morning. Keep a crawler harness on bottom bouncer or a deep crankbait (trolled) 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 | 4 to 15 ft | dusk & dawn | Shoreline point (4 ft) | 1/8 oz jig + minnow, Hair jig |
| Summer | 9 to 30 ft chart-limited; documented 15 to 35 ft | dusk & dawn | Deep basin (29 ft) | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 9 to 30 ft chart-limited; documented 12 to 40 ft | dusk & night | Deep basin (29 ft) | Jigging rap, Jig + big minnow |
| Winter | 9 to 30 ft chart-limited; documented 20 to 40 ft | dusk & dawn | Deep basin (29 ft) | Jigging spoon + minnow head, Rattle bait |
When the water first warms, yellow perch slide up into 3 to 12 ft. Summer is a 10 to 30 ft game here, winter a 9 to 30 ft one. Start at Deep basin. It's a deep basin holding about 29 ft of water and rates prime come fall. The feeding windows run early morning. Keep a drop-shot micro plastics or a small spoon tipped with worm 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 | midday & dawn | Shallow bay flat (1 ft) | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 10 to 30 ft | dawn | Deep basin (29 ft) | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 9 to 30 ft chart-limited; documented 12 to 35 ft | midday | Deep basin (29 ft) | Jigging spoon (small), Perch rig / spreader |
| Winter | 9 to 30 ft chart-limited; documented 15 to 35 ft | midday & dawn | Deep basin (29 ft) | Tungsten jig + spikes, Rattle spoon (small) |
The spring pattern is a shallow one: northern pike in 2 to 8 ft. Midsummer fish sit out in 8 to 20 ft before dropping to 5 to 15 ft for winter. The spot to know is Shallow bay flat, a weed flat in about 1 ft of water that rates prime for northern pike in spring. Plan around early morning and the evening in the warm months. Summer baits: a bucktail or a weedless spoon over cabbage gets it done.
| 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 | Shallow feeding flat (18 ft) | Bucktail, Weedless spoon over cabbage |
| Fall | 6 to 18 ft | midday & dawn | Sharp break (5 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Sharp break (5 ft) | Tip-ups, Large jigging spoon |
The spring pattern is a shallow one: smallmouth bass in 3 to 12 ft. Midsummer fish sit out in 10 to 30 ft before dropping to 9 to 30 ft for winter. The spot to know is Shoreline point, a point in about 4 ft of water that rates prime for smallmouth bass in spring. Plan around early morning and the evening in the warm months. Summer baits: a drop shot (goby/minnow) or a ned rig gets it done.
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 | Shoreline point (4 ft) | Ned rig, Tube jig |
| Summer | 10 to 30 ft | dawn & dusk | Sharp break (5 ft) | Drop shot (goby/minnow), Ned rig |
| Fall | 8 to 25 ft | midday & dawn | Shoreline point (4 ft) | Jerkbait, Blade bait |
| Winter | 9 to 30 ft chart-limited; documented 20 to 45 ft | midday | Sharp break (5 ft) | Blade bait, Hair jig |
Mainville Lake also holds rock bass (5 to 20 ft in summer). Pick any of them on the map above for rated spots and bait picks.
The chart marks 10 structure features on Mainville Lake; the deepest is Deep basin at about 29 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 Mainville Lake specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
Mainville Lake is about 30 ft (9 m) deep at its deepest point. 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.
Anglers target lake whitefish, cisco (lake herring), walleye, yellow perch, northern pike, smallmouth bass, rock bass on Mainville Lake.
Deep basin is the top-rated area: a deep basin in about 29 ft of water that rates prime for lake whitefish in summer. The map above holds the full rated-spot list for every 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 Mainville 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.
Obikoba Lake 3 mi · Cuttle Lake 4 mi · Hickerson Lake 7 mi · Weller Lake 7 mi · Poulson Lake 7 mi · Strong Lake 7 mi · Tupman Lake 8 mi · Rainy Lake 9 mi, MN · Big Sawbill Lake 10 mi · Rainy Lake 10 mi · Grimshaw Lake 10 mi · Sphene Lake 11 mi
See how Mainville Lake stacks up: best smallmouth bass lakes in Ontario · best walleye lakes in Ontario · best northern pike lakes in Ontario · best yellow perch lakes in Ontario
More water nearby: Rainy River District fishing maps (257 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.