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72-acre reservoir in Elgin County, Ontario. The lake tops out around 20 ft. The depth data here comes from the Ontario MNRF survey of 1972, a decades-old survey (a transect sounding survey). Below is the species-by-species picture, pulled from the same data the map uses.
The drawn water covers 72 acres wrapped in 2.6 miles of bank, broken up by an island. With a shoreline index of 2.2, this water is all arms and coves — edge habitat well beyond its acreage. Littoral water — the productive band under ~15 ft — makes up 97% of this chart. Tip to tip the water measures near 0.7 mi with a 0.4-mi widest point. It sits in Elgin County. Sanders Pond sits 6 mi south — the closest neighbouring chart.
Start shallow in spring: yellow perch sit in 3 to 12 ft that time of year. Warm water sends them out to 6 to 20 ft; cold water stacks them in 6 to 20 ft. Top water on the chart: Back-bay flat, a weed flat in the 7 ft range, prime in spring. Fish it in early morning and you'll meet the bite. Throw a drop-shot micro plastics or a small spoon tipped with worm until the fish tell you otherwise.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Back-bay flat (7 ft) | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 6 to 20 ft | dawn | Deep basin (15 ft) | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 6 to 20 ft | midday | Deep basin (15 ft) | Jigging spoon (small), Perch rig / spreader |
| Winter | 6 to 20 ft | midday & dawn | Deep basin (15 ft) | Tungsten jig + spikes, Rattle spoon (small) |
Come spring, look for northern pike tight to the bank in 2 to 8 ft. They move out to 8 to 20 ft in summer and finish the year down in 5 to 15 ft. If you only fish one area, make it Shallow bay flat: a weed flat around 2 ft that scores prime in spring. Best bite is early morning and the evening. A bucktail or a weedless spoon over cabbage is the honest summer answer here.
| 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 | Back-bay flat (7 ft) | Bucktail, Weedless spoon over cabbage |
| Fall | 6 to 18 ft | midday & dawn | Back-bay flat (7 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Back-bay flat (7 ft) | Tip-ups, Large jigging spoon |
Come spring, look for smallmouth bass tight to the bank in 3 to 12 ft. They move out to 6 to 20 ft in summer and finish the year down in 6 to 20 ft. If you only fish one area, make it Secondary point: a point around 9 ft that scores prime in fall. Best bite is early morning and the evening. A drop shot (goby/minnow) or a ned rig is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | dawn & dusk | Main-lake point (3 ft) | Ned rig, Tube jig |
| Summer | 6 to 20 ft | dawn & dusk | Break off the point (5 ft) | Drop shot (goby/minnow), Ned rig |
| Fall | 6 to 20 ft | midday & dawn | Secondary point (9 ft) | Jerkbait, Blade bait |
| Winter | 6 to 20 ft | midday | Break off the point (5 ft) | Blade bait, Hair jig |
When the water first warms, largemouth bass slide up into 2 to 10 ft. Summer is an 8 to 20 ft game here, winter a 6 to 20 ft one. Start at Shallow bay flat. It's a weed flat holding about 2 ft of water and rates prime come spring. The feeding windows run early morning and the evening. Keep a texas-rigged 10" worm or a deep-diving crankbait rigged through the warm months.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 10 ft | dawn & dusk | Shallow bay flat (2 ft) | Spinnerbait, Chatterbait |
| Summer | 8 to 20 ft | dawn & dusk | Back-bay flat (7 ft) | Texas-rigged 10" worm, Deep-diving crankbait |
| Fall | 4 to 15 ft | midday & dawn | Secondary point (9 ft) | Squarebill crankbait (shad), Spinnerbait |
| Winter | 6 to 20 ft | midday | Break off the point (5 ft) | Blade bait, Jigging spoon |
The spring pattern is a shallow one: rock bass in 2 to 10 ft. As the season builds they drop to 5 to 20 ft, wintering in 6 to 20 ft. Top water on the chart: Secondary point, a point in the 9 ft range, prime in summer. Time it for the evening. Summer baits: a ned rig (small) or a marabou jig gets it done.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 10 ft | midday & dawn | Main-lake point (3 ft) | 1/16 oz jig + grub, Small inline spinner |
| Summer | 5 to 20 ft | dusk | Secondary point (9 ft) | Ned rig (small), Marabou jig |
| Fall | 6 to 20 ft | midday | Break off the point (5 ft) | Small tube jig, Inline spinner |
| Winter | 6 to 20 ft | midday | Deep basin (15 ft) | Tungsten jig + plastic, Small spoon + spike |
Come spring, look for crappie tight to the bank in 2 to 8 ft. They move out to 6 to 20 ft in summer and finish the year down in 6 to 20 ft. If you only fish one area, make it Deep basin: a deep basin around 15 ft that scores prime in winter. Best bite is early morning and the evening. A jig trolled/spider-rigged or a small crankbait (trolled) is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | Shallow bay flat (2 ft) | 1/16 oz jig + tube, Curly-tail grub |
| Summer | 6 to 20 ft | dawn & dusk | Back-bay flat (7 ft) | Jig trolled/spider-rigged, Small crankbait (trolled) |
| Fall | 8 to 20 ft | dawn | Deep basin (15 ft) | Jig + minnow combo, Small swimbait (1.5-2") |
| Winter | 6 to 20 ft | midday | Deep basin (15 ft) | Tungsten jig + soft plastic, Tiny jigging spoon |
St. Thomas Reservoir also holds bluegill (4 to 15 ft in summer), pumpkinseed (2 to 10 ft in summer), brown bullhead (3 to 12 ft in summer), common carp (3 to 15 ft in summer). Pick any of them on the map above for rated spots and bait picks.
Structure-wise the chart holds 6 features, led in depth by Deep basin at roughly 15 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 St. Thomas Reservoir specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
St. Thomas Reservoir is about 20 ft (6 m) deep at its deepest point. The depth data here comes from the Ontario MNRF survey of 1972, a decades-old survey (a transect sounding survey).
Anglers target yellow perch, northern pike, smallmouth bass, largemouth bass, rock bass, crappie, bluegill, pumpkinseed, brown bullhead, common carp on St. Thomas Reservoir.
Back-bay flat is the top-rated area: a weed flat in about 7 ft of water that rates prime for yellow perch in spring. Scroll up to the map for the complete spot list by species and season.
For yellow perch, 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 St. Thomas Reservoir 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.
Sanders Pond 6 mi · Springwater Pond 8 mi · Pond Mills 10 mi · Foster Ponds 11 mi · Lake Whittaker 13 mi · Mill Pond 16 mi · Fanshawe Lake 18 mi · Sunova Lake 28 mi · Deer Cr. Re. 32 mi · Lake Hunger 37 mi · Cooley Pond 38 mi · Lake Victoria 41 mi
See how St. Thomas Reservoir stacks up: best largemouth bass lakes in Ontario · best smallmouth bass lakes in Ontario · best northern pike lakes in Ontario · best crappie lakes in Ontario
Browse all Ontario fishing maps or see every water on DepthScout. Bathymetry credit: state fisheries survey programs. 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.