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Fishing St. Thomas Reservoir: what the data says
72-acre reservoir near Ontario. The lake tops out around 20 ft. The depth chart is built from real state fisheries GPS surveys, so the humps, channels and drop-offs you see are measured, not guessed. Below is the species-by-species picture, pulled from the same data the map uses.
Walleye fishing at St. Thomas Reservoir
Start shallow in spring: walleye sit in 4 to 15 ft that time of year. By summer they slide out to 6 to 20 ft, and by winter most fish are in 6 to 20 ft. The spot to know is Deep basin, a deep basin in about 15 ft of water that rates prime for walleye in winter. 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 | Go-to baits |
|---|---|---|---|
| Spring | 4 to 15 ft | dusk & dawn | 1/8 oz jig + minnow, Hair jig |
| Summer | 6 to 20 ft | dusk & dawn | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 6 to 20 ft | dusk & night | Jigging rap, Jig + big minnow |
| Winter | 6 to 20 ft | dusk & dawn | Jigging spoon + minnow head, Rattle bait |
Northern Pike fishing at St. Thomas Reservoir
Start shallow in spring: northern pike sit in 2 to 8 ft that time of year. Summer pushes them deeper, 8 to 20 ft, and winter fish settle into 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 covers the summer program.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | #5 inline spinner, Spoon (red/white) |
| Summer | 8 to 20 ft | dawn & dusk | Bucktail, Weedless spoon over cabbage |
| Fall | 6 to 18 ft | midday & dawn | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Tip-ups, Large jigging spoon |
Yellow Perch fishing at St. Thomas Reservoir
In spring, yellow perch run shallow here, mostly 3 to 12 ft. They move out to 6 to 20 ft in summer and finish the year down in 6 to 20 ft. Back-bay flat is the standout, a weed flat at roughly 7 ft, rated prime for spring yellow perch. Plan around early morning in the warm months. Tie on a drop-shot micro plastics or a small spoon tipped with worm and you're in the game.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 6 to 20 ft | dawn | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 6 to 20 ft | midday | Jigging spoon (small), Perch rig / spreader |
| Winter | 6 to 20 ft | midday & dawn | Tungsten jig + spikes, Rattle spoon (small) |
Smallmouth Bass fishing at St. Thomas Reservoir
Spring smallmouth bass on St. Thomas Reservoir hold shallow, usually 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. In summer the feeding windows fall in early morning and the evening. Tie on a drop shot (goby/minnow) or a ned rig and you're in the game.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 3 to 12 ft | dawn & dusk | Ned rig, Tube jig |
| Summer | 6 to 20 ft | dawn & dusk | Drop shot (goby/minnow), Ned rig |
| Fall | 6 to 20 ft | midday & dawn | Jerkbait, Blade bait |
| Winter | 6 to 20 ft | midday | Blade bait, Hair jig |
Notable structure
- Deep basin: deep basin, around 15 ft
- Secondary point: point, around 9 ft
- Back-bay flat: weed flat, around 7 ft
- Break off the point: drop-off, around 5 ft
- Main-lake point: point, around 3 ft
- Shallow bay flat: weed flat, around 2 ft
Common questions
How deep is St. Thomas Reservoir?
St. Thomas Reservoir is about 20 ft at its deepest point. The depth chart here comes from real state fisheries GPS surveys, so the contours reflect measured depths.
What fish are in St. Thomas Reservoir?
Anglers target smallmouth bass, walleye, northern pike, yellow perch on St. Thomas Reservoir.
Where is the best fishing spot on St. Thomas Reservoir?
Deep basin is the top-rated area: a deep basin in about 15 ft of water that rates prime for walleye in winter. Open the map above to see every rated spot for each species and season.
When is the best time to fish St. Thomas Reservoir?
For walleye, the summer bite is best in the evening and early morning. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.
Nearby waters
Pond Mills · Foster Ponds · Lake Whittaker · Fanshawe Lake · Mill Pond · Sunova Lake
See how St. Thomas Reservoir 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
Browse all Ontario fishing maps or every water on DepthScout. Bathymetry credit: state fisheries survey programs. How we build these maps. For fishing guidance only, never navigation.