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13,500-acre shallow lake near Celina. Ohio's largest inland lake; big crappie and channel cats. The lake tops out around 14 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. The season-by-season read for each species follows, from the map's own numbers.
Drawn out, this is 13,043 acres of water rimmed by 83.2 miles of bank, broken up by 8 islands. That shoreline is heavily fingered (development index 5.2) — bays, points and pockets everywhere, which multiplies the fishable edge. Nothing on this chart breaks 15 ft, which makes the whole surface littoral: weeds, bait and ambush cover everywhere. Figure 8.6 mi of water from one end to the other, 4.1 mi at the beam. You'll find it in Mercer County. The nearest mapped water is Lake Loramie, 14 mi to the southeast.
Spring puts largemouth bass in skinny water — 2 to 10 ft is the zone. Warm water sends them out to 4 to 14 ft; cold water stacks them in 4 to 14 ft. Weed flat is the standout, a weed flat at roughly 6 ft, rated prime for spring largemouth bass. Plan around early morning and the evening in the warm months. A texas-rigged 10" worm or a deep-diving crankbait covers the summer program.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 10 ft | dawn & dusk | Weed flat (6 ft) | Spinnerbait, Chatterbait |
| Summer | 4 to 14 ft | dawn & dusk | Break off the point (5 ft) | Texas-rigged 10" worm, Deep-diving crankbait |
| Fall | 4 to 14 ft | midday & dawn | Old creek channel (4 ft) | Squarebill crankbait (shad), Spinnerbait |
| Winter | 4 to 14 ft | midday | Break off the point (5 ft) | Blade bait, Jigging spoon |
In spring, crappie run shallow here, mostly 2 to 8 ft. Midsummer fish sit out in 4 to 14 ft before dropping to 4 to 14 ft for winter. Fall crappie concentrate at Old creek channel, a prime-rated creek channel around 4 ft. Fish it in early morning and the evening and you'll meet the bite. You won't need more than a jig trolled/spider-rigged or a small crankbait (trolled) most summer days.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | Weed flat (6 ft) | 1/16 oz jig + tube, Curly-tail grub |
| Summer | 4 to 14 ft | dawn & dusk | Old creek channel (4 ft) | Jig trolled/spider-rigged, Small crankbait (trolled) |
| Fall | 4 to 14 ft | dawn | Old creek channel (4 ft) | Jig + minnow combo, Small swimbait (1.5-2") |
| Winter | 4 to 14 ft | midday | Deep basin (9 ft) | Tungsten jig + soft plastic, Tiny jigging spoon |
Start shallow in spring: bluegill sit in 1 to 6 ft that time of year. Warm water sends them out to 4 to 14 ft; cold water stacks them in 4 to 14 ft. Top water on the chart: Shallow bay flat, a weed flat in the 1 ft range, prime in spring. Fish it in early morning and the evening and you'll meet the bite. Throw a small sponge spider (fly) or a micro tube jig until the fish tell you otherwise.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 1 to 6 ft | midday & dusk | Shallow bay flat (1 ft) | 1/32 oz jig + micro plastic, Tiny popper (evenings) |
| Summer | 4 to 14 ft | dawn & dusk | Weed flat (6 ft) | Small sponge spider (fly), Micro tube jig |
| Fall | 4 to 14 ft | midday | Weed flat (6 ft) | Micro jig + waxworm, Small spoon tipped |
| Winter | 4 to 14 ft | midday | Deep basin (9 ft) | Tungsten ice jig + plastic, Tiny spoon |
Spring puts channel catfish in skinny water — 3 to 12 ft is the zone. Warm water sends them out to 4 to 14 ft; cold water stacks them in 4 to 14 ft. Old creek channel is the standout, a creek channel at roughly 4 ft, rated prime for summer channel catfish. Plan around after dark and the evening in the warm months.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | dusk | Creek inflow (2 ft) | |
| Summer | 4 to 14 ft | night & dusk | Old creek channel (4 ft) | |
| Fall | 4 to 14 ft | dusk | Old creek channel (4 ft) | |
| Winter | 4 to 14 ft | midday | Deep basin (9 ft) |
Early season yellow perch use the shallows, holding in 3 to 12 ft. Summer is a 4 to 14 ft game here, winter a 4 to 14 ft one. The chart's best answer is Weed flat — weed flat, 6 ft, prime for spring. Best bite is early morning. Tie on a drop-shot micro plastics or a small spoon tipped with worm and you're in the game.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Weed flat (6 ft) | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 4 to 14 ft | dawn | Deep basin (9 ft) | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 4 to 14 ft | midday | Deep basin (9 ft) | Jigging spoon (small), Perch rig / spreader |
| Winter | 4 to 14 ft | midday & dawn | Deep basin (9 ft) | Tungsten jig + spikes, Rattle spoon (small) |
Start shallow in spring: common carp sit in 2 to 10 ft that time of year. Summer pushes them deeper, 3 to 14 ft, and winter fish settle into 4 to 14 ft. The spot to know is Weed flat, a weed flat in about 6 ft of water that rates prime for common carp in spring. Warm-month bites cluster around early morning and the evening.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 10 ft | midday & dawn | Weed flat (6 ft) | |
| Summer | 3 to 14 ft | dawn & dusk | Weed flat (6 ft) | |
| Fall | 4 to 14 ft | midday | Weed flat (6 ft) | |
| Winter | 4 to 14 ft | midday | Deep basin (9 ft) |
Grand Lake St. Marys also holds saugeye (4 to 14 ft in summer). Pick any of them on the map above for rated spots and bait picks.
Count 25 structure marks on this chart. The deepest, Deep basin, sits near 9 ft.
Access data: Ohio DNR — Boater & Stream Access. Confirm conditions and fees locally before you launch.
Season dates, license requirements, and size and bag limits for Ohio waters are set by the Ohio DNR Division of Wildlife — and special regulations can apply to Grand Lake St. Marys specifically, so confirm the current rules before you fish.
Check the official Ohio fishing regulations →
Grand Lake St. Marys is about 14 ft (4 m) deep at its deepest point. The depth chart here comes from real state fisheries GPS surveys, so the contours reflect measured depths.
Anglers target largemouth bass, crappie, bluegill, channel catfish, yellow perch, common carp, saugeye on Grand Lake St. Marys.
Weed flat is the top-rated area: a weed flat in about 6 ft of water that rates prime for largemouth bass in spring. Every other rated spot, per species and season, is on the map above.
For largemouth bass, 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 Grand Lake St. Marys is regulated by the Ohio DNR Division of Wildlife. Check the official Ohio regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.
Lake Loramie 14 mi · Williams Reservoir 20 mi · Bresler Reservoir 20 mi · Van Wert City Reservoir 1 23 mi · Delphos Gillmor Reservoir 26 mi · Lost Creek Reservoir 27 mi · Metzger Reservoir 28 mi · Ferguson Reservoir 28 mi · Lima Lake 29 mi · Indian Lake 33 mi · Kiser Lake 36 mi · Paulding Reservoir 42 mi
See how Grand Lake St. Marys stacks up: best largemouth bass lakes in Ohio · best saugeye lakes in Ohio · best crappie lakes in Ohio · best bluegill lakes in Ohio
Browse all Ohio 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.