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.
3,286-acre lake near St. Louis County. The lake tops out around 15 ft. The depth chart comes from Minnesota Department of Natural Resources bathymetric survey data, so the contours are survey-derived rather than computer-modeled. The depth data here comes from the Minnesota DNR survey of 1965, a decades-old survey (the DNR's original lake-survey map). Species by species, here's what the data says the year looks like.
The outline encloses 3,281 acres, worked by 33.9 miles of shoreline — 3 islands included. That shoreline is heavily fingered (development index 4.2) — bays, points and pockets everywhere, which multiplies the fishable edge. The basin spans about 4.6 mi end to end and 2.8 mi across at its widest. It sits in St. Louis County. Island Lake Rsvr(E.Basin) sits 4 mi southeast — the closest neighbouring chart.
Start shallow in spring: walleye sit in 4 to 15 ft that time of year. They don't go far with the seasons — 5 to 15 ft covers summer, 5 to 15 ft covers winter. Top water on the chart: Gravel shoal, a gravel shoal in the 4 ft range, prime in spring. Fish it in the evening and early morning and you'll meet the bite. Throw a crawler harness on bottom bouncer or a deep crankbait (trolled) until the fish tell you otherwise.
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 | Gravel shoal (4 ft) | 1/8 oz jig + minnow, Hair jig |
| Summer | 5 to 15 ft chart-limited; documented 15 to 35 ft | dusk & dawn | Break off the point (5 ft) | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 5 to 15 ft chart-limited; documented 12 to 40 ft | dusk & night | Break off the point (5 ft) | Jigging rap, Jig + big minnow |
| Winter | 5 to 15 ft chart-limited; documented 20 to 40 ft | dusk & dawn | Deep basin (15 ft) | Jigging spoon + minnow head, Rattle bait |
Spring puts yellow perch in skinny water — 3 to 12 ft is the zone. Warm water sends them out to 5 to 15 ft; cold water stacks them in 5 to 15 ft. Deep basin is the standout, a deep basin at roughly 15 ft, rated prime for fall yellow perch. Plan around early morning in the warm months. A drop-shot micro plastics or a small spoon tipped with worm covers the summer program.
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 (2 ft) | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 5 to 15 ft chart-limited; documented 10 to 30 ft | dawn | Deep basin (15 ft) | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 5 to 15 ft chart-limited; documented 12 to 35 ft | midday | Deep basin (15 ft) | Jigging spoon (small), Perch rig / spreader |
| Winter | 5 to 15 ft chart-limited; documented 15 to 35 ft | midday & dawn | Deep basin (15 ft) | Tungsten jig + spikes, Rattle spoon (small) |
Spring northern pike on Boulder hold shallow, usually 2 to 8 ft. They move out to 5 to 15 ft in summer and finish the year down in 5 to 15 ft. Put Shallow bay flat first on the milk run — a weed flat near 2 ft that grades prime for spring. The feeding windows run early morning and the evening. The summer box starts with a bucktail or a weedless spoon over cabbage.
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 | 2 to 8 ft | midday & dawn | Shallow bay flat (2 ft) | #5 inline spinner, Spoon (red/white) |
| Summer | 5 to 15 ft chart-limited; documented 8 to 20 ft | dawn & dusk | Break off the point (5 ft) | Bucktail, Weedless spoon over cabbage |
| Fall | 5 to 15 ft chart-limited; documented 6 to 18 ft | midday & dawn | Break off the point (5 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Shoreline point (5 ft) | Tip-ups, Large jigging spoon |
Spring puts rock bass in skinny water — 2 to 10 ft is the zone. As the season builds they drop to 4 to 15 ft, wintering in 5 to 15 ft. Spring rock bass concentrate at Gravel shoal, a prime-rated gravel shoal around 4 ft. Warm-month bites cluster around the evening. A ned rig (small) or a marabou jig covers the summer program.
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 | 2 to 10 ft | midday & dawn | Gravel shoal (4 ft) | 1/16 oz jig + grub, Small inline spinner |
| Summer | 4 to 15 ft chart-limited; documented 5 to 20 ft | dusk | Shoreline point (4 ft) | Ned rig (small), Marabou jig |
| Fall | 5 to 15 ft chart-limited; documented 8 to 22 ft | midday | Break off the point (5 ft) | Small tube jig, Inline spinner |
| Winter | 5 to 15 ft chart-limited; documented 12 to 30 ft | midday | Deep basin (15 ft) | Tungsten jig + plastic, Small spoon + spike |
Spring crappie on Boulder hold shallow, usually 2 to 8 ft. They move out to 5 to 15 ft in summer and finish the year down in 5 to 15 ft. Put Deep basin first on the milk run — a deep basin near 15 ft that grades prime for winter. The feeding windows run early morning and the evening. The summer box starts with a jig trolled/spider-rigged or a small crankbait (trolled).
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 | 2 to 8 ft | midday & dawn | Shallow bay flat (2 ft) | 1/16 oz jig + tube, Curly-tail grub |
| Summer | 5 to 15 ft chart-limited; documented 10 to 25 ft | dawn & dusk | Break off the point (5 ft) | Jig trolled/spider-rigged, Small crankbait (trolled) |
| Fall | 5 to 15 ft chart-limited; documented 8 to 20 ft | dawn | Break off the point (5 ft) | Jig + minnow combo, Small swimbait (1.5-2") |
| Winter | 5 to 15 ft chart-limited; documented 15 to 35 ft | midday | Deep basin (15 ft) | Tungsten jig + soft plastic, Tiny jigging spoon |
Spring puts pumpkinseed in skinny water — 1 to 8 ft is the zone. As the season builds they drop to 2 to 10 ft, wintering in 5 to 15 ft. Spring pumpkinseed concentrate at Shallow bay flat, a prime-rated weed flat around 2 ft. Warm-month bites cluster around the evening and early morning. A micro tube or a sponge spider (fly) covers the summer program.
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 | 1 to 8 ft | midday & dusk | Shallow bay flat (2 ft) | Micro jig under a float, Tiny beetle-spin |
| Summer | 2 to 10 ft | dusk & dawn | Shallow bay flat (2 ft) | Micro tube, Sponge spider (fly) |
| Fall | 4 to 14 ft | dusk & dawn | Shallow bay flat (2 ft) | Micro jig + waxworm, Small spoon tipped |
| Winter | 5 to 15 ft chart-limited; documented 6 to 18 ft | dawn | Deep basin (15 ft) | Tungsten ice jig + plastic, Tiny spoon |
Boulder also holds bluegill (4 to 15 ft in summer), burbot (5 to 15 ft in summer), black bullhead (3 to 15 ft in summer). Pick any of them on the map above for rated spots and bait picks.
14 pieces of structure are mapped here — Deep basin, around 15 ft, is the deepest of them.
Access data: MN DNR Water Access Sites (struc_water_access_sites), Minnesota Geospatial Commons. Confirm conditions and fees locally before you launch.
Season dates, license requirements, and size and bag limits for Minnesota waters are set by the Minnesota DNR — and special regulations can apply to Boulder specifically, so confirm the current rules before you fish.
Check the official Minnesota fishing regulations →
Boulder is about 15 ft (5 m) deep at its deepest point. The depth data here comes from the Minnesota DNR survey of 1965, a decades-old survey (the DNR's original lake-survey map).
Anglers target walleye, yellow perch, northern pike, rock bass, crappie, pumpkinseed, bluegill, burbot, black bullhead on Boulder.
Gravel shoal is the top-rated area: a gravel shoal in about 4 ft of water that rates prime for walleye in spring. Scroll up to the map for the complete spot list by species and season.
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.
Fishing on Boulder is regulated by the Minnesota DNR. Check the official Minnesota regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.
Island Lake Rsvr(E.Basin) 4 mi · Island Lake Rsvr(W.Basin) 4 mi · Morgan 5 mi · Jacobs 5 mi · Schultz 5 mi · Flowage 5 mi · Thompson 5 mi · Cooks 6 mi · Horseshoe 6 mi · Sunshine 6 mi · Mirror 7 mi · Clearwater 7 mi
See how Boulder stacks up: best walleye lakes in Minnesota · best northern pike lakes in Minnesota · best crappie lakes in Minnesota · best bluegill lakes in Minnesota
More water nearby: St. Louis County fishing maps (429 charts). Browse all Minnesota 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.