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10,460-acre flowage near Fort Atkinson. The lake tops out around 7 ft. Depth here is modeled from the true shoreline and max depth rather than surveyed; use it to plan, not to navigate. Every species below gets its seasonal read from the same numbers driving the chart.
The outline encloses 10,654 acres, worked by 27.8 miles of shoreline. With a 1.9 development index there's bank structure worth casting at, in moderation. The whole water is littoral — nothing here runs deeper than ~15 ft, so it's all weed-and-bait territory. End to end it runs roughly 7.1 mi, about 3.8 mi across. It sits in Jefferson County. Its nearest charted neighbour, Rice Lake, is 4 mi to the northwest.
Spring puts walleye in skinny water — 2 to 7 ft is the zone. Summer fish stay in 2 to 7 ft, and winter fish hold in 2 to 7 ft. Creek inflow is the standout, an inflow / creek mouth at roughly 4 ft, rated prime for spring walleye. Plan around the evening and early morning in the warm months. A crawler harness on bottom bouncer or a deep crankbait (trolled) covers the summer program.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 7 ft | dusk & dawn | Creek inflow (4 ft) | 1/8 oz jig + minnow, Hair jig |
| Summer | 2 to 7 ft | dusk & dawn | Break off the point (3 ft) | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 2 to 7 ft | dusk & night | Break off the point (3 ft) | Jigging rap, Jig + big minnow |
| Winter | 2 to 7 ft | dusk & dawn | Deep basin (6 ft) | Jigging spoon + minnow head, Rattle bait |
Come spring, look for crappie tight to the bank in 2 to 7 ft. Through summer count on 2 to 7 ft; the winter hold is 2 to 7 ft. If you only fish one area, make it Old creek channel: a creek channel around 4 ft that scores prime in fall. 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 7 ft | midday & dawn | Shallow bay flat (3 ft) | 1/16 oz jig + tube, Curly-tail grub |
| Summer | 2 to 7 ft | dawn & dusk | Old creek channel (4 ft) | Jig trolled/spider-rigged, Small crankbait (trolled) |
| Fall | 2 to 7 ft | dawn | Old creek channel (4 ft) | Jig + minnow combo, Small swimbait (1.5-2") |
| Winter | 2 to 7 ft | midday | Deep basin (6 ft) | Tungsten jig + soft plastic, Tiny jigging spoon |
Come spring, look for white bass & hybrids tight to the bank in 1 to 7 ft. Through summer count on 2 to 7 ft; the winter hold is 2 to 7 ft. If you only fish one area, make it Creek inflow: an inflow / creek mouth around 4 ft that scores prime in spring. Best bite is early morning and the evening. A jigging spoon or a topwater (when schooling) is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 1 to 7 ft | midday & dawn | Creek inflow (4 ft) | Rooster tail / inline spinner, Curly-tail jig (white/chartreuse) |
| Summer | 2 to 7 ft | dawn & dusk | Break off the point (3 ft) | Jigging spoon, Topwater (when schooling) |
| Fall | 2 to 7 ft | midday & dawn | Main-lake point (8 ft) | Small blade bait, Jigging spoon |
| Winter | 2 to 7 ft | midday | Deep basin (6 ft) | Jigging spoon, Blade bait (vertical) |
When the water first warms, channel catfish slide up into 2 to 7 ft. There's no big seasonal slide here — summer means 2 to 7 ft, winter 2 to 7 ft. Start at Creek inflow. It's an inflow / creek mouth holding about 4 ft of water and rates prime come spring. The feeding windows run after dark and the evening.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 7 ft | dusk | Creek inflow (4 ft) | |
| Summer | 2 to 7 ft | night & dusk | Old creek channel (4 ft) | |
| Fall | 2 to 7 ft | dusk | Old creek channel (4 ft) | |
| Winter | 2 to 7 ft | midday | Deep basin (6 ft) |
Come spring, look for flathead catfish tight to the bank in 2 to 7 ft. Through summer count on 2 to 7 ft; the winter hold is 2 to 7 ft. Start at Deep basin. It's a deep basin holding about 6 ft of water and rates prime come fall. Prime time lands in after dark and the evening.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 7 ft | night & dusk | Old creek channel (4 ft) | |
| Summer | 2 to 7 ft | night & dusk | Deep basin (6 ft) | |
| Fall | 2 to 7 ft | night & dusk | Deep basin (6 ft) | |
| Winter | 2 to 7 ft | midday | Deep basin (6 ft) |
When the water first warms, largemouth bass slide up into 1 to 7 ft. There's no big seasonal slide here — summer means 2 to 7 ft, winter 2 to 7 ft. Start at Shallow bay flat. It's a weed flat holding about 3 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 | 1 to 7 ft | dawn & dusk | Shallow bay flat (3 ft) | Spinnerbait, Chatterbait |
| Summer | 2 to 7 ft | dawn & dusk | Shallow bay flat (3 ft) | Texas-rigged 10" worm, Deep-diving crankbait |
| Fall | 2 to 7 ft | midday & dawn | Old creek channel (4 ft) | Squarebill crankbait (shad), Spinnerbait |
| Winter | 2 to 7 ft | midday | Break off the point (3 ft) | Blade bait, Jigging spoon |
Lake Koshkonong also holds bluegill (2 to 7 ft in summer), freshwater drum (2 to 7 ft in summer), common carp (1 to 7 ft in summer). Pick any of them on the map above for rated spots and bait picks.
The chart marks 12 structure features on Lake Koshkonong; the deepest is Main-lake point at about 8 ft.
Access data: Wisconsin DNR — Boat Access Sites. Confirm conditions and fees locally before you launch.
Season dates, license requirements, and size and bag limits for Wisconsin waters are set by the Wisconsin DNR — and special regulations can apply to Lake Koshkonong specifically, so confirm the current rules before you fish.
Check the official Wisconsin fishing regulations →
Lake Koshkonong is about 7 ft (2 m) deep at its deepest point. The contours here are modeled from the water's real shape and maximum depth, so treat them as a rough guide.
Anglers target walleye, crappie, white bass & hybrids, channel catfish, flathead catfish, largemouth bass, bluegill, freshwater drum, common carp on Lake Koshkonong.
Creek inflow is the top-rated area: an inflow / creek mouth 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 Lake Koshkonong is regulated by the Wisconsin DNR. Check the official Wisconsin regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.
Rice Lake 4 mi · Clear Lake 5 mi · Bowers Lake 6 mi · Storrs Lake 7 mi · Red Cedar Lake 7 mi · Willies Pond 8 mi · Lake Ripley 9 mi · Spauldings Pond 10 mi · Hope Lake 11 mi · Cravath Lake 12 mi · Mud Lake 12 mi · Perch Lake 12 mi
See how Lake Koshkonong stacks up: best largemouth bass lakes in Wisconsin · best walleye lakes in Wisconsin · best crappie lakes in Wisconsin · best bluegill lakes in Wisconsin
More water nearby: Jefferson County fishing maps (14 charts). Browse all Wisconsin fishing maps or see every water on DepthScout. 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.