What You'll Find at Upper Nemahbin Lake

Upper Nemahbin Lake is a 235-acre glacial lake in Oconomowoc with a maximum depth of 85 feet—the deepest water in the Oconomowoc chain. That depth matters. It creates distinct seasonal patterns that separate this lake from its shallower neighbors, and it holds walleye and northern pike year-round rather than forcing them to migrate. The lake sits just north of Lower Nemahbin, connected by a narrow channel that most anglers ignore, which means Upper Nemahbin stays quieter and less pressured than the main Oconomowoc lakes.

The bottom is a mix of sand, gravel, and muck. The deepest basin runs roughly north to south through the middle of the lake, with a secondary deep pocket on the eastern side. Shallow bays on the north and west ends hold weeds in summer and attract spawning walleye in spring. If you're coming from Lower Nemahbin or the main Oconomowoc lakes, Upper Nemahbin rewards anglers who slow down and fish vertically rather than casting shallow structure.

Key Takeaways

  • Upper Nemahbin's 85-foot maximum depth holds walleye and pike year-round, with spring spawning concentrated in the north and west bays.
  • Summer walleye suspend over the deep basin in 40 to 60 feet of water, requiring live bait presentations or vertical jigging rather than casting.
  • Fall turnover (typically late September through October) pushes walleye into shallower structure as water temperature equalizes, making this the most accessible season for shore and boat anglers.
  • The lake is accessible by boat launch at the Oconomowoc Parks Department facility on Lower Nemahbin, with a short channel connecting the two lakes.
  • Pike fishing peaks in spring and fall when fish move into shallow bays; summer pike hold in deeper water or weed edges during low-light hours.

Spring Walleye: Spawning Bays and Shallow Structure

Walleye spawn in Upper Nemahbin from mid-April through May, and the north and west bays are where it happens. These shallow areas—typically 4 to 12 feet—warm faster than the deep basin, and spawning fish move in predictably. Jigs tipped with live shiners or crawlers work well in these bays, and you don't need to cast far; fish are concentrated and aggressive.

The channel connecting Upper and Lower Nemahbin also funnels spawning walleye, and many anglers overlook this transition zone. Fish moving between lakes use the channel as a highway, and a 1/4-ounce jig worked slowly along the 8- to 15-foot drop can produce steady action. Water temperature is the trigger: when the lake reaches 48 to 52 degrees Fahrenheit, spawning activity peaks. Check the Wisconsin DNR's weekly lake temperature reports for Oconomowoc to time your trip.

Summer: Deep Basin and Suspended Fish

By late June, walleye abandon the bays and move to the deep basin. Upper Nemahbin's depth advantage becomes clear here—the thermocline (the layer where temperature drops sharply) typically forms between 35 and 50 feet, and walleye suspend just above it or hold on the bottom below it. This is not casting water. You need a boat with a sonar unit, live bait on a slip sinker rig, or a vertical jigging approach.

Live shiners suspended 5 to 10 feet above the bottom in 45 to 60 feet of water produce consistently through July and August. Work the deepest part of the basin slowly, and don't move fast—walleye in summer are lethargic and won't chase. If you prefer jigging, 1/2-ounce to 3/4-ounce jigs with live bait work better than plastics in deep water; the weight gets you down quickly and the live bait triggers bites in low-light conditions. Early morning and late evening are most productive, but unlike shallower lakes, Upper Nemahbin's depth means you can find active fish at midday if you're willing to go deep.

Fall Turnover: The Most Accessible Season

Late September through October is when Upper Nemahbin becomes easiest to fish. As water temperature cools and the thermocline breaks down, walleye move back into shallower structure—the 15- to 30-foot zone around the basin edges and the deeper parts of the bays. This is the window when shore anglers and anglers in smaller boats can compete with deep-water specialists.

Jigs and live bait work in 20 to 35 feet of water along the drop-offs on the eastern and southern sides of the lake. Casting crankbaits that reach 15 to 25 feet can also be effective, especially early and late in the day. The water is cooling but still holds enough oxygen throughout the water column that fish aren't confined to narrow bands. By late October, as water temperature approaches 50 degrees, walleye begin moving toward winter structure—deeper holes and the basin—but the transition period offers the best combination of accessibility and consistent action.

Northern Pike: Spring and Fall Shallow Water

Pike in Upper Nemahbin follow a predictable pattern tied to water temperature and weed growth. Spring pike move into the north and west bays as soon as ice clears, hunting spawning walleye and other forage. Large spinnerbaits (1/2 to 3/4 ounce) and crankbaits in 4 to 15 feet of water produce strikes. Pike are aggressive in spring and don't require subtle presentations; they're looking for an easy meal.

Summer pike are harder to locate. Some hold in deeper water during the day, but most are in the weed edges and shallow bays during low-light hours—early morning, late evening, and overcast days. If you're targeting pike in July and August, focus on the weed lines in 8 to 20 feet of water at dawn and dusk. Fall brings pike back into the shallows as water cools and weeds begin to die back. October pike fishing can be excellent in the bays and along the weed edges, with the same presentations that work in spring.

Winter: Ice Fishing and Deep-Water Jigging

Upper Nemahbin's depth makes it a solid winter walleye lake. Once ice forms (typically mid-December), the deep basin becomes the primary holding area. Walleye suspend in 40 to 60 feet of water, and vertical jigging with live minnows or spoons is the standard approach. Tip-ups with live shiners also work, but they require patience—fish are less active in winter, and bites can be slow.

Pike are less predictable in winter. Some hold in the deep basin with walleye, but others remain in deeper parts of the bays where there's slightly more oxygen. If you're ice fishing for pike, try the 20- to 35-foot zone along the bay edges before committing to the deepest water. Check current ice thickness reports from the Oconomowoc Parks Department before heading out; Upper Nemahbin's depth means ice can be uneven, and thinner ice may persist over the deepest basin.

Access and Regulations

Upper Nemahbin is accessed by boat launch only. The Oconomowoc Parks Department maintains a public launch on Lower Nemahbin, and the short channel between the two lakes is navigable year-round (except during winter when ice closes it). There is no shore fishing access on Upper Nemahbin itself, though Lower Nemahbin has limited shore access at the launch area.

Wisconsin fishing regulations apply. Walleye have a 15-inch minimum size limit and a daily bag limit of five fish. Northern pike have an 24-inch minimum size limit and a daily bag limit of one fish. A Wisconsin fishing license is required for anyone 16 and older. Consult the current Wisconsin DNR fishing regulations before your trip, as rules can change annually.

Frequently Asked Questions

What's the difference between Upper and Lower Nemahbin for walleye fishing?

Upper Nemahbin is deeper (85 feet vs. 50 feet) and holds walleye year-round in the deep basin. Lower Nemahbin is shallower and more weed-oriented, making it better for summer casting. Upper Nemahbin requires more vertical jigging and live bait presentations, especially in summer.

Can I fish Upper Nemahbin from shore?

No. Upper Nemahbin has no public shore access. You must launch a boat from the Lower Nemahbin facility. If you don't have a boat, Lower Nemahbin offers limited shore fishing at the launch area.

When is the best time to fish Upper Nemahbin?

Fall turnover (late September through October) is most accessible because walleye move into 15- to 30-foot water. Spring (mid-April through May) is excellent for spawning walleye in the bays. Summer requires deep-water techniques and sonar. Winter ice fishing is productive but requires ice safety precautions.

Do I need a sonar unit to fish Upper Nemahbin?

Not required, but it helps significantly in summer when walleye suspend in deep water. Spring and fall fishing in shallower structure can be productive without sonar. Winter ice fishing with tip-ups doesn't require sonar either.

What size pike are in Upper Nemahbin?

Pike in Upper Nemahbin range from 18 to 30 inches, with occasional fish larger than 30 inches. The 24-inch minimum size limit protects younger fish. Spring and fall are the most consistent seasons for pike action.