Grass Lake

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Size

4ac

Boat Launch

Carry-in Launch

Toilet

Boat Dock

Overview

The state's second largest lake, widely known for exciting spring walleye runs. Good numbers of white bass and crappie offer steady action. Muskie, bass and pike also available..

Grass Lake Map

Fishing Regulations

Special Fishing Regulations: This lake has special fishing regulations that differ from statewide or border water regulations for those species identified below and take precedence. Regulations listed below are currently in place. Visit the fishing regulations page for links to upcoming regulations for specific lakes.

Special Species Regulations

Bullheads: Open All Year: No minimum length limit and the daily bag limit is unlimited.
Catfish: Open All Year: No minimum length limit and the daily bag limit is 10.
Cisco And Whitefish: Open All Year: No minimum length limit and the daily bag limit is 10.
Lake Sturgeon: Closed: No fishing allowed.
Largemouth Bass And Smallmouth Bass: May 2, 2026 to March 7, 2027: The minimum length limit is 14” and the daily bag limit is 5.
Muskellunge And Hybrids: May 2, 2026 to December 31, 2026 on open water: The minimum length limit is 40” and the daily bag limit is 1.
Northern Pike: May 2, 2026 to March 7, 2027: The minimum length limit is 26” and the daily bag limit is 2.
Paddlefish: Closed: No fishing allowed.
Panfish: Open All Year: No minimum length limit and the daily bag limit is 25.
Rock, Yellow, And White Bass: Open All Year: No minimum length limit and the daily bag limit is unlimited.
Rough Fish: Open All Year: No minimum length limit and the daily bag limit is unlimited.
Round Goby: Open All Year: The daily bag limit is 0, one may be killed and possessed for transport to a WDNR Office.
Ruffe: Open All Year: The daily bag limit is 0, one may be killed and possessed for transport to a WDNR Office.
Shovelnose Sturgeon: Closed: No fishing allowed.
Trout: See specific regulations: See Trout Regulations
Walleye, Sauger, And Hybrids: May 2, 2026 to March 7, 2027: The minimum length limit is 15” and the daily bag limit is 3.
White Perch: Open All Year: The daily bag limit is 0, one may be killed and possessed for transport to a WDNR Office.

Features

Petenwell flowage was created in the late 1940’s and became the second largest inland lake in Wisconsin. The dam that blocks the Wisconsin River to form the Petenwell Flowage was created to provide hydroelectric power and flood control. Petenwell is heavily used for many recreational activities such as: boating, fishing, swimming, hunting and canoeing/kayaking. The flowage provides many opportunities for shore anglers at a variety of locations. The Petenwell Flowage has an annual catch and release muskie tournament founded by Todd Forcier and has also hosted bowfishing tournaments for rough fish. Stumps, submerged timber and shallow water make parts of the flowage difficult to navigate. Many of these hazards are not marked on this map or with buoys. Careful navigation should be used, especially in the upper third of the flowage. A navigational channel is marked with buoys from Browns Creek outlet area downstream to Yellow Banks and from Devils Elbow to the Wisconsin River channel. Buoys have also been placed along the edge of Strongs Prairie Flats to indicate the shallow and dangerous area east of the buoys. Almost the entire shoreline of Petenwell is open to public use, with a few exceptions. The public access is from the shoreline back 100 feet. This strip is marked with signs and has walking trails. The exceptions to public access are well marked.

Forage

Small suckers and other small rough fish are heavily preyed upon by muskie. Biologists believe the recent unwanted addition of freshwater drum may also provide a food source for large game fish in the future. Young panfish and white bass are food sources for many game species. Emerald shiner, bluntnose minnow, and log-perch make up the diets for a variety of species.

Seasonal Movements

Walleye congregate below the Nekoosa Dam on the Wisconsin River from mid-March through April to spawn. Creek inlets that have adequate water flow will also attract spring walleye. A second migration of walleye to the Nekoosa Dams also occurs in late September and October. Better foraging is the primary reason for the second migration. White bass will be concentrated below the Nekoosa Dam during mid-May until the end of June.