Mars Lake

Mars Lake earns a D — measurements through 2025 show persistent nutrient pressure that limits clarity through the summer. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. The lake bottoms out at 24 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Mars Lake is small — 40 acres alongside partial shoreline records — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Mars Lake ranks 122 of 134 in Oneida County — at the lower end of the locally monitored distribution.

No invasive species are currently listed at Mars Lake — the lake remains off the Wisconsin infested-waters roster. The fishery includes walleye alongside the lake's other 4 documented species — a notable draw for Wisconsin anglers. A documented public access point at Mars Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.