Mauthe Lake

Mauthe Lake comes in at a B on the grading rubric — a respectable showing for a Wisconsin lake of its size and depth. Of the three parameters, phosphorus is the worst — at 54 µg/L of phosphorus, it keeps the lake susceptible to algal blooms in warm years.

The lake sits in the mesotrophic zone — the band where most well-managed Wisconsin lakes fall. The lake bottoms out at 23 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Mauthe Lake is small — 70 acres alongside partial shoreline records — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Within Fond du Lac County's 10 graded lakes, Mauthe Lake ranks 6 — below the local median, though not at the bottom.

Zebra mussels have been documented at Mauthe Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Walleye are documented at Mauthe Lake, one of 4 fish species on record for the lake. A documented public access point at Mauthe Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.