Mayhew Lake

Mayhew Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Cook County. 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.

Trophically, Mayhew Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. At 84 ft of maximum depth, Mayhew Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. The lake's 221 acres and 5.0 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Among the 128 graded lakes in Cook County, Mayhew Lake ranks 12 — in the top quartile locally.

Mayhew Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The fishery is panfish-dominated — bluegill, crappie, and sunfish among the 8 species documented for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. 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.