Mercer Lake

Mercer Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.

The lake sits in the mesotrophic zone — the band where most well-managed Wisconsin lakes fall. Mercer Lake reaches 24 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 181 acres, Mercer Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Within Iron County's 33 graded waters, Mercer Lake sits at rank 5, near the top of the local distribution.

Mercer Lake has at least one documented invasive species (Banded Mystery Snail), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. Walleye are documented at Mercer Lake, one of 7 fish species on record for the lake. 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.