Mercer Lake

On the LakeGrade rubric, Mercer Lake pulls an A: clarity at 24.6 ft and phosphorus readings still being added put it in the top bracket for Wisconsin. 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 value of 31 puts Mercer Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. 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. At 255 acres, Mercer Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Within Oneida County's 140 graded waters, Mercer Lake sits at rank 19, near the top of the local distribution.

Mercer Lake has at least one documented invasive species (Chinese Mystery Snail), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. The fishery includes walleye alongside the lake's other 6 documented species — a notable draw for Wisconsin anglers. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.