Shannon Lake

Shannon Lake comes in at a B on the grading rubric — a respectable showing for a Wisconsin lake of its size and depth. The lake's weakest score is on Secchi depth — the water looks more turbid than its phosphorus number alone would predict.

Mesotrophic conditions dominate at Shannon Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. The lake bottoms out at 37 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Shannon Lake is small — 58 acres alongside partial shoreline records — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Within Marinette County's 21 graded lakes, Shannon Lake ranks 14 — below the local median, though not at the bottom.

Shannon Lake has no invasive species recorded in Wisconsin state databases as of 2022, though prevention practices still apply at all access points. The lake's fish records list 1 species — a varied community without one dominant gamefish. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.