Fish Lake
Burnett County, WisconsinOligotrophic
Fish Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.
The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Among the 70 graded lakes in Burnett County, Fish Lake ranks 10 — in the top quartile locally.
Fish Lake has no invasive species recorded in Wisconsin state databases as of 2025, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Fish Lake, which usually reflects a lack of formal fisheries survey work rather than an empty 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.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-08-27. Grade methodology: LakeGrade methodology.
Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 45.9 ft down. Phosphorus level: 12.6 µg/L. Trophic State Index: 31.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 45.9 ft | A |
| Phosphorus | 12.6 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 31 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Water Quality Trend: ↑ Improving
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.736 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.71 µg/L/yr | 6 |
Location
County Ranking
Ranked #10 of 70 lakes in Burnett County
Nearby Lakes in Burnett County
More Wisconsin Lake Rankings
Other Grade A Lakes in Wisconsin
Waukesha County · Clarity: 14.6 ft
Waukesha County · Clarity: 13.8 ft
Walworth County · Clarity: 19 ft
Washington County · Clarity: 12 ft
Kenosha County · Clarity: 10.1 ft
Washington County · Clarity: 12.5 ft
Oligotrophic Lakes in Wisconsin
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Fish Lake covering fish populations, stocking, water quality, and management. 2 reports on file.
- 2018Middle McKenzie comprehensive fisheries survey 2018Comprehensive Survey · WI DNR · 2018 (PDF)
- 2014North Sand Lake comprehensive fisheries survey, 2014Comprehensive Survey · WI DNR · 2014 (PDF)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-08-27
Monitoring stations: 2