Fishtrap Lake
Vilas County, WisconsinOligotrophic
Fishtrap Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Vilas County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.
A TSI value of 31 puts Fishtrap Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. Fishtrap Lake reaches 34 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. Fishtrap Lake covers 339 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Fishtrap Lake ranks 80 of 202 in Vilas County — solidly in the upper half of the local distribution.
An invasive species record — Banded Mystery Snail — has been logged at Fishtrap Lake; Wisconsin DNR maintains the official infested-waters list. Walleye are documented at Fishtrap Lake, one of 6 fish species on record for the lake. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-10-11. 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 39.4 ft down. Phosphorus level: 10.7 µg/L. Trophic State Index: 31.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 39.4 ft | A |
| Phosphorus | 10.7 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 31 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 34 ft |
| Surface Area | 339 acres |
Fish Species
Click a species to see all Wisconsin and Minnesota lakes where it is found.
→ Best fishing times for Fishtrap Lake (14-day solunar calendar)
→ Is it safe to eat fish from Fishtrap Lake? (mercury & PFAS guide)
→ Fishtrap Lake fishing regulations (limits, seasons, special rules)
Invasive Species
Water Quality Trend: ↑ Improving
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.071 m/yr | 7 |
| Phosphorus | ↑ Improving | -3.7 µg/L/yr | 4 |
Location
County Ranking
Ranked #80 of 202 lakes in Vilas County
Nearby Lakes in Vilas 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
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 2008. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Fish and recreation data from Wisconsin DNR Lakes
Most recent sample: 2025-10-11
Monitoring stations: 1