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LakeQuality
A

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.

MetricValueGrade
Water Clarity (Secchi Depth)39.4 ftA
Phosphorus10.7 µg/LA
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)31Oligotrophic

Low nutrients, clear water, excellent for swimming

Lake Details

CharacteristicValue
Maximum Depth34 ft
Surface Area339 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

Banded Mystery SnailChinese Mystery SnailRusty Crayfish

Water Quality Trend: Improving

Based on 7 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Stable+0.071 m/yr7
Phosphorus Improving-3.7 µg/L/yr4
See year-by-year chart →

Location

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County Ranking

Ranked #80 of 202 lakes in Vilas County

Nearby Lakes in Vilas County

WI DNR Lake Profile

Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 2008. 1 station on file (most recent sample 2025).

DNR Assessment
Excellent · Deep Lowland lake
Trophic State Index 41 (mesotrophic) · 5-year average

Fish Species (DNR-rated)

Musky(Common)Panfish(Common)Largemouth Bass(Common)Walleye(Common)Smallmouth Bass(Present)Northern Pike(Present)

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