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LakeQuality
A

Crab Lake

Vilas County, WisconsinOligotrophic

Crab Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Vilas County. 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.

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. Crab Lake ranks 68 of 202 in Vilas County — solidly in the upper half of the local distribution.

No invasive species are currently listed at Crab Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Crab 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 2024-08-31. 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 32.8 ft down. Phosphorus level: 12.6 µg/L. Trophic State Index: 34.

MetricValueGrade
Water Clarity (Secchi Depth)32.8 ftA
Phosphorus12.6 µg/LA
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)34Oligotrophic

Low nutrients, clear water, excellent for swimming

Water Quality Trend: Improving

Based on 5 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Improving+1.4 m/yr4
Phosphorus Improving-0.3 µg/L/yr4
See year-by-year chart →

Location

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County Ranking

Ranked #68 of 202 lakes in Vilas County

Nearby Lakes in Vilas County

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Most recent sample: 2024-08-31

Monitoring stations: 2