North Crab Lake

North Crab 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. A maximum depth of 35 ft puts North Crab Lake in the middle of Wisconsin's depth distribution. At 59 acres, North Crab Lake sits below the Wisconsin median: a small water where shoreline activity has an outsized effect on water quality. North Crab Lake sits at rank 117 of 202 in Vilas County, in the lower half of the local distribution.

No invasive species are currently listed at North Crab Lake — the lake remains off the Wisconsin infested-waters roster. The fishery includes walleye alongside the lake's other 6 documented species — a notable draw for Wisconsin anglers. 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.