Spider Lake

Spider Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI near 44 places Spider Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. The lake bottoms out at 36 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. With 1,392 acres of surface and 20.6 miles of shoreline, Spider Lake is a large water by Minnesota standards — recreational pressure is spread across a long shoreline. Among the 141 graded lakes in Itasca County, Spider Lake sits at rank 67, above the county median.

Spider Lake has at least one documented invasive species (flowering rush), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. Spider Lake's fishery is anchored by muskellunge, with 14 documented species in total — a destination water for muskie anglers. Public access is available — the lake is on the Minnesota PCA public-access list. Ice-out has been recorded 11 times at Spider Lake, with a median around Apr 21. 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.