Fenner Lake

Fenner Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Marquette County. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI near 43 places Fenner Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. The lake bottoms out at 18 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. At 41 acres, Fenner Lake sits below the Wisconsin median: a small water where shoreline activity has an outsized effect on water quality. Fenner Lake ranks 4 of 13 in Marquette County — solidly in the upper half of the local distribution.

Fenner Lake carries an invasive watermilfoil record — boat-launch decontamination and shoreline care matter more here than at uninfested lakes. Bass fishing is part of the appeal: the species list runs to 3, anchored by largemouth and/or smallmouth bass. Public access is available — the lake is on the Wisconsin DNR public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.