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Crooked Lake

Oconto County, WisconsinMesotrophic

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

Mesotrophic conditions dominate at Crooked Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. The lake bottoms out at 37 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Crooked Lake covers 162 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Crooked Lake ranks 21 of 62 in Oconto County — solidly in the upper half of the local distribution.

Zebra mussels have been documented at Crooked Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. The fishery is bass-led, with 3 documented species across the lake's records. Public access is available — the lake is on the Wisconsin DNR public-access list. 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 2025-08-26. Grade methodology: LakeGrade methodology.

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Swimming Safety

Excellent for swimming, crystal clear water with minimal algae

Water Quality Grade: A, Excellent

Good clarity, visible to about 11 ft. Phosphorus level: 11.8 µg/L. Trophic State Index: 41.

MetricValueGrade
Water Clarity (Secchi Depth)11 ftB
Phosphorus11.8 µg/LA
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)41Mesotrophic

Moderate nutrients, good water quality

Lake Details

CharacteristicValue
Maximum Depth37 ft
Surface Area162 acres
Public AccessYes

Fish Species

Click a species to see every graded lake where it is documented.

→ Best fishing times for Crooked Lake (14-day solunar calendar)

→ Is it safe to eat fish from Crooked Lake? (mercury & PFAS guide)

Crooked Lake fishing regulations (limits, seasons, special rules)

Invasive & Introduced Species

Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.

Banded Mystery SnailChinese Mystery SnailCurly-Leaf PondweedEurasian Water-MilfoilPurple LoosestrifeZebra Mussel

Water Quality Trend: Stable

Based on 6 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Declining-0.543 m/yr6
Phosphorus Improving-0.29 µg/L/yr6
See year-by-year chart →

Recreation & Access

1
Boat Landings
Yes
Public Access

Location

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County Ranking

Ranked #21 of 62 lakes in Oconto County

Nearby Lakes in Oconto County

WI DNR Lake Profile

Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1993. 4 stations on file (most recent sample 2025).

DNR Assessment
Excellent · Deep Headwater lake
Trophic State Index 40 (oligotrophic) · 5-year average

Fish Species (DNR-rated)

Largemouth Bass(Common)Northern Pike(Common)Panfish(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

Public boat-access points from the USGS National Boat Ramps inventory

Most recent sample: 2025-08-26

Monitoring stations: 1

Where to stay near Crooked Lake

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