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B

Ann Lake

Carver County, MinnesotaMesotrophic

On the LakeGrade scale Ann Lake grades a B, with clarity at 9.2 ft and 28 µg/L of phosphorus placing it above the Minnesota median. With clarity and phosphorus scored, the sub-grades cluster within a letter of each other, pointing to stable conditions rather than one specific stressor.

The lake sits in the mesotrophic zone — the band where most well-managed Minnesota lakes fall. A maximum depth of 45 ft puts Ann Lake in the middle of Minnesota's depth distribution. The lake's 116 acres and 1.7 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Within Carver County's 40 graded waters, Ann Lake sits at rank 9, near the top of the local distribution.

Zebra mussel presence at Ann Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The fishery is bass-led, with 11 documented species across the lake's records. Public access is available — the lake is on the Minnesota PCA 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, Minnesota DNR LakeFinder, last sampled 2024-09-25. Grade methodology: LakeGrade methodology.

Reviewed by LakeQuality Editorial Team · Updated

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Swimming Safety

Good for swimming, clear water with low algae levels

Water Quality Grade: B, Good

Moderate clarity, visible to about 9.2 ft. Phosphorus level: 28 µg/L. Trophic State Index: 49.

MetricValueGrade
Water Clarity (Secchi Depth)9.2 ftC
Phosphorus28 µg/LB
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)49Mesotrophic

Moderate nutrients, good water quality

Lake Details

CharacteristicValue
Maximum Depth45 ft
Surface Area115.74 acres
Shoreline Length1.7 mi
Littoral Zone39%
Public AccessYes

Fish Species

black bullhead,black crappie,bluegill,brown bullhead,green sunfish,hybrid sunfish,largemouth bass,northern pike,pumpkinseed,yellow bullhead,yellow perch

Click a species to see all Minnesota and Wisconsin lakes where it is found.

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

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

Ann 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.

Eurasian watermilfoilbrittle naiadzebra mussel

Water Quality Trend: Improving

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

MetricTrendChange/YearYears
Water Clarity Stable+0.024 m/yr5
Phosphorus Improving-2.57 µg/L/yr3
See year-by-year chart →

Ice Season

Historical ice data from Minnesota DNR (4 observations).

Typical Ice-Out
Apr 11
EarliestLatest
Ice-Out2025-04-03 (2025)2022-04-11 (2022)
Ice-In2024-12-08 (2024)2022-12-18 (2022)

Most recent ice-out: 2025-04-03

Location

Loading map…

County Ranking

Ranked #9 of 40 lakes in Carver County

Nearby Lakes in Carver County

DNR Fisheries Survey Summary

13 surveys on file from MN DNR Fisheries. Most recent: 2023-08-16 (Targeted Survey).

Top Species by Catch Rate

SpeciesAvg CPUEAvg Weight
CNM53.49
Bluegill45.030.16 lb
Bluntnose Minnow11.30
Largemouth Bass6.771.46 lb
Black Bullhead5.740.51 lb
Green Sunfish4.830.08 lb

CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.

Length Distributions

Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.

Bluegill

91 fish · 38 in · 2023-08-16
42210345678

Largemouth Bass

1 fish · 66 in · 2023-08-16
106

Black Bullhead

1 fish · 1212 in · 2022-05-31
1012

Green Sunfish

2 fish · 44 in · 2023-08-16
2104

From the 2023-08-16 survey

A targeted survey of nearshore fish species in Ann Lake was conducted on August 16-22, 2023, by Index of Biological Integrity (IBI) Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible. Backpack…

Source: MN DNR LakeFinder Fisheries Lake Survey

DNR Reports & Resources

Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Ann Lake. 2 reports on file.

EPA Impairment Status

Ann Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).

Causes of impairment

Mercury

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit MN10-0012-00 · Official waterbody report

Data Sources

Water quality data from the EPA Water Quality Portal

Impairment status from EPA ATTAINS 303(d) database

Grading methodology based on Metropolitan Council standards

Lake details from Minnesota DNR LakeFinder

Ice data from Minnesota DNR Climate

Most recent sample: 2024-09-25

Monitoring stations: 2