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LakeQuality
D

Mazaska Lake

Rice County, MinnesotaEutrophic

On the scoring rubric Mazaska Lake grades a D: clarity at 2.5 ft and 49 µg/L of phosphorus keep it in the lower bracket for Rice County. Secchi readings are the weakest of the three parameters, suggesting suspended sediment or algal biomass dominates the optical signal.

At a TSI of 62, Mazaska Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. At 50 ft of maximum depth, Mazaska Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. Mazaska Lake covers 688 acres alongside 4.9 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Mazaska Lake ranks 4 of 12 in Rice County — solidly in the upper half of the local distribution.

Mazaska Lake carries an invasive watermilfoil record — boat-launch decontamination and shoreline care matter more here than at uninfested lakes. The fishery includes walleye alongside the lake's other 17 documented species — a notable draw for Minnesota anglers. A documented public access point at Mazaska Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Ice-out has been recorded 19 times at Mazaska Lake, with a median around Apr 6. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-29. Grade methodology: LakeGrade methodology.

Swimming Safety

Swimming not recommended, poor water quality with high algae risk

Water Quality Grade: D, Poor

Very murky, less than 2.5 ft of visibility. Phosphorus level: 49 µg/L. Trophic State Index: 62.

MetricValueGrade
Water Clarity (Secchi Depth)2.5 ftF
Phosphorus49 µg/LC
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)62Eutrophic

High nutrients, frequent algae, reduced clarity

Lake Details

CharacteristicValue
Maximum Depth50 ft
Average Depth13 ft
Surface Area687.68 acres
Shoreline Length4.9 mi
Littoral Zone49%
Public AccessYes

Fish Species

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

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

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

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

Invasive Species

Eurasian watermilfoil

Water Quality Trend: Declining

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

MetricTrendChange/YearYears
Water Clarity Declining-0.214 m/yr5

Ice Season

Historical ice data from Minnesota DNR (27 observations).

Typical Ice-Out
Apr 6
Typical Ice-In
Dec 1

Estimated open water season: 239 days

EarliestLatest
Ice-Out2024-03-02 (2024)2018-04-30 (2018)
Ice-In1992-11-25 (1992)2017-12-07 (2017)

Most recent ice-out: 2026-03-26

Location

Loading map…

County Ranking

Ranked #4 of 12 lakes in Rice County

Nearby Lakes in Rice County

DNR Fisheries Survey Summary

17 surveys on file from MN DNR Fisheries. Most recent: 2023-09-12 (Targeted Survey).

Top Species by Catch Rate

SpeciesAvg CPUEAvg Weight
Bluegill8722.680.21 lb
Black Crappie16.050.26 lb
Largemouth Bass10.911.29 lb
White Crappie10.030.28 lb
Yellow Perch8.910.12 lb
Freshwater Drum7.011.38 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

539 fish · 29 in · 2022-07-25
2031020trophy 1023456789

Black Crappie

80 fish · 513 in · 2022-07-25
1680trophy 105678910111213

Largemouth Bass

54 fish · 318 in · 2022-07-25
9504681012141618

White Crappie

2 fish · 812 in · 2022-07-25
10trophy 1089101112

From the 2023-09-12 survey

Minnesota DNR Fisheries IBI program staff delineated the floating leaf and emergent aquatic vegetation of Mazaska lake 09/12/2023, following the protocols listed in the MN DNR Lake Plant Mapping Manual. There were a total of 46.7 acres of floating and emergent plants mapped. This consisted of 1.9 acres of emergent…

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 Mazaska Lake. 3 reports on file.

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Lake details from Minnesota DNR LakeFinder

Ice data from Minnesota DNR Climate

Most recent sample: 2024-09-29

Monitoring stations: 2