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.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | F |
| Phosphorus | 49 µg/L | C |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 50 ft |
| Average Depth | 13 ft |
| Surface Area | 687.68 acres |
| Shoreline Length | 4.9 mi |
| Littoral Zone | 49% |
| Public Access | Yes |
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
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.214 m/yr | 5 |
Ice Season
Historical ice data from Minnesota DNR (27 observations).
Estimated open water season: 239 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-02 (2024) | 2018-04-30 (2018) |
| Ice-In | 1992-11-25 (1992) | 2017-12-07 (2017) |
Most recent ice-out: 2026-03-26
Location
County Ranking
Ranked #4 of 12 lakes in Rice County
Nearby Lakes in Rice County
More Minnesota Lake Rankings
State Parks Near Mazaska Lake
Other Grade D Lakes in Minnesota
Eutrophic Lakes in Minnesota
DNR Fisheries Survey Summary
17 surveys on file from MN DNR Fisheries. Most recent: 2023-09-12 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 8722.68 | 0.21 lb |
| Black Crappie | 16.05 | 0.26 lb |
| Largemouth Bass | 10.91 | 1.29 lb |
| White Crappie | 10.03 | 0.28 lb |
| Yellow Perch | 8.91 | 0.12 lb |
| Freshwater Drum | 7.01 | 1.38 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
Black Crappie
Largemouth Bass
White Crappie
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…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Mazaska Lake. 3 reports on file.
- —Fisheries Lake Survey — MazaskaFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — MazaskaFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — MazaskaPublic Water Access Sites · MN DNR LakeFinder
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