Mary Lake
Hubbard County, Minnesota235 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Mary Lake. Here is what has been measured.
- 48 ft max depth
- Public access
- Limited data
Mary Lake in Hubbard County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 18.8 ft visibility. Maximum depth: 48 ft. Surface area: 235.22 acres.
Minnesota DNR's Targeted Survey on July 6, 2021 caught 17.68 largemouth bass per hour of electrofishing at Mary Lake. DNR survey details →
Mary Lake is a 235-acre lake in Hubbard County, Minnesota with a maximum depth of 48 feet. Overall water quality is improving over recent sampling years. The lake supports 14 documented fish species including black crappie, bluegill, and brown bullhead. Public access is available.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-07. Methodology: how these readings are compared.
What Mary Lake is good for
From access and monitoring records, not editorial picks.
- Clear water18.8 ft of visibility
- Fishing14 species recorded
- Ice seasonIce-out around Apr 24
- Deep water48 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Mary Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Mary Lake
These are the measurements Minnesota PCA publishes for Mary Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 18.8 ft down. TSI 35.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 18.8ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 35 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Mary Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Mary Lake typically sits around 62°F at the surface in October. Summer average is about 73°F. Usually warmest in Jul (about 75°F) and coldest in May (about 61°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (61°F) to its warmest (75°F).
Typical surface water temperature by month, from 31 field readings (2023–2025) via the EPA Water Quality Portal. See the full Mary Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on July 6, 2021 caught 17.68 largemouth bass per hour of electrofishing at Mary Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mary Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2023-07-31 (Targeted Survey).
8 surveys on file · most recent 2023-07-31 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 14.56 | 3–8 in 2021-06-29 | 0.16 lb |
| Green Sunfish | 10.40 | 5–7 in 2021-06-29 | 0.25 lb |
| Bluntnose Minnow | 7.34 |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
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
Green Sunfish
From the 2023-07-31 survey
A temperature-dissolved oxygen profile was collected in the deepest basin on Big LaSalle Lake on July 31, 2023, to evaluate the amount of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee. Based on the profile, the top of the thermocline (i.e., the location in the water…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Mary Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Big LaSalleFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Big LaSalle (1317)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — Big LaSalleFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Big LaSallePublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
48 ft
Surface area
235 acres
Shoreline
3.3 mi
Littoral zone
17%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
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Stays near Mary Lake
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Fish Species
Click a species to see every lake where it is documented.
Fishing Mary Lake
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Improving6 years
Phosphorus
Worsening+0.29 µg/L/yr6 years
Chlorophyll-a
Improving-0.34 µg/L/yr6 years
Ice season
Typical ice-out
Apr 24
Earliest Apr 15, 1992 · Latest May 6, 1996
Typical ice-in
Nov 18
Earliest Nov 7, 1991 · Latest Dec 10, 1999
Most recent ice-out
May 1
2018
14 observations · Minnesota PCA ice records
Nearby Lakes in Hubbard County
Frequently asked questions about Mary Lake
Where is Mary Lake?
- Mary Lake is a lake in Hubbard County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Mary Lake?
- Mary Lake in Hubbard County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 18.8 ft visibility. Maximum depth: 48 ft. Surface area: 235.22 acres.
Is Mary Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Mary Lake?
- Mary Lake typically sits around 62°F at the surface in October, from 31 EPA Water Quality Portal field readings (2023–2025). That is a typical value for the month, not a live reading.
How deep is Mary Lake?
- Mary Lake has a maximum depth of 48 feet. The lake covers 235.22 acres.
What fish are in Mary Lake?
- Fish species found in Mary Lake include black crappie, bluegill, brown bullhead, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Mary Lake is located in Hubbard County, Minnesota.
What did the DNR fisheries survey find at Mary Lake?
- Minnesota DNR's Targeted Survey on July 6, 2021 caught 17.68 largemouth bass per hour of electrofishing at Mary Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mary Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
When does Mary Lake thaw?
- Mary Lake typically has ice-out around Apr 24. Ice typically forms around Nov 18. The open water season is approximately 208 days.
Can I fish at Mary Lake?
- Public access to Mary Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
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Where this data comes from
31 measurements from 1 monitoring station, 2023–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA31 samples · 2023–2025
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate