Blackduck Lake
Beltrami County, Minnesota2,711 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Blackduck Lake. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- 28 ft max depth
- Public access
Blackduck Lake in Beltrami County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.2 ft visibility. Phosphorus: 34 µg/L. Chlorophyll-a (algae): 12.3 µg/L. Maximum depth: 28 ft. Surface area: 2711.22 acres.
Minnesota DNR's Targeted Survey on August 20, 2024 caught 0.40 walleye per trap net at Blackduck Lake. Length samples in the latest survey that recorded them ran 15–23 inches. DNR survey details →
Free interactive depth-contour map of Blackduck Lake, reaching a maximum surveyed depth of 20 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Blackduck Lake is a 2,711-acre productive, nutrient-rich eutrophic lake in Beltrami County, Minnesota with a maximum depth of 28 feet. Overall water quality is improving over recent sampling years. The lake supports 16 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 2 public boat landings. Compared to the 84 other monitored lakes in Beltrami County, Blackduck Lake ranks #69 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. Methodology: how these readings are compared.
Blackduck Lake covers about 2,700 acres in Beltrami County. It has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. The median ice-out date is April 23, which is when the open-water season begins. Vrbo is where to look for cabins and lake homes around Blackduck Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Blackduck Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Fishing16 species recorded
- Ice seasonIce-out around Apr 23
- Big water2,711 acres
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Blackduck Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Blackduck 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 Blackduck Lake
These are the measurements Minnesota PCA publishes for Blackduck Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 6.2 ft. Phosphorus 34 µg/L. Chlorophyll-a 12.3 µg/L. TSI 54.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 6.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 34µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 12.3µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 54 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Blackduck Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Blackduck Lake typically sits around 68°F at the surface in September. Summer average is about 71°F. Usually warmest in Jul (about 75°F) and coldest in May (about 55°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (55°F) to its warmest (75°F).
Typical surface water temperature by month, from 47 field readings (2016–2025) via the EPA Water Quality Portal. See the full Blackduck Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on August 20, 2024 caught 0.40 walleye per trap net at Blackduck Lake. Length samples in the latest survey that recorded them ran 15–23 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Blackduck 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
12 surveys on file from MN DNR Fisheries. Most recent: 2025-08-21 (Targeted Survey).
12 surveys on file · most recent 2025-08-21 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Yellow Perch | 32.28 | 4–8 in 2024-08-20 | 0.19 lb |
| Walleye | 10.42 | 15–23 in 2024-08-20 | 1.97 lb |
| Northern Pike | 3.22 | 7–26 in 2024-08-20 | 1.97 lb |
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.
Yellow Perch
Walleye
Northern Pike
From the 2025-08-21 survey
Minnesota DNR Fisheries IBI program staff conducted an assessment of lakeshore habitat on Blackduck Lake on August 21st, 2025, following the Score the Shore survey protocols. The assessment consisted of 106 survey sites evenly spaced 200 meters around the lake. Assessments were made in three habitat zones: Shoreline…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Blackduck Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — BlackduckFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Blackduck (1732)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — BlackduckFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — BlackduckPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
28 ft
Surface area
2,711 acres
Shoreline
13.4 mi
Littoral zone
51%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
28 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,332 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Blackduck Lake (East)Public
- Blackduck Lake (West)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Blackduck Lake
Compare lakeside cabins, hotels, and vacation rentals near Blackduck Lake in Beltrami County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Blackduck Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Blackduck Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Improving-3.01 µg/L/yr6 years
Chlorophyll-a
Improving-0.97 µg/L/yr6 years
Ice season
Typical ice-out
Apr 23
Earliest Mar 26, 2012 · Latest May 15, 2013
Typical ice-in
Nov 22
Earliest Nov 8, 2019 · Latest Dec 9, 2016
Most recent ice-out
May 5
2023
86 observations · Minnesota PCA ice records
EPA Impairment Status
Blackduck Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN04-0069-00 · Official waterbody report
Nearby Lakes in Beltrami County
Frequently asked questions about Blackduck Lake
Where is Blackduck Lake?
- Blackduck Lake is a lake in Beltrami County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Blackduck Lake?
- Blackduck Lake in Beltrami County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 6.2 ft visibility. Phosphorus: 34 µg/L. Chlorophyll-a (algae): 12.3 µg/L. Maximum depth: 28 ft. Surface area: 2711.22 acres.
Is Blackduck Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Blackduck Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Blackduck Lake?
- Blackduck Lake typically sits around 68°F at the surface in September, from 47 EPA Water Quality Portal field readings (2016–2025). That is a typical value for the month, not a live reading.
How deep is Blackduck Lake?
- Blackduck Lake has a maximum depth of 28 feet. The lake covers 2711.22 acres.
What fish are in Blackduck Lake?
- Fish species found in Blackduck Lake include black bullhead, black crappie, bluegill, brown bullhead, burbot, freshwater drum, hybrid sunfish, lake whitefish, largemouth bass, northern pike, pumpkinseed, rock bass, walleye, white sucker, yellow bullhead, yellow perch. Blackduck Lake is located in Beltrami County, Minnesota.
What did the DNR fisheries survey find at Blackduck Lake?
- Minnesota DNR's Targeted Survey on August 20, 2024 caught 0.40 walleye per trap net at Blackduck Lake. Length samples in the latest survey that recorded them ran 15–23 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Blackduck 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 Blackduck Lake thaw?
- Blackduck Lake typically has ice-out around Apr 23. Ice typically forms around Nov 22. The open water season is approximately 213 days.
Are there boat ramps on Blackduck Lake?
- Blackduck Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Blackduck Lake (East), Blackduck Lake (West). Public access is listed as yes.
Can I fish at Blackduck Lake?
- Blackduck Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. 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.
Explore Blackduck Lake across LakeQuality
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Species activity outlook by water temperature and season
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Where this data comes from
92 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA92 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate