Blackduck Lake
Blackduck Lake in Beltrami County, Minnesota has a water quality grade of C (Fair). 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.
- Clarity
- 6.2 ft
- Typical in August
- 73°F
- Max depth
- 28 ft
- Area
- 2,711 acres
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 23
- Open water
- 213 days
Next lake in Beltrami County
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. Water quality is graded C based on 2 sampling years through 2025. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyModerate
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Murky, only visible to about 6.2 ft. Phosphorus level: 34 µg/L. Chlorophyll-a: 12.3 µg/L. Trophic State Index: 54.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6.2 ft | Not graded |
| Phosphorus | 34 µg/L | Fair |
| Chlorophyll-a (Algae) | 12.3 µg/L | Fair |
| Trophic State Index (TSI) | 54 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay 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.
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Water Temperature
Blackduck Lake typically sits around 73°F at the surface in August. 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.
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 28 ft |
| Surface Area | 2,711 acres |
| Shoreline Length | 13.4 mi |
| Littoral Zone | 51% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Blackduck Lake (East)Public
- Blackduck Lake (West)Public
Fish Species
Click a species to see every graded 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.
DNR Fisheries Survey Summary
12 surveys on file from MN DNR Fisheries. Most recent: 2025-08-21 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 32.28 | 0.19 lb |
| CNM | 14.43 | — |
| BKF | 12.59 | — |
| Walleye | 10.42 | 1.97 lb |
| IOD | 3.53 | — |
| Northern Pike | 3.22 | 1.97 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.
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
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.001 m/yr | 6 |
| Phosphorus | ↑ Improving | -3.01 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.97 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (86 observations).
Estimated open water season: 213 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2012-03-26 (2012) | 2013-05-15 (2013) |
| Ice-In | 2019-11-08 (2019) | 2016-12-09 (2016) |
Most recent ice-out: 2023-05-05
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN04-0069-00 · Official waterbody report
County Ranking
Ranked #69 of 85 lakes in Beltrami County
Nearby Lakes With Higher Grades
Blackduck Lake holds Grade C. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Beltrami County
Frequently asked questions about Blackduck Lake
What is the water quality grade for Blackduck Lake?
- Blackduck Lake in Beltrami County, Minnesota has a water quality grade of C (Fair). 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?
- Generally safe for swimming, moderate water quality. Blackduck Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 12.3 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Blackduck Lake?
- Blackduck Lake typically sits around 73°F at the surface in August, 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.
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.
Explore Blackduck Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
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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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated 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