Island Lake
Island Lake in Mahnomen County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 4.5 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 34.3 µg/L. Maximum depth: 43 ft. Surface area: 616.07 acres.
- Clarity
- 4.5 ft
- Max depth
- 43 ft
- Area
- 616 acres
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 30
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Island Lake →
Next lake in Mahnomen County
Island Lake is a 616-acre productive, nutrient-rich eutrophic lake in Mahnomen County, Minnesota with a maximum depth of 43 feet. Water quality is graded F based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. The lake supports 11 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 11 other monitored lakes in Mahnomen County, Island Lake ranks #12 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-30. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyAlgae risk
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.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Murky, only visible to about 4.5 ft. Phosphorus level: 30 µg/L. Chlorophyll-a: 34.3 µg/L. Trophic State Index: 58.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.5 ft | Not graded |
| Phosphorus | 30 µg/L | Fair |
| Chlorophyll-a (Algae) | 34.3 µg/L | Poor |
| Trophic State Index (TSI) | 58 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Island Lake
Compare lakeside cabins, hotels, and vacation rentals near Island Lake in Mahnomen 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Island Lake are listed below.
Top-rated places to stay near Island Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Island Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (57,544 cells/mL) on May 1, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 43 ft |
| Surface Area | 616 acres |
| Shoreline Length | 9.4 mi |
| Littoral Zone | 54% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Island LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Island Lake
DNR Fisheries Survey Summary
13 surveys on file from MN DNR Fisheries. Most recent: 2025-07-21 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 33.25 | 0.16 lb |
| Bluegill | 22.66 | 0.17 lb |
| BNS | 22.25 | — |
| Black Bullhead | 11.31 | 0.49 lb |
| IOD | 10.03 | — |
| Pumpkinseed | 8.66 | 0.12 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
Bluegill
Black Bullhead
Pumpkinseed
From the 2025-07-21 survey
Island Lake is a 616-acre, class-25 lake located in northern Mahnomen County within the boundaries of the White Earth Indian Reservation. The lake sits within the North Central Hardwood Forests ecoregion in the upper reaches of the Wild Rice River Watershed. Island Lake has a littoral area of 331 acres and a heavily…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Island Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — IslandFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Island (0107)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — IslandFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — IslandPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.58 m/yr | 2 |
| Phosphorus | ↑ Improving | -3.5 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -7 µg/L/yr | 2 |
Ice Season
Historical ice data from Minnesota DNR (5 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2015-04-15 (2015) | 2008-04-30 (2008) |
| Ice-In | 2014-11-14 (2014) | 2007-11-22 (2007) |
Most recent ice-out: 2018-04-30
County Ranking
Ranked #12 of 12 lakes in Mahnomen County
Nearby Lakes With Higher Grades
Island Lake holds Grade F. 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 Mahnomen County
Frequently asked questions about Island Lake
What is the water quality grade for Island Lake?
- Island Lake in Mahnomen County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 4.5 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 34.3 µg/L. Maximum depth: 43 ft. Surface area: 616.07 acres.
Is Island Lake safe to swim in?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Island Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 34.3 µg/L. Always check local health department advisories before swimming.
How deep is Island Lake?
- Island Lake has a maximum depth of 43 feet. The lake covers 616.07 acres.
What fish are in Island Lake?
- Fish species found in Island Lake include black bullhead, black crappie, bluegill, brown bullhead, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, walleye, yellow perch. Island Lake is located in Mahnomen County, Minnesota.
When does Island Lake thaw?
- Island Lake typically has ice-out around Apr 30.
Does Island Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Island Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (57,544 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Island Lake?
- Island Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Island Lake. Public access is listed as yes.
Explore Island Lake across LakeGrade
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Fish species and best lakes in Mahnomen County
Species activity outlook by water temperature and season
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High nutrients, frequent algae, reduced clarity
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Where this data comes from
46 measurements from 3 monitoring stations, 2024–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Chippewa Tribe, Minnesota (White Earth Band) (Tribal)
WEARTH_WQX40 samples · 2024 - Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA6 samples · 2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
Monitoring station identifiers (3)
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
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