Island Lake
Cass County, Minnesota358 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Island Lake. Here is what has been measured.
- Mesotrophic
- 45 ft max depth
- Public access
- Limited data
Island Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 15.5 ft visibility. Phosphorus: 21.5 µg/L. Chlorophyll-a (algae): 2.6 µg/L. Maximum depth: 45 ft. Surface area: 358.3 acres.
Minnesota DNR's Standard Survey on August 1, 2022 caught 1.00 walleye per gill net at Island Lake. DNR survey details →
Island Lake is a 358-acre mesotrophic lake in Cass County, Minnesota with a maximum depth of 45 feet. Overall water quality is improving over recent sampling years. The lake supports 12 documented fish species including black crappie, bluegill, and bowfin (dogfish). Public access is available with 1 public boat landing. Compared to the 103 other monitored lakes in Cass County, Island Lake ranks #14 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. Methodology: how these readings are compared.
What Island Lake is good for
From access and monitoring records, not editorial picks.
- Clear water15.5 ft of visibility
- Boat launch1 documented ramp
- Fishing12 species recorded
- Ice seasonIce-out around Apr 15
- Deep water45 ft surveyed max depth
Swimming conditions
Readings onlyLimited data
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. Check local advisories before you swim.
Whether Island 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 Island Lake
These are the measurements Minnesota PCA publishes for Island 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 15.5 ft down. Phosphorus 21.5 µg/L. Chlorophyll-a 2.6 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 15.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 21.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.6µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Island Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Island Lake typically sits around 59°F at the surface in October. Summer average is about 66°F. Usually warmest in Aug (about 68°F) and coldest in May (about 52°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (52°F) to its warmest (68°F).
Typical surface water temperature by month, from 118 field readings (2010–2025) via the EPA Water Quality Portal. See the full Island Lake water temperature breakdown →
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 high (293,765 cells/mL) on May 9, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Standard Survey on August 1, 2022 caught 1.00 walleye per gill net at Island Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Island 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
6 surveys on file from MN DNR Fisheries. Most recent: 2022-08-01 (Standard Survey).
6 surveys on file · most recent 2022-08-01 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 9.23 | 3–9 in 2022-08-01 | 0.16 lb |
| Yellow Bullhead | 3.87 | 5–14 in 2022-08-01 | 0.56 lb |
| Northern Pike | 3.87 | 10–34 in 2022-08-01 | 1.24 lb |
| Largemouth Bass | 3.42 | 5–16 in 2022-08-01 | 1.2 lb |
| Black Crappie | 3.04 | 4–13 in 2022-08-01 | 0.45 lb |
| Rock Bass | 1.12 | 7–10 in 2022-08-01 | 0.49 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.
Bluegill
Yellow Bullhead
Northern Pike
Largemouth Bass
From the 2022-08-01 survey
Island Lake is a 358-acre lake with 5.8 miles of shoreline and a maximum depth of 45 feet located southeast of Longville, MN. A county owned public access is located on the west shore. The DNR has classified Minnesota's lakes into 43 different classes based on physical, chemical and other characteristics. Island Lake…
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 (1570)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
Lake Details
Max depth
45 ft
Surface area
358 acres
Shoreline
5.8 mi
Littoral zone
17%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
6 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,339 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Island LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Island Lake
Compare lakeside cabins, hotels, and vacation rentals near Island Lake in Cass 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 Island 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 →
Follow Island Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Island Lake
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Improving6 years
Ice season
Typical ice-out
Apr 15
Earliest Apr 10, 2005 · Latest May 6, 2022
Typical ice-in
Dec 2
Earliest Nov 26, 2021 · Latest Dec 4, 2024
Most recent ice-out
May 6
2022
8 observations · Minnesota PCA ice records
Nearby Lakes in Cass County
Frequently asked questions about Island Lake
Where is Island Lake?
- Island Lake is a lake in Cass County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Island Lake?
- Island Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 15.5 ft visibility. Phosphorus: 21.5 µg/L. Chlorophyll-a (algae): 2.6 µg/L. Maximum depth: 45 ft. Surface area: 358.3 acres.
Is Island 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 Island Lake?
- Island Lake typically sits around 59°F at the surface in October, from 118 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Island Lake?
- Island Lake has a maximum depth of 45 feet. The lake covers 358.3 acres.
What fish are in Island Lake?
- Fish species found in Island Lake include black crappie, bluegill, bowfin (dogfish), brown bullhead, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, walleye, yellow bullhead. Island Lake is located in Cass County, Minnesota.
What did the DNR fisheries survey find at Island Lake?
- Minnesota DNR's Standard Survey on August 1, 2022 caught 1.00 walleye per gill net at Island Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Island 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 Island Lake thaw?
- Island Lake typically has ice-out around Apr 15. Ice typically forms around Dec 2. The open water season is approximately 231 days.
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 high (293,765 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.
Can I fish at Island Lake?
- Island Lake has 1 documented boat landing 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 Island Lake across LakeQuality
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Where this data comes from
101 measurements from 2 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA101 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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 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