Island Lake
Oneida County, Wisconsin305 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Island Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- 2 aquatic invasives
- 26 ft max depth
- Limited data
Island Lake in Oneida County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 7 ft visibility. Phosphorus: 21.5 µg/L. Maximum depth: 26 ft. Surface area: 305 acres.
Wisconsin DNR rates Walleye as abundant on Island Lake. DNR survey details →
Island Lake is a 305-acre mesotrophic lake in Oneida County, Wisconsin with a maximum depth of 26 feet. The lake supports 6 documented fish species including Musky, Panfish, and Largemouth Bass. Compared to the 66 other monitored lakes in Oneida County, Island Lake ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-23. Methodology: how these readings are compared.
What Island Lake is good for
From access and monitoring records, not editorial picks.
- Fishing6 species recorded
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. Island Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Whether Island Lake is safe to swim in today is a call for the Wisconsin Department of Natural Resources 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 Wisconsin DNR 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.
Moderate clarity, visible to about 7 ft. Phosphorus 21.5 µg/L. TSI 49.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7ft | 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) | 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. | 49 | 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 39°F at the surface in November. Summer average is about 63°F. Usually warmest in Jul (about 63°F) and coldest in Feb (about 37°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (37°F) to its warmest (63°F).
Typical surface water temperature by month, from 11 field readings (2025–2026) 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 2, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Wisconsin DNR rates Walleye as abundant on 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 7 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1979. 1 station on file (most recent sample 2026).
Fish Species (DNR-rated)
Lake Details
Max depth
26 ft
Surface area
305 acres
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Stays near Island Lake
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Top-rated places to stay near Island Lake
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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
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: Stable
Based on 7 years of monitoring (2020–2026).
Water clarity
Stable7 years
Phosphorus
Stable0 µg/L/yr2 years
EPA Impairment Status
Island Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Fish consumption.
Source: EPA ATTAINS assessment unit WI10007314 · Official waterbody report
Nearby Lakes in Oneida County
Frequently asked questions about Island Lake
Where is Island Lake?
- Island Lake is a lake in Oneida County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Island Lake?
- Island Lake in Oneida County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 7 ft visibility. Phosphorus: 21.5 µg/L. Maximum depth: 26 ft. Surface area: 305 acres.
Is Island Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Island Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
What is the water temperature of Island Lake?
- Island Lake typically sits around 39°F at the surface in November, from 11 EPA Water Quality Portal field readings (2025–2026). That is a typical value for the month, not a live reading.
How deep is Island Lake?
- Island Lake has a maximum depth of 26 feet. The lake covers 305 acres.
What fish are in Island Lake?
- Fish species found in Island Lake include Musky, Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Island Lake is located in Oneida County, Wisconsin.
What did the DNR fisheries survey find at Island Lake?
- Wisconsin DNR rates Walleye as abundant on 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 7 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
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 Wisconsin's current advisory before swimming.
Explore Island Lake across LakeQuality
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Where this data comes from
43 measurements from 1 monitoring station, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX43 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
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
Fish and recreation data from Wisconsin DNR Lakes