Trease Lake
Trease Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 4.7 ft visibility. Phosphorus: 29 µg/L. Chlorophyll-a (algae): 8.2 µg/L. Surface area: 96.85 acres.
- Clarity
- 4.7 ft
- Area
- 97 acres
- Trend
- ↑ Improving
- Public access
- No
Next lake in St. Louis County
Why Trease Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Trease Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Trease Lake is a 97-acre lake in St. Louis County, Minnesota. Overall water quality is improving over recent sampling years. The lake supports 4 documented fish species including largemouth bass, northern pike, and smallmouth bass. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-07-28. Grade methodology: LakeGrade methodology.
Watch Trease Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Trease Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Murky, only visible to about 4.7 ft. Phosphorus level: 29 µg/L. Chlorophyll-a: 8.2 µg/L. Trophic State Index: 53.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.7 ft | Not graded |
| Phosphorus | 29 µg/L | Not graded |
| Chlorophyll-a (Algae) | 8.2 µg/L | Not graded |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Trease Lake
Compare lakeside cabins, hotels, and vacation rentals near Trease Lake in St. Louis 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 Trease 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 →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 97 acres |
| Shoreline Length | 4.8 mi |
| Public Access | No |
No bathymetric survey has been published for Trease Lake, so its depth is not documented here.
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Trease Lake
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 2014-09-02 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Northern Pike | 3.17 | 2.01 lb |
| Smallmouth Bass | 1.33 | 0.53 lb |
| Largemouth Bass | 1.00 | 1.03 lb |
| White Sucker | 0.33 | 3.03 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.
Northern Pike
Smallmouth Bass
Largemouth Bass
White Sucker
From the 2014-09-02 survey
Erickson Lake is located approximately 10 miles N of Ely and is entirely within the BWCAW. Lake levels at the time of the assessment were approximately 1.5 feet below average and the shoreline was defined by woody debris with exposed boulders and muck. Access is by a 180 rod portage from North Hegman Lake. There are 3…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Trease Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — EricksonFisheries Lake Survey · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.18 m/yr | 2 |
Graded lakes near Trease Lake
Trease Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in St. Louis County
Frequently asked questions about Trease Lake
What is the water quality grade for Trease Lake?
- Trease Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 4.7 ft visibility. Phosphorus: 29 µg/L. Chlorophyll-a (algae): 8.2 µg/L. Surface area: 96.85 acres.
Is Trease Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Trease Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Algae concentration (chlorophyll-a) is 8.2 µg/L. Always check local health department advisories before swimming.
What fish are in Trease Lake?
- Fish species found in Trease Lake include largemouth bass, northern pike, smallmouth bass, white sucker. Trease Lake is located in St. Louis County, Minnesota.
Explore Trease Lake across LakeGrade
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in St. Louis County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Lake Vermilion Area area
Where to stay at Minnesota's top lakes, each with its grade
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Lakes in the Rainy Lake Watershed, ranked by water quality
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
State Parks Near Trease Lake
Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
5 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA5 samples · 2022
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 2130 B ~ Nephelometric Method
- 2120 B ~ Color in Water by Visual Comparison
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
Lake details from Minnesota DNR LakeFinder