Long Lake
Cass County, MinnesotaLimited DataOligotrophic
Long Lake earns an A — every scored parameter (clarity) rates among the best monitored waters in Cass County.
A TSI value of 36 puts Long Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. A maximum depth of 37 ft puts Long Lake in the middle of Minnesota's depth distribution. The lake's 246 acres and 5.1 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Within Cass County's 132 graded waters, Long Lake sits at rank 4, near the top of the local distribution.
No invasive species are currently listed at Long Lake — the lake remains off the Minnesota infested-waters roster. Walleye are documented at Long Lake, one of 12 fish species on record for the lake. A documented public access point at Long Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-27. Grade methodology: LakeGrade methodology.
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 16.8 ft down. Trophic State Index: 36.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16.8 ft | A |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 37 ft |
| Surface Area | 246.3 acres |
| Shoreline Length | 5.1 mi |
| Littoral Zone | 57% |
| Public Access | Yes |
Fish Species
Click a species to see all Minnesota and Wisconsin lakes where it is found.
→ Best fishing times for Long Lake (14-day solunar calendar)
→ Is it safe to eat fish from Long Lake? (mercury & PFAS guide)
→ Long Lake fishing regulations (limits, seasons, special rules)
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.076 m/yr | 5 |
| Phosphorus | → Stable | 0 µg/L/yr | 5 |
Location
County Ranking
Ranked #4 of 132 lakes in Cass County
Nearby Lakes in Cass County
More Minnesota Lake Rankings
Other Grade A Lakes in Minnesota
Oligotrophic Lakes in Minnesota
DNR Fisheries Survey Summary
7 surveys on file from MN DNR Fisheries. Most recent: 2024-06-24 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 22.61 | 0.16 lb |
| Bluntnose Minnow | 17.47 | — |
| Largemouth Bass | 9.39 | 0.86 lb |
| Black Crappie | 6.04 | 0.37 lb |
| Northern Pike | 4.56 | 1.61 lb |
| Yellow Bass | 4.40 | 0.56 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.
Bluegill
Largemouth Bass
Black Crappie
Northern Pike
From the 2024-06-24 survey
A targeted survey of nearshore fish species in Long Lake was conducted on June 25-26, 2024 by Index of Biological Integrity (IBI) Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine. Backpack electrofishing was…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Long Lake. 3 reports on file.
- —Fisheries Lake Survey — LongFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Long (1611)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — LongPublic Water Access Sites · MN DNR LakeFinder
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Lake details from Minnesota DNR LakeFinder
Most recent sample: 2024-09-27
Monitoring stations: 1