Clamshell Lake
Clamshell Lake in Crow Wing County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15.1 ft visibility. Phosphorus: 16 µg/L. Chlorophyll-a (algae): 2.7 µg/L. Maximum depth: 44 ft. Surface area: 211.06 acres.
- Clarity
- 15.1 ft
- Typical in August
- 65°F
- Max depth
- 44 ft
- Area
- 211 acres
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in Crow Wing County
Clamshell Lake is a 211-acre mesotrophic lake in Crow Wing County, Minnesota with a maximum depth of 44 feet. Water quality is graded A based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 18 documented fish species including black crappie, bluegill, and bowfin (dogfish). Public access is available with 1 public boat landing. Compared to the 84 other monitored lakes in Crow Wing County, Clamshell Lake ranks #50 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-14. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Crystal clear, you can see 15.1 ft down. Phosphorus level: 16 µg/L. Chlorophyll-a: 2.7 µg/L. Trophic State Index: 41.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.1 ft | Not graded |
| Phosphorus | 16 µg/L | Good |
| Chlorophyll-a (Algae) | 2.7 µg/L | Good |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Clamshell Lake
Compare lakeside cabins, hotels, and vacation rentals near Clamshell Lake in Crow Wing 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.
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Water Temperature
Clamshell Lake typically sits around 65°F at the surface in August. Summer average is about 64°F. Usually warmest in Aug (about 65°F) and coldest in May (about 58°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 203 field readings (2017–2025) via the EPA Water Quality Portal. See the full Clamshell Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 44 ft |
| Surface Area | 211 acres |
| Shoreline Length | 6.5 mi |
| Littoral Zone | 67% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Clamshell LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Clamshell 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.
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2024-08-05 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 22.08 | 0.13 lb |
| BCS | 11.18 | — |
| CNM | 7.06 | — |
| Largemouth Bass | 5.69 | 0.92 lb |
| Green Sunfish | 5.61 | 0.1 lb |
| Yellow Bass | 5.60 | 0.44 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
Green Sunfish
Yellow Bass
From the 2024-08-05 survey
Temperature and dissolved oxygen profiles were collected in the deepest basin in Clamshell Lake on August 14, 2024, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Whitefish, the most sensitive coldwater species present in this lake (Cisco are also present).…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Clamshell Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — ClamshellFisheries Lake Survey · MN DNR LakeFinder
- —Public Water Access Sites — ClamshellPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.104 m/yr | 6 |
| Phosphorus | ↓ Declining | +0.76 µg/L/yr | 6 |
| Chlorophyll-a | → Stable | +0.01 µg/L/yr | 6 |
EPA Impairment Status
Clamshell Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN18-0310-00 · Official waterbody report · Matched by proximity (2.53 km)
County Ranking
Ranked #50 of 85 lakes in Crow Wing County
Nearby Lakes in Crow Wing County
Frequently asked questions about Clamshell Lake
What is the water quality grade for Clamshell Lake?
- Clamshell Lake in Crow Wing County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15.1 ft visibility. Phosphorus: 16 µg/L. Chlorophyll-a (algae): 2.7 µg/L. Maximum depth: 44 ft. Surface area: 211.06 acres.
Is Clamshell Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Clamshell Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.7 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Clamshell Lake?
- Clamshell Lake typically sits around 65°F at the surface in August, from 203 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Clamshell Lake?
- Clamshell Lake has a maximum depth of 44 feet. The lake covers 211.06 acres.
What fish are in Clamshell Lake?
- Fish species found in Clamshell Lake include black crappie, bluegill, bowfin (dogfish), brown bullhead, green sunfish, hybrid sunfish, lake whitefish, largemouth bass, northern pike, northern sunfish, pumpkinseed, rock bass, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Clamshell Lake is located in Crow Wing County, Minnesota.
Are there boat ramps on Clamshell Lake?
- Clamshell Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Clamshell Lake. Public access is listed as yes.
Explore Clamshell Lake across LakeGrade
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Where this data comes from
108 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA108 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory