Shag Lake
Marquette County, Michigan193 acresView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Impaired · Mercury
- 30 ft max depth
- Public access
- Limited data
Shag Lake in Marquette County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 15.3 ft visibility. Maximum depth: 30 ft. Surface area: 192.7 acres.
- Clarity
- 15.3 ft
- Max depth
- 30 ft
- Area
- 193 acres
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Shag Lake’s letter
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Free interactive depth-contour map of Shag Lake, reaching a maximum surveyed depth of 30 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Michigan DNR.
Why Shag Lake has no grade
Shag Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Shag Lake is Not Rated — not an F. Its 15.3-foot median from 10 readings collected 2022–2023 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by EGLE and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Shag Lake is a 193-acre lake in Marquette County, Michigan with a maximum depth of 30 feet. Overall water quality is improving over recent sampling years. The lake supports 7 documented fish species including Blacknose shiner, Golden shiner, and Iowa darter. Public access is available.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2023-05-31. Grade methodology: LakeQuality methodology.
What Shag Lake is good for
From access and monitoring records, not editorial picks.
- Clear water15.3 ft of visibility
- Fishing7 species recorded
- Deep water30 ft surveyed max depth
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Shag Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Water quality measurements for Shag Lake
These readings exist but are not enough for an A–F grade — see why.
Crystal clear, you can see 15.3 ft down. TSI 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.3 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 30 ft |
| Surface Area | 193 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Shag Lake
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +3.59 m/yr | 2 |
EPA Impairment Status
Shag 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 MI040301100206-02 · Official waterbody report
Graded lakes near Shag Lake
Shag Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Marquette County
Frequently asked questions about Shag Lake
Where is Shag Lake?
- Shag Lake is a lake in Marquette County, Michigan. LakeQuality has not rated this lake (UNRATED) — the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity.
What is the water quality grade for Shag Lake?
- Shag Lake in Marquette County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 15.3 ft visibility. Maximum depth: 30 ft. Surface area: 192.7 acres.
Is Shag Lake safe to swim in?
- The letter is not a swimming clearance. Shag Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is Shag Lake?
- Shag Lake has a maximum depth of 30 feet. The lake covers 192.7 acres.
What fish are in Shag Lake?
- Fish species found in Shag Lake include Blacknose shiner, Golden shiner, Iowa darter, Mimic shiner, Northern redbelly dace, White sucker, Yellow perch. Shag Lake is located in Marquette County, Michigan.
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Where this data comes from
10 measurements from 1 monitoring station, 2022–2023. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- North American Lake Management Society
NALMS10 samples · 2022–2023
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)