Ruffe
Invasive SpeciesFound in 10 lakes
Ruffe is documented in 10 lakes across our dataset — 8 in Minnesota and 2 in Wisconsin. Each state's natural-resources agency maintains an official "infested waters" roster that triggers boat-launch decontamination protocols. 10 lakes — narrow enough that aggressive containment is still on the table. Most upper-Midwest invasives that established here did so quietly over a decade before anyone noticed, so a low number today is not a guarantee for tomorrow.
The presence of Ruffe does not directly change a lake's LakeGrade rubric score — the grade measures the water itself, not the species inhabiting it. But invasive presence is a meaningful adjacent signal worth reading alongside the grade.
Lakes with Ruffe
| Lake | County | State | Grade | Depth |
|---|---|---|---|---|
| Superior Lake | Cook | MN | A | - |
| Superior Lake | St. Louis | MN | A | - |
| Little Lake Deep | Cook | MN | B | - |
| Teal Lake Deep | Cook | MN | C | - |
| Duluth Lake | St. Louis | MN | D | - |
| Duluth Lake | Douglas | WI | D | - |
| St. Louis Bay Lake | Douglas | MN | D | - |
| St. Louis River Outlet Upstream of John A. Blatnik Memorial Bridge Lake | Douglas | WI | D | - |
| Little Lake Inlet | Cook | MN | F | - |
| Little Lake Landing | Cook | MN | F | - |
Frequently Asked Questions
How many lakes have ruffe?
Ruffe has been documented in 10 graded lakes: 8 in Minnesota, 2 in Wisconsin.
Does ruffe affect water quality?
Invasive species can significantly affect lake ecosystems. They may alter nutrient cycling, displace native species, and change water clarity. Lakes with ruffe should be monitored for changes in water quality over time.
Invasives Found With Ruffe
Source: EPA National Aquatic Resource Surveys, 2026.