Assessing Our Risks to Prioritize Our Activities

The resources to completely defend Lake Vermilion’s fishery and business community will never be available. We’re committed to deploying the resources we can muster on our highest priority risks as efficiently as we can.

Those high-priority risks have evolved rapidly over the last couple years. In 2016, starry stonewort – a relative newcomer to Minnesota’s AIS roster – was found in 4 new counties and 7 new lakes, including Upper Red, Cass and Winnibigoshish, after its discovery in Lake Koronis in 2015. This grass-like macro algae can produce dense mats, can interfere with recreation, and can alter habitat for young fish. Property values for affected areas of Lake Koronis appear to be significantly depressed according to anecdotal reports, with no buyers stepping forward.

Also in 2016, hybrid watermilfoil made headlines. Little is known about crosses between invasive Eurasian watermilfoil and our native Northern watermilfoil, but anecdotal reports suggest increased invasiveness and evidence of herbicide resistance. In Lake Vermilion, native watermilfoil co-exists with other native vegetation. We have no known Eurasian watermilfoil – an indication our habitat and water chemistry may not be suitable. However, at this point, no one knows whether certain Eurasian x native hybrids may overwhelm our native vegetation.

Starry stonewort and hybrid watermilfoils are major threats and join zebra mussels at the top of Lake Vermilion’s AIS concerns. Our current risk assessment – including what we don’t know – is summarized below:

Species Introduction Risk Habitat Suitability Impact if Population Established
Fishery & Ecosystem Recreational Boating
Zebra mussels Very high Unknown. Limited to calcium hotspots? Serious stressor. Filters zooplankton, limiting growth of fry. Negative but water clarity appeals to some
Starry stonewort Moderate & increasing Unknown. Limited to specific bays? Serious stressor. Unknown impact on each fishery. Severe in bays with suitable habitat
Hybrid and Eurasian watermilfoil High Unknown. Limited to specific bays? Serious stressor. Unknown impact on each fishery. Severe in bays with suitable habitat
Spiny waterfleas Found in Big Bay in 2015 High. Likely to spread beyond east basin. Serious stressor. Consume zooplankton, limiting growth of fry. Low
Curly-leaf pondweed Present in 3 small areas. Moderate/high in specific bays Limited to specific bays with suitable habitat. May become severe in bays with suitable habitat.
Rusty crayfish Present in east basin and west to Niles Bay High for sandy, rocky, rubble bottoms Weed bed destruction impacting several fish species Low/moderate

In addition to the priority threats in the table above, Lake Vermilion is surrounded by a host of other AIS threats which we continually monitor. Examples include quagga mussel, Brazilian waterweed, brittle naiad, and water hyacinth.