Didymo and mud snails invade Michigan

| January 17, 2016

The Michigan Department of Natural Resources (DNR) and Michigan Department of Environmental Quality (DEQ) recently received reports and confirmed the presence of New Zealand mud snails and Didymo (Didymosphenia geminata) in Michigan waters.  The confirmed occurrence of these two organisms is of great concern for the State of Michigan’s natural resource agencies because these species have the ability to reach nuisance densities that can cause negative impacts to Michigan’s aquatic ecosystems.

Didymo, commonly called “rock-snot” was detected in June in the St. Marys River near Sault Ste Marie, MI by the Department of Fisheries and Oceans Canada during their annual invasive sea lamprey removal efforts. The detection was later confirmed by the DEQ and Lake Superior State University personnel. Didymo is a type of algae that has previously been identified in the Great Lakes Basin, but this recent detection in the St. Marys River marks the first time that this algae has reached nuisance bloom levels in Michigan waters. In areas where nuisance blooms commonly occur (e.g., western and eastern states) the algae attaches to rocky substrate and covers the bottoms of cold, clean freshwater streams and rivers that recreationally popular trout species generally inhabit. It is debatable whether this species is invasive to MI. Regardless, this is the first bloom ever detected in MI and it is a nuisance species that can negatively impact fishing.

New Zealand mud snails were detected and confirmed more recently in August, 2015 in the Pere Marquette River near Baldwin, MI by DEQ personnel. New Zealand mud snails are an invasive snail that is small in size (1/8” long) and therefore can be difficult to identify. Similar to most other invasive species, New Zealand mud snails reproduce in massive quantities and are extremely resilient (can live out of water for up to 24 hr). Where established, these snails dominate the bottoms of rivers and streams and exhibit invasive qualities, outcompeting and displacing macroinvertebrates that are vital as food sources for many fish species. In addition, these invasive snails have no nutritional value for fish.

The introductions of both Didymo and New Zealand mud snails have been linked to recreational uses, such as angling. These two organisms have the ability to hitch-hike rides on recreational gear, especially waders, which can then be transported to uninvaded waterbodies if disinfection approaches are not taken between locations. This highlights the importance to take steps to inspect and disinfect gear to protect Michigan’s waters and their world-class fisheries.

The DNR and DEQ have begun to communicate and partner with local stakeholder groups on steps moving forward in an attempt to limit the spread of harmful invaders. Unfortunately, control options for these nuisance organisms are limited and have low effectiveness; therefore, outreach targeted at prevention measures are the most effective management tool.  In 2014, the DNR-Fisheries Division initiated conversations with trout angling groups to construct and maintain wader washing stations to promote prevention and outreach for aquatic invasive species. To date, multiple wader wash stations have been constructed and are being maintained on the Au Sable River near Grayling, MI. The plan moving forward is to increase the number of these wader washing stations in Baldwin, MI and adjacent areas. Furthermore, the DNR and DEQ continue to increase outreach campaigns to promote prevention actions such as cleaning, draining, and drying all gear and equipment before and after use in lakes, rivers, and streams. In addition to outreach activities, the DNR and DEQ plan to increase survey efforts to determine the status and distribution of these two organisms.

For further information or questions please contact:

Seth Herbst
Aquatic Invasive Species Coordinator
Michigan DNR-Fisheries Division

Bill Keiper
Aquatic Invasive Species Biologist
Michigan DEQ-Water Resources Division

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Category: Conservation News Posts

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