The rock glander population continues to be a problem in the Manistee River

Those in the Manistee River may continue to notice brown grime clinging to rocks or trees below the surface.

Didymo, more commonly known as rock snot, is a type of algae that continues to propagate in the upper reaches of the Manistee River. The appearance of rock snot was first reported last fall, but it continues to be a problem. Although usually microscopic, the strands can grow up to six inches thick. Rock snot is not harmful, but it makes swimming and boating difficult and traps sediment that feeds trout.

Didymo is native to northern regions of Europe, Asia and North America in places like Lake Superior and parts of Canada, according to Michigan’s Invasive Species Program. Although cells have been documented in the Great Lakes Basin and Michigan waters in low abundance, their harmful blooms are a recent problem and first appeared in the St. Marys River in 2015.

According to the Michigan State ANR, researchers are still working to determine what triggers the harmful didymo blooms. Scientists believe this could be due to changing environmental conditions, or the spread of didymo into new waterways by fishing gear, which is the common way pest species spread. Didymo can survive for 40 days in cool, dark dam conditions, such as on angling gear, waders, and boots with neoprene and felt soles, according to the Michigan State ANR.

“At the moment didymo is a big headache with a lot of people working to fix it. We need to find out why it is showing up where it is and more importantly how best to decontaminate gear to prevent it from happening. spread,” said Ann Miller, aquatic biologist and avid fly fisherman of the Manistee River. “Right now many local fishing guides are doing their best to avoid the stretch of the Manistee where the didymo blooms but the fishing is their livelihood.”

Three things can be done to prevent the spread:

  • Clean mud, debris and plant matter from boats
  • Drain wells and bait buckets
  • Decontaminate and dry equipment for at least five days before going to another body of water

Other things to keep in mind if you’re fishing in water with a known rock snot population are to plan decontamination time between trips, avoid going to multiple shores in one day, and designate specific gear to be used only in infested water.

For more information on preventing the spread of aquatic invasive species on boating and fishing gear, click here.

To report a rock snot sigh, click here. However, you will need to create a report before you can report your sighting.

You can also report rock snot by emailing the location and photos to [email protected]

About Patricia Kilgore

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