April 23, 2014

Zebra mussels spreading in the Iowa Great Lakes

More zebra mussels are being found this year attached to boat hoists that are being removed from the West Okoboji, East Okoboji and Upper Gar Lakes. Iowa DNR Fisheries Biologist Mike Hawkins says it’s not unexpected given the discovery of zebra mussels in East Okoboji and Upper Gar Lake last fall.

And they’re not isolated to small sections of the lakes. “We’re actually finding them all over,” Hawkins says. He estimates around 90 percent of the hoists in the vicinity of the south end of East Okoboji Lake had zebra mussels on them, while one-quarter of the hoists on West Okoboji Lake had the invasive species attached. “They like the shade…they’ll be attached to rocks on the bottom. And as the infestation develops, they’ll be attached to basically everything that’s hard,” Hawkins says.

The first hoist Hawkins examined this fall had several zebra mussels attached to it. He’s expecting a rapid explosion of the species in the next few years. “They can reach very extreme densities, tens-of-thousands of individuals per square meter,” Hawkins says.

Zebra mussels are plankton feeders, which filter large quantities of water and may actually improve water clarity, but the negatives far outweigh the positives. “They don’t like the blue-green algae, so we may see some increases in blue-green algae blooms on the lakes,” Hawkins says.

There is no known treatment to completely eradicate zebra mussels from the lakes. Hawkins says they will likely significantly alter the ecosystem of waterbodies.

Zebra mussels also attach to water intakes and pipes of power plants and water supply facilities causing damage.

Find out more about zebra mussels here: www.iowadnr.gov/Portals/idnr/uploads/fish/files/ZM%20Fact%20Sheet.pdf

(Reporting by Ryan Long, KICD, Spencer)