Aug 1



This note from Emily Heald, Water Program Coordinator at the Discovery Center:


Hi everyone,

Last week a researcher from UW Madison pulled up a plankton sample from Plum Lake that contained 2 live spiny waterfleas. This has been verified by the DNR. 


At this time, densities are thought to be low, but the lake will require further monitoring. 

Spiny waterfleas are a type of invasive zooplankton that reproduce asexually, so only 1 individual is needed to start a new population. Spiny waterfleas also lay resting eggs in the fall, which are contained in lake sediment. They are very durable. The resting eggs are often the problem, because many lake users do not know to keep mud off anchors and equipment while moving from lake to lake.


It is difficult to say how long spiny waterfleas have been in Plum Lake. Because they are only a quarter of an inch in size, and translucent, finding them can be like finding a needle in a haystack. It makes sense to expect a lag time between when an invasive species such as spiny waterflea establishes until it is detected. 


Spiny waterflea is only in 11 inland Wisconsin lakes. In Vilas: Trout (2014), Star (2013), Stormy (2007), Ike Walton (2015), and Butternut (2014). They are also in the Gile Flowage (2003) in Iron County and the Madison Chain of Lakes in Dane County (2009). Spiny waterfleas eat native zooplankton that graze on algae, and can therefore change food web dynamics in lakes. If the algae-eaters decline, more algae is expected. Lake Mendota in Madison has seen a loss of nearly 3 feet in water clarity that has been attributed to spiny waterflea. 

There is currently no known method to control spiny waterflea. Prevention and education are key. Per Wisconsin law, boaters are required to inspect boats and equipment for plants and animals, remove what they find, drain all water, and never move live fish. While not required by state law, letting your boat dry for at least 6 hours will effectively kill adult and resting egg spiny waterfleas. 

If you are certified to be a Clean Boats, Clean Waters watercraft inspector, I urge you to volunteer at your local boat landings to spread the word about invasive species. If you or a group of your members would like to be trained, please let me know and we can find a time to do so.

Please let me know if you have any questions.

For more information, please stay tuned for the press release to be published by Cathy Higley, Lakes Conservationist for Vilas County. You are also welcome to contact Cathy at 715-479-3738 or

Please also share this important new with your lake associations.

To contact the TLCA,  please email us here.