New research from U of M shows how to help stop the spread of spiny water fleas in Minnesota lakes

May 10, 2021


ST. PAUL, Minn. — Based on new research, the Minnesota Aquatic Invasive Species Research Center is asking anglers to wipe fishing lines, reels, bait buckets, and livewells in addition to draining all water from boats and equipment when leaving a spiny water flea-invaded lake in order to ‘Stop Spiny.’

Spiny water fleas, though tiny (roughly the size of a grain of rice) can cause big problems for Minnesota lakes. These invasive zooplankton eat the microscopic food young, native fish need to survive and grow. Previous MAISRC research conducted by Dr. Gretchen Hansen has shown that walleye in lakes invaded by spiny water fleas are smaller and less abundant than walleye in uninvaded lakes. Stopping the spread of spiny water fleas is a crucial step in protecting our lakes; however, until recently, there was little information available on what recreational equipment was likely to collect spiny water fleas on it during use. 

To fill the knowledge gap, MAISRC researchers, Drs. Valerie Brady and Donn Branstrator outfitted two research vessels with fishing equipment to run real-world simulations on spiny water flea-infested lakes in Minnesota. The findings showed that fishing lines were most likely to entangle spiny water fleas, but they also get caught on downrigger cables, bait buckets, and livewells

“What we found is that the more spiny water fleas there are in the lake, the more likely they are to end up on your gear—but in particular, fishing line is what really ensnares spiny water flea,” explained Brady. “However, they can also survive in residual water in your boat, bait bucket, or livewell. We need all anglers to drain their water and then wipe down their gear to help prevent any further spread.”

With Minnesota’s walleye fishing opener days away, anglers should begin to implement the practice of wiping down fishing gear now while keeping in mind that spiny water flea numbers will not peak until mid-summer. Not seeing a spiny water flea on your line this coming weekend doesn’t mean the lake is not (or is no longer) invaded. Most anglers will encounter spiny water fleas in the form of a gelatinous clump stuck in the eyelet of their fishing pole, or gathered on sinkers or lures in late-June through mid-fall. For anglers fishing in invaded lakes—such as Lake Mille Lacs, Island Lake Reservoir, or Lake of the Woods—taking the simple steps of draining water and wiping down gear is critical because treatment once spiny water fleas have invaded is not an option. 

“We don’t currently have any management options available to treat spiny water fleas, whether that be biological, chemical, or physical, short of draining the entire lake. So the best approach to fighting this invasive species is to contain its range and prevent any future spread,” explained Branstrator. 

As part of the project, MAISRC created a campaign called ‘Stop Spiny’ that aims to educate Minnesotans about spiny water fleas, their spread, and how to stop them. Visit to learn more about this project and to see a map of what lakes in Minnesota are already invaded by spiny water fleas.  



Kristin Loobeek, MAISRC Communications Specialist, [email protected]