U of M research shows how to help stop the spread of spiny waterfleas in Minnesota lakes

May 13, 2021

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 waterflea-invaded lake in order to ‘Stop Spiny.’

Spiny waterfleas, 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 Gretchen Hansen has shown that walleye in lakes invaded by spiny waterfleas are smaller and less abundant than walleye in uninvaded lakes. Stopping the spread of spiny waterfleas 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 waterfleas on it during use.

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

“What we found is that the more spiny waterfleas 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 waterflea,” 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 waterflea numbers will not peak until mid-summer. Not seeing a spiny waterflea on your line this coming weekend doesn’t mean the lake is not (or is no longer) invaded. Most anglers will encounter spiny waterfleas 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 waterfleas have invaded is not an option.

“We don’t currently have any management options available to treat spiny waterfleas, 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 waterfleas, their spread, and how to stop them. Visit StopSpiny.org to learn more about this project and to see a map of what lakes in Minnesota are already invaded by spiny waterfleas.