Determining highest-risk vectors of spiny waterflea spread

Spiny water flea are an invasive zooplankton that pose a serious threat to the ecology and recreational value of Minnesota’s waters. Previous studies have shown that over 40% of northern Minnesota lakes provide suitable habitat for spiny water flea, and human recreational activity is believed to be the primary vector of spread. However, little is known about the specific pathways by which dispersal occurs. This can lead to unclear messaging and directions for recreationalists to prevent further spread.

To learn more about spread and prioritize prevention efforts, researchers will measure the relative risk of spiny water flea attachment on commonly used recreational equipment including anchor ropes, angling lines, bait buckets, downrigger cables, and live wells. Researchers will sample in the morning and the evening to account for spiny water fleas’ tendency to migrate closer to the water’s surface at dusk.

Researchers will rank the threat of each type of gear measured, based on both times of day. This specific information will help recreationalists prioritize their cleaning efforts in order to prevent further spread of spiny water fleas. Results will be disseminated through a marketing campaign in coordination with Minnesota Sea Grant.


All fieldwork has been completed for this project. Researchers conducted seven sampling events on Lake Mille Lacs, which resulted in 718 samples. Researchers deployed commonly used forms of recreational equipment including anchor ropes, angling lines, bait buckets, downrigger cables, and live wells, during daylight and twilight. They cleaned them and then compared the total number of spiny water flea relative to the natural abundance of the fleas in surrounding Mille Lacs lake water. Analyzing this data is currently underway and will allow researchers to create a ranking of the threat that each type of gear poses for spiny water flea spread to other water bodies.

As of July 2019, all samples collected were counted and aged. In total, researchers processed 360 zooplankton tows; 36 braided nylon, 36 twisted nylon, and 36 polypropylene anchor ropes; 35 bait bucket samples; 21 livewell samples; 36 downrigger steel cable samples; 35 downrigger monofilament lines;  and 36 braided, 36 monofilament, and 35 fluorocarbon fishing lines. We are currently crafting and testing our outreach message for distribution in the spring of 2020.

Inside look

What does sampling lakes for spiny water flea look like? Find out in this video!

Project manager: Valerie Brady

Funded by: St. Louis County; Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources

Project start date: 2017

Estimated project end date: 2020

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