Seal of Dane County County of Dane
Dane County Land & Water Resources Department

Dane County Works with UW & DNR to Assess Spiny Water Flea Threat to Area Lakes

September 23, 2009
Susan Jones, Watershed Management Coord-608-224-3764 Ron Martin, Dane County AIS Plan author - 608-712-7456 Dr. Jake Vander Zanden, UW- Madison-608-262-9464
Land & Water Resources

Last week the University of Wisconsin announced that undergraduate students in Dr. Jake Vander Zanden’s limnology class discovered spiny water fleas, an aquatic invasive species, in Lake Mendota. They are very abundant in Lake Mendota, and their presence has since been confirmed in Lake Monona and Lake Waubesa through analysis of samples collected in August and September by the UW Center for Limnology.

Spiny water fleas are tiny, predacious crustaceans that threaten aquatic ecosystems and fishing by competing with native fish for food, and by fouling fishing gear. Unfortunately, at this time no effective strategy is available to control spiny water fleas once they are introduced to lakes.Dane County Watershed Management Coordinator Sue Jones said, “We have worked proactively over the years to prevent harm to our aquatic ecosystems by keeping invasive species out of our lakes and streams. The long-term impacts of the newly-discovered water flea are unknown at this time, but we need to take all steps necessary to prevent their spread to other waters.” Ron Martin, lead author of Dane County’s Aquatic Invasive Species Prevention and Control Plan, said: “Their long-term effects can be significant depending on how well the spiny water fleas establish themselves, and must be taken seriously. In other lakes they have reduced the abundance of zooplankton (tiny aquatic animals eaten by fish), and that’s not good for fish or for water quality.” single spiny water flea (photo by US Fish and Wildlife Service) cluster of spiny water fleas on fishing line

Spiny water fleas, first discovered in Lake Ontario in 1982 (having arrived in the US in ships’ ballast water from Eurasia), have spread to all the Great Lakes, inland lakes, and most recently lakes Mendota, Monona and Waubesa. They travel to new lakes with human assistance—fishing gear and in or on boats or other vessels transferred from spiny water flea-contaminated waters. Water fleas collect in masses on fishing lines and downrigger cables. These masses can clog the eyelets of rods, damage a reel’s drag system and prevent fish from being landed.

Dane County education and prevention actions
Dane County’s AIS Plan is available at Dane County staff will continue to promote the Plan’s recommended actions to prevent transport of all aquatic invasive species like spiny water fleas:

· inspect boats, trailers and equipment and remove aquatic plants, animals and mud. Spiny water fleas are small (1/4-5/8 inches total length) and although visible to the naked eye, are difficult to identify without magnification. They appear as gelatinous or cotton batting-like material with black dots on fishing lines, especially where they meet a swivel, lure or downrigger ball connection.
· drain water from boats and all equipment
· don’t move live fish away from a waterbody
· buy minnows from a Wisconsin bait dealer. Use leftover minnows only under certain conditions
· rinse boats and equipment with hot or high-pressure water or dry for at least 5 days

Dane County staff will be adding decals to all the aquatic invasive species signs posted on lakes Mendota, Monona, and Waubesa; to indicate that spiny water fleas are present.

Dane County staff will be working with DNR and the UW Center for Limnology in assessing impacts of spiny water fleas on Lake Mendota and downstream lakes in the Yahara River chain, and the extent of their infestation.

Dane County staff will continue to encourage riparian owners to help track the spread of aquatic invaders by examining their piers and boats for zebra and Quagga mussels, and spiny water fleas, when they remove their equipment from the water this fall. While large adult zebra or Quagga mussels are fairly easy to identify, smaller mussels that have recently attached to a pier or boat will feel like rough sandpaper and be much harder to identify.

Anyone who thinks they may have spotted an invasive species animal should record the exact location; store specimens in rubbing alcohol in a sealed container and contact the local DNR office at (608) 275-3329.