Fish Hook and Spiny Waterfleas

Fish hook and spiny waterfleas have been a problem in Lake Michigan for quite a while. A few years ago, they were found in two water bodies in Vilas County. In 2009 large populations were found in Lake Mendota and Lake Monona in Dane County. We do not want to spread these invasive species to Lake Winnebago or our other inland lakes.

Both waterfleas are only about ¼ to ½ inches in length and individual waterfleas may go unnoticed. However, both species tend to gather in masses on fishing lines and downrigger cables, making them quite messy, so anglers are often the first to discover a new infestation.

Spiny and fishhook waterfleas eat zooplankton, putting them in direct competition with juvenile fish for food. Young fish have trouble eating these waterfleas due to their long, spiny tails.

Fishing, boating, and other water recreational equipment can transport spiny waterfleas and their eggs to new water bodies. Their resting eggs can survive long after the adults are dead. Great care must be taken not to transport water between water bodies and to remove all waterfleas and eggs from all equipment.