Spiny Waterfleas: What are they and Where do they Come From?

Q: What are spiny waterfleas and what impacts do they have on the states aquatic resources?

A. Spiny waterfleas are zooplankton (microscopic animals) that are native to Europe and Asia and were introduced into the Great Lakes by ballast water discharged from ocean-going ships.

They eat small animals (zooplankton), including Daphnia, which are an important food for native fishes. In some lakes, they caused the decline or elimination of some species of native zooplankton. Although the spiny water flea can fall prey to fish, its spine seems to frustrate most small fish, which tend to experience great difficulty swallowing the animal.

Spiny waterfleas can spread by attaching to fishing lines, downriggers, anchor ropes and fishing nets, and can be unintentionally transported in bilge water, bait buckets or livewells.

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Christine Herwig, Northwest Region invasive species specialist