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Invasive Species: Fishhook Waterflea

Fishhook Waterflea

(Cercopagis pengoi)
*Detected in Michigan*

Report this species:

Use the Midwest Invasive Species Information Network (MISIN) online reporting tool

- Or - download the MISIN smartphone app and report from your phone -


A white to translucent fishhook waterflea with a long tail.

Photo courtesy of Igor Grigorovich, University of Windsor

A fishhook waterflea with a one millimeter scale line to indicate its size.

Photo courtesy of NOAA Great Lakes Environmental Research Laboratory


  • Translucent body with black eyes.
  • Body length: 1-3 mm; 6-13 mm including tail.
  • Tail contains 3 pairs of barbs and an s-shaped hook near the end.
  • Generally in clusters of at least 10 individuals.
  • Clusters appear as wet cotton on items like cables, ropes, and fishing lines.

Diet: Fishhook waterfleas consume other zooplankton species.

Habitat: Fishhook waterfleas live in freshwater and brackish lakes.

Native Range: Aral, Azov, Black, and Caspian seas of Asia and Europe.

U.S. Distribution: The fishhook waterflea has been reported in Lakes Ontario, Michigan, Erie, Huron and Superior; Muskegon Lake and the Finger Lakes of New York.

Local Concern: Dietary preference put this species in direct competition with native planktivores. The long tail spine and barbs make this zooplankton less appealing to planktivorous fish, so population regulation from predation is unlikely to occur. This could have a serious effect on planktivore food supply in the Great Lakes region.

Means of Introduction: Ballast water, recreational boating, fishing equipment.


Fishhook Waterflea Invasive Species Alert - Printable PDF