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Invasive Species: Spiny Waterflea

Spiny Waterflea

(Bythotrephes longimanus)

*Established 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 single, white spiny waterflea against a blue background.

Photo courtesy of Bill O’Neill, University of Wisconsin Sea Grant.

The line on a fishing pole is covered by a mass of spiny waterfleas.

Photo courtesy of Jeff Gunderson, Minnesota Sea Grant.


  • Long, straight tail spine that is twice the length of its body.
  • 1-2 pairs of barbs on the tail spine.
  • Total length: ¼ - ½ inch.

Diet: Diet consists of smaller zooplankton such as small copepods and rotifers.

Habitat: Spiny waterflea can be found among the zooplankton in the upper water column of temperate lakes. They can tolerate brackish water and prefer cooler water temperatures.

Native Range: Northern Europe and Asia.

Local Concern: The spiny waterflea causes major changes in the zooplankton community structure, reproduce rapidly, and compete directly with small fish for food. Additionally, they foul fishing gear when their tail spines get hooked on fishing lines.

Means of Introduction: Most likely introduced to the Great Lakes via ship ballast water, possibly as resting eggs in mud.


Spiny Waterflea Invasive Species Alert - Printable PDF