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Spiny Waterflea

Photo by Dave Brenner, Michigan Sea Grant College Program

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Common Name: Spiny waterflea
Scientific Name: Bythotrephes cederstroemi
Origin: Eurasia


Spiny waterfleas are tiny crustaceans less than 1/2″ long with long, sharp, barbed tails. Spiny waterfleas collect in gelatinous globs on fishing equipment and lines.


Spiny waterfleas thrive in deep lakes but can also be found in shallow lakes and rivers.


Spiny waterfleas are voracious predators of small zooplankton, like Daphnia, an important food for young native fishes. They reproduce rapidly and eggs are capable of lying dormant all winter, resisting drying and freezing. As a result of their sharp spines, smaller fish cannot readily consume them, adding to their explosive populations.


No control methods exist. Prevention is key. Since fishing and boating equipment is the most likely means of spread, anglers and water-users must take precautions. Boats and gear should be thoroughly checked, cleaned, and dried before entering new waterways.

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