Spiny Waterflea

The Spiny Waterflea (Bythotrephes longimanus) is crustaceous zooplankton of the suborder Cladocera. It is native to freshwater lakes in northern Europe and Asia. Both in their native range and throughout the regions in which they have been introduced, the spiny water flea prefers large, deep lakes whose benthic zones have relatively low summer temperatures. Nevertheless, they can also be found in shallower lakes, as well as rivers.

They were introduced into the Great Lakes by the discharge of ballast water from ocean-traveling ships and were first discovered in Lake Ontario in the early 1980s. Local dispersal methods of the spiny water flea include swimming between continuous bodies of water and being moved via anglers and recreational boaters to inland lakes.


Spiny waterfleas disrupt the food web by preying upon zooplankton— particularly daphnia. Being an important food source for juvenile native fish,  loss of zooplankton may result in reduced growth sizes in fish like perch and walleye. Water clarity may also be reduced due to the loss of zooplankton.


Spiny water flea prefers deep lakes but can be found in shallow lakes and rivers. They can collect in globs on fishing lines and downrigger cables. It is distributed in freshwater sources throughout the northeastern United States. It was found in Lake Huron in 1984, Lake Ontario and Lake Erie in 1985, Lake Michigan in 1986, and Lake Superior in 1987.


Spinywater fleaa have a hard outer shell. The species’ most noticeable feature, however, is its long tail spine. The spine makes up 70% of its total body length and contains 1-4 pairs of thorn-like barbs. Their head consists primarily of a single, large eye and a pair of mandibles. The spiny water flea has four pairs of legs, the first pair being considerably longer than the others.

The spiny water flea shares its large tail spine characteristic with a confamilial (shared taxonomic family origin), the fishhook water flea (Cercopagis pengoi). To differentiate these two water fleas apart compare their body sizes and the terminal shape of their tail spines. The spiny water flea is much larger than its fishhook relative and possesses a more robust spine. Additionally, as its name suggests, the end of the fishhook waterflea’s tail spine has a fishhook-shaped curve, which is not found on the spiny water flea. The spiny water flea can reach body lengths of up to 15 m

Control and Management

Physical Control: Clean all aquatic equipment with either high pressured (>250 psi) or hot (>122°F) water after each use in bodies of water containing spiny water flea as a part of regular equipment maintenance.

Use fishing lines designed specifically to prevent the spread of water fleas (ex. the Flea Flicker brand), which has been shown to significantly reduce the fouling of fishing lines by these organisms.

Biological Control: Although spiny water fleas are eaten by numerous species of fish—yellow perch, walleye, white bass, alewife, bloater chub, chinook salmon, emerald shiner, spot-tail shiner, rainbow smelt, lake herring, lake whitefish, and deepwater sculpin—their long, unique spines make them quite difficult to swallow when preyed upon by smaller individuals. So there are no known effective biological control methods at this time.

Photo Credits: 

Title photo: Title photo, MN Aquatic Invasive Species Research Center and the Lake George Association. Fishhook vs spiny water flea photo: (www.protectyourwaters.net).

In the Media: 

New invasive species found in Oneida Lake, described as ‘one of the more disruptive’ pests


“Bythotrephes Longimanus (crustacean).” Global Invasive Species Database. Ed. Richard P. Barbiero. N.p., 10 Aug. 2005. Web. <http://www.issg.org/database/species/ecology.asp?si=151&fr=1&sts=sss&lang=EN>.

“Harmful Aquatic Hitchhikers: Crustaceans: Spiny Water Flea and Fishhook Water Flea.” Protect Your Waters. N.p., n.d. Web. <http://www.protectyourwaters.net/hitchhikers/crustaceans_spiny_water_flea.php>.

Liebig, J., A. Benson, J. Larson, T. H. Makled, and A. Fusaro. “Bythotrephes Longimanus.” NAS – Nonindigenous Aquatic Species. USGS, 4 June 2013. Web. <http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=162>.

“Prevent the Spread of Aquatic Invasive Species.” New York State Department of Environmental Conservation. N.p., n.d. Web. <http://www.dec.ny.gov/animals/48221.html>.

“Spiny Waterflea (Bythotrephes Longimanus).” Minnesota Department of Natural Resources. N.p., n.d. Web. <http://dnr.state.mn.us/invasives/aquaticanimals/spinywaterflea/index.html>.

“Spiny Waterflea (Bythotrephes Longimanus) – FactSheet.” USGS.gov. United States Geological Survey, 17 June 2015. Web. 03 Aug. 2015. <http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=162>.

Prevent the introduction of invasive species into the SLELO PRISM.

Rapidly detect new and recent invaders and eliminate all individuals within a specific area.

Share resources, including funding personnel, equipment, information, and expertise.

Collect, utilize, and share information regarding surveys, infestations, control methods, monitoring, and research.

Control invasive species infestations by using best management practices, methods and techniques to include: ERADICATION (which is to eliminate all individuals and the seed bank from an area), CONTAINMENT (which is reducing the spread of established infestations from entering an uninfested area) and SUPPRESSION which is to reduce the density but not necessarily the total infested area.

Develop and implement effective restoration methods for areas that have been degraded by invasive species and where suppression or control has taken place.

Increase public awareness and understanding of invasive species.

Develop and implement innovative technologies that help us to better understand, visualize, alleviate or manage invasive species and their impacts or that serve to strengthen ecosystem function and/or processes.

Rob Williams                              rwilliams@tnc.org                     Program Director

Megan Pistolese megan.pistolese@tnc.org
Outreach and Education

Brittney Rogers brittney.rogers@tnc.org 
Aquatic Invasive Species

Robert Smith       robert.l.smith@tnc.org 
Terrestrial Invasive Species

Zachary Simek    zachary.simek@TNC.ORG     Conservation and GIS Analyst

During this time the best way to contact our team is via email.