Fishhook waterflea

Scientific Name: Cercopagis pengoi

J. Liebig, NOAA GLERLCopyright Info

Identification: The fishhook waterflea is a small freshwater crustacean. It has a tail three to four times its body length, with three pairs of small hooks near the base and a large hook on the end. This species is a type of zooplankton, which are small animals that live suspended in the water.

Size: The fishhook waterflea body is less than 0.125 inch (1-3 mm) in length, but including the tail, this species can reach 0.25-0.5 inch (6-13 mm) in length.

Native Range: The fishhook waterflea is found in the Black, Caspian, Azov, and Aral seas of Europe and Asia.

Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Cercopagis pengoi are found here.

Full list of USGS occurrences

State/ProvinceYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
Illinois199919991Lake Michigan
Michigan199920045Detroit; Lake Huron; Lake Michigan; Lake Superior; Muskegon
New York199820194Lake Champlain; Lake Erie; Lake Ontario; Seneca
Ohio200120051Lake Erie
Pennsylvania200220021Lake Erie
Wisconsin200020021Lake Michigan

Table last updated 9/30/2019

† Populations may not be currently present.

* HUCs are not listed for areas where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).

Means of Introduction: These organisms were probably introduced to the Great Lakes by transoceanic ships discharging ballast water. Recreational boat traffic and other human activities have spread the species within the Great Lakes and to inland lakes.

Status: This freshwater crustacean was first identified in Lake Ontario in 1998. Since then, established populations have been recorded in Lake Erie, Lake Huron, and Lake Michigan. Individual fishhook waterfleas have been collected from Lake Superior, but it is unclear whether this species has become established there. The fishhook waterflea also inhabits inland lakes, including some in New York and Michigan.

Remarks: The species can live in both freshwater and slightly salty lakes.

Author: Illinois-Indiana Sea Grant

Contributing Agencies:
NOAA Sea Grant GLRI Logo

Revision Date: 9/25/2012

Citation for this information:
Illinois-Indiana Sea Grant, 2019, Fishhook waterflea: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI,, Revision Date: 9/25/2012, Access Date: 10/13/2019

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.