Fishhook waterflea

Cercopagis pengoi


Photo credit: USGS

Habitat: estuarine habitats, lakes, marine habitats, water courses, wetlands


Description: This species can only be identified using a microscope. When magnified, a unique loop at the end of its tail, as well as a pointed brood pouch which may contain eggs can be seen. Please see the Global Invasive Species Database for a more detailed description of this species (


Origin and Distribution: Originates in the Caspian, Black and Azov seas and small coastal lakes in this area. Considered invasive in Eastern Europe, Baltic Sea, Laurentian Great Lakes and Finger Lakes.


Impacts: Occurring in estuaries, lakes, water courses, and wetlands. It is a voracious predator and may compete with other invertebrates and vertebrates. Through this competition, C. pengoi has the potential to affect the abundance and condition of fish and fish larvae; this species also impacts fisheries by clogging nets and fishing gears.


How might it get here? The only described vector for this species is ships ballast water.


Prevent Spread:

Bait or bait water should not be released into water body or transport from one water body to another. Good containment measures should be followed to control both the spread of adults and resting eggs, which are capable of surviving desiccation and freezing for periods of several years. 

Invasive Species Ireland

Invasive Species Ireland