Invasive Species: Fishhook Waterflea

The fishhook waterflea (Cercopagis pengoi) is pictured at top. The other species is also an invasive

I have been featuring a lot of large-bodied invasive species lately, so this time around I've decided to talk about a far smaller species that still causes a lot of issues. This small crustacean is native to Southern Europe, coming from some small lakes in the area as well as the Black, Azov, and Caspian Seas. Through mainly ballast water, the species has spread to the Baltic Sea waterways all over Easter Europe, along with the Great Lakes and Finger lakes in North America.

Though small, this waterflea is rather formidable. A predatory species, it eats all sorts of native zooplankton and has been linked to large drops in the numbers of many known prey species in its introduced range. It also competes with native species that also eat zooplankton and fouls fishing equipment, nets especially. Fishhook waterfleas also will eat very young fish, particularly those that normally feed on phytoplankton. This can lead to major ecological changes, including changes in upper-level predation and increases in the intensity of algal blooms that occur. It's believed that the trophic changes that these small creatures cause will prove problematic for fish stocks, which, combined with equipment fouling, does not bode well for fisheries. Apparently, there have also been allergic reactions reported in fishermen that handle materials that have become fouled by these animals.

There is currently no known way to kill off these crustaceans, and the only management methods that are being done are really to prevent further spread of the animal. This includes better control of ballast water and regulations on the proper disposal and cleaning of equipment that has been in water known to house populations of the fishhook waterflea.

This species is currently on the list of 100 World's Worst Invasives at #21.  

Image is from Wikimedia Commons and is copyright free.