Baird, 1857 (water flea)

Habitat: Freshwater ponds and lakes.
Life History: Size 0.6 mm; algae-eating cladoceran; in less populated, homeostatic waters, E. coregoni infrequently reproduces sexually and instead maintains populations by parthenogenic females; maximum populations are found in late June in the US.
Native Range: Eurasia.
Nonindigenous Range: First known occurrence in the US was in 1966 from Lake Michigan; this species has since been introduced to all of the Great Lakes; found in NY in the Delta Reservoir, Blanheim Gilboa Reservoir, Cross Lake, Franklin Falls Pond, Ensign Pond and Snyders Lake; found in 1968 in the Pymatuning Reservoir in Pennsylvania; most recently reported from Lake Champlain, Vermont in 1994.
Impacts: One of the dominant zooplankton species in the Great Lakes; average numbers from a 1970 sample of Otsego Lake showed densities of 30,000 organisms per m³.
Comments: Probable ballast water introduction.

  Schodler, 1877 (spiny waterflea)

Habitat: Large and small temperate lakes, can tolerate brackish water.
Life History: Can reach 15 mm; can reproduce asexually; unfertilized eggs carried in a brood pouch; fertilized eggs layed in the fall and hatch the following spring.
Native Range: Northern Europe and Asia.
Nonindigenous Range: Lake Erie and Lake Ontario.
Impacts: Compete directly with larval fish for food; fouls fishing gear.
Comments: The tail spine can comprise over 70 percent of the animal’s length and has one to three pairs of barbs; first detected in 1984 in Lake Huron, probable ballast water introduction.

  Ostroumov, 1891 (fishhook waterflea)

Habitat: Brackish and freshwater lakes.
Life History: Body size from 1-3 mm in length without tail, 6-13 mm with tail; tail has three pairs of barbs and a characteristic loop near the end; can reproduce asexually during the summer; sexual reproduction occurs in the fall when water temperatures decline; exhibit diurnal vertical migrations in native range; predatory feeding habits on other zooplankton.
Native Range: Caspian, Azov, and Aral seas of Europe and Asia.
Nonindigenous Range: Lake Erie (Presque Isle in 2002), Lake Ontario in 1998, Fingers Lakes of New York (Canandaiga, Cayuga, Keuka, Cross, Otisco, Owasco, Seneca).
Impacts: Fouls fishing gear; potential for competition with other planktivores for food.
Comments: C. pengoi has been found in the stomach of some fishes in high percentages in Europe.