(Stebbing, 1899) (an amphipod)

Habitat: Shallow margins of lakes and large rivers with gravel or rocky bottom; can tolerate lakes with mud bottoms.
Life History: Body length can reach 8 mm; females brood sizes can have as many as 48 individuals in their native range and can reproduce all year in favorable conditions.
Native Range: Ponto-Caspian region of Eurasia.
Nonindigenous Range: Lake Erie and Lake Ontario.
Impacts: Maybe replacing the native Gammarus fasciatus in the Great Lakes.
Comments: Has become the dominant amphipod in many locations; very often associated with Dreissena colonies.

  Bousfield, 1969 (an amphipod)

Habitat: Oligohaline estuarine species, found to be primarily pelagic but also epibenthic in estuaries, bays and sounds, also tolerates freshwater habitats.
Life History: Size 8-12 mm; sexual maturity reached in about 30 days; clutch size of female increases with size of individual; highest reproduction potential occurs in spring and summer months with short time required for maturation and incubation and continuous reproduction; reproductive activity remains constant until G. daiberi enters into overwintering cycle.
Native Range: Northwestern Atlantic coast from Delaware to South Carolina.
Nonindigenous Range: Earliest record from NY is 1975 in the Hudson River estuary from the Battery to Albany and later found at Indian Point as well as in the Hudson River freshwater tidal reach.
Impacts: Unknown.
Comments: Dense populations have been found in the Hudson estuary; most likely a ballast water introduction.