Cercopagis pengoi Ostroumov, 1891

Via competition for food C. pengoi has the potential to affect the abundance and condition of zooplanktivorous fish, fish larvae and mysids. In its invasive range the species become important food for the alewife, nine-spined stickleback, bleak, herring and smelt (Uitto et al., 1999; Benoit et al., 2002; Vanderploeg et al., 2002; Bushnoe et al., 2003; Kotta et al., 2004, 2006; Põllumäe and Kotta, 2007). (CABI, 05/06/2021)

The predatory impacts of Cercopagis pengoi, a planktivorous cladoceran first observed in Lake Ontario in 1998,were assessed by examining patterns in the distribution and population dynamics of macrozooplankton. Specifically,we determined the vertical distribution of C. pengoi in Lake Ontario with respect to other zooplankton species andpossible biotic and abiotic controlling factors and used seasonal time series of potential prey species, both beforeand after C. pengoi invasion, to make inferences about predatory impacts of C. pengoi. The highest abundances ofC. pengoi generally occurred at the bottom of the epilimnion or at the top of the metalimnion, and strong dielvertical migration was not observed. The vertical distribution of cyclopoid and calanoid nauplii and copepodidswas deeper in 1999 than had historically been observed, which suggest possible avoidance of C. pengoi or localizedpredatory depletion. Seasonal analyses of normalized biomass size spectra from the Bay of Quinte supported animpact of C. pengoi on organisms,0.1mg dry weight. The hypothesized predatory effect on juvenile copepodswas supported by an analysis of seasonal time series, where we observed that high abundances of C. pengoicoincided with marked decreases in these groups. Consequently, the presence of C. pengoi likely decreases theproduction of juvenile copepods both through direct predation and through a shift of copepod vertical distributionto colder waters. Among the cladocerans, only Bosmina longirostris abundance declined in the presence of C.pengoi in the analysis of seasonal time series. Benoît et al., 2002).

Long-term observations on the dynamics of the Vistula Lagoon zooplankton community revealed that the appearance in the ecosystem of a new large crustacean capable of predatory feeding caused changes in the structure and functioning of zooplankton. Under the influence of C. pengoi, a transformation of the structure of the zooplankton community occured owing to the complexity of the food web, which began to be closed by two plankton predators. At the same time, despite the decrease in the values of the Impact Index, which reflects the trophic pressure of the invader on zooplankton, there was observed a significant decrease in the abundances and production of the dominant species, especially Eurytemora affinis. A similar trend of changes in plankton under the influence of C. pengoi is also a characteristic of other estuaries of the Baltic Sea. (Naumenko & Telesh, 2019)