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Cercopagis is a Ponto-Caspian native that was first recorded in North America in Lake Ontario in 1998. The species has since spread to Lake Michigan, Lake Erie and to inland lakes in the Finger Lake area of New York State. The species has caused very significant changes to the plankton community of Lake Ontario (see Laxon et al. 2003, Freshwater Biology)(below). It also has caused severe fouling of fishing nets in Lake Erie during summer 2002. Russian fishermen (Black Sea) whose gill nets are fouled by this species when it is abundant will not put their nets in the Black Sea because the fouling problem is too severe (they call it 'frost'). If this occurs in Lake Erie, the commercial fishery could be affected. (see below). We expect Cercopagis will continue to spread, much like its relative Bytotrephes.
From Laxon et al. (2003, Freshwater Biology paper).
Summary
1. Cercopagis pengoi (Ostroumov) was first detected
in Lake Ontario. We explored the impact of Cercopagis on the
lower food web of Lake Ontario through assessments of historical and seasonal
abundance of the crustacean zooplankton community, by conducting feeding
experiments on the dominant prey, and by estimating consumption requirements
of Cercopagis.
2. Between 1999 and 2001, decreases in the abundance of dominant members of the Lake Ontario zooplankton community (Daphnia retrocurva Forbes, Bosmina longirostris (OF Müller) and Diacyclops thomasi (Forbes)) coincided with an increase in the abundance of Cercopagis. Daphnia retrocurva populations declined despite high birth rates in all three years, indicating that food limitation was not responsible. Chlorophyll-a concentration generally increased concomitant with declines in herbivorous cladoceran zooplankton abundance in the lake.
3. Laboratory experiments demonstrated that Cercopagis fed on small-bodied species including D. retrocurva and B. longirostris.
4. Consumption demand of mid-summer populations of Cercopagis, estimated from the bioenergetic model of confamilial Bythotrephes, was sufficient to decimate the crustacean community at certain times, although the degree of expected suppression varied seasonally and interannually.
5. Predatory effects exerted by Cercopagis on the Lake Ontario zooplankton community, while initially very pronounced, have decreased steadily since the species was established in the lake. When it was abundant (1999), Cercopagis predation on herbivorous zooplankton cascaded through the lower food web with increased phytoplankton abundance.
Changes in zooplankton community of Lake Ontario after
predatory Cercopagis invaded. Three
previously-dominant taxa have declined significantly
in abundance after the invasion.
Cercopagis fouling of gill nets in Lake Erie. Russian fishermen call it 'frost'.
