Cercopagis is a Ponto-Caspian native whose first presence in North America occurred in Lake Ontario, 1998. The species has since spread to Lakes Michigan and 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 below, Laxon et al. 2003, Freshwater Biology). It has also 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. If this occurs in Lake Erie, the commercial fishing industry could be affected (see below). We expect Cercopagis to continue to spread, much like its relative Bytotrephes.
From Laxon et al. (2003, Freshwater Biology):
-Cercopagis pengoi (Ostroumov) was first detected in Lake Ontario. The initial impact on the lower food web of Lake Ontario was explored through assessments of historical and seasonal abundance of the crustacean zooplankton community
-Decreases in the abundance of dominant members of the Lake Ontario zooplankton community between 1999 and 2001 [i.e. Daphnia retrocurva Forbes, Bosmina longirostris (OF Muller) 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 food limitation was not responsible. Chlorophyll-a concentration generally increased concomitant with declines in herbivorous cladoceran zooplankton abundance in the lake.
-Laboratory experiments demonstrated that Cercopagis fed on small-bodied species including D. retrocurva and B. longirostris
-Consumption demand of mid-summer populations of Cercopagis, estimated from the bioenergetic model of cofamilial Bythotrephes, was sufficient to decimate the crustacean community at certain times, although the degree of expected suppression varied seasonally and interannually
-Predatory effects exerted by Cercopagis on the Lake Ontario zooplankton community, while initially very pronounced, have decreased steaily since the species became established. When abundant (1999), Cercopagis predation on herbivorous zooplankton cascaded through the lower food web with increased phytoplankton abundance
Changes in Zooplankton Community:
Fouling of Gill Nets: