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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Lentic Ecology
ECHINOGAMMARUS ISCHNUS, THE NEXT EXOTIC THREAT?
C.M. Mayer1, J. Philippon1, S.A. Heckathorn1, N. Tisch2, and J. Haynes3. 1Biology Department, Syracuse University, Syracuse, NY 13224, 2Department of Biometrics, Cornell University, Ithaca, NY 14850, 3Department of Biological Sciences, SUNY Brockport, Brockport, NY 14420
The European amphipod, Echinogammarus ischnus, is one of many exotic species recently introduced to the Laurentian Great Lakes. We studied the potential of E. ischnus to impact the resident amphipod, Gammarus fasciatus, currently an important food-web component in near-shore areas. In habitat choice experiments G. fasciatus preferred Dreissena-covered rocks to algae-covered rocks, bare rocks, and artificial plants; E. ischnus showed no significant preference. In the laboratory, rock bass (Ambloplites rupestris) showed a slight preference for G. fasciatus. G. fasciatus showed a trend towards greater activity levels, possibly making them more vulnerable to fish predation. G. fasciatus grew faster, matured earlier, and had a higher metabolic rate than E. ischnus at several temperatures. At one site in Lake Ontario the density of G. fasciatus was related to Dreissena cover, but not algal cover or depth; whereas E. ischnus density was related to Dreissena cover, algal cover, and depth. At two sites in Lake Ontario abundance of E. ischnus increased relative to G. fasciatus only during the late fall. Therefore, the resident species G. fasciatus remains the numerically dominant amphipod throughout most of the season in near-shore Lake Ontario.
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