Consumption of Zebra Mussels Dreissena polymorpha by diving ducks in Lakes Erie and St. Clair

Abstract

Zebra Mussels are a novel and abundant prey item for diving ducks in the Laurentian Great Lakes region. We investigated use of Zebra Mussels as food by several species of diving ducks (Greater and Lesser Scaup, Common Goldeneye, Bufflehead, White-winged Scoter and Old-squaw) in Lakes Erie and St. Clair in 1990 and 1991. We examined 135 gizzards from ducks shot by hunters (fall) and ducks drowned in fishing nets (spring). We noted presence or absence of Zebra Mussels, and estimated lengths of mussels consumed. Mussels were eaten by all species examined and were consumed by ducks at each location. Overall, 52% of gizzards contained Zebra Mussels, including all those from Point Pelee, Ontario. Larger duck species tended to consume larger mussels, but prey sizes taken varied widely among locations. Although diving ducks probably were size-selective predators, they ate mussels from a wide size range. This suggests that at most locations where Zebra Mussels occur, some mussels of an acceptable size will always be present for ducks.