COLONIZATION, ECOLOGY, AND POPULATION-STRUCTURE OF THE QUAGGA MUSSEL (BIVALVIA, DREISSENIDAE) IN THE LOWER GREAT-LAKES

An invasive dreissenid mussel given the working name of ''quagga'' has a present (spring 1993) distribution in the Laurentian Great Lakes from the western basin of Lake Erie to Quebec City. In Lake Erie, quaggas were collected as early as 1989 and now are most common in the eastern basin. In Lakes Erie and Ontario, proportions of quaggas increased with depth and decreasing water temperature. ln the eastern basin of Lake Erie, quaggas outnumbered zebra mussel (Dreissena polymorpha) by 14 to 1 in deeper waters (>20 m). In Lake Ontario, quaggas were observed at depths as great as 130 m, and both quagga and zebra mussel were found to survive at depths (>50 m) where temperatures rarely exceed 5-degrees-C. Quaggas were sparse or absent along inland waterways and lakes of New York State. Mean shell size ot quagga mussel was larger than that of zebra mussel at sites in the Niagara River, Lake Ontario, and the St. Lawrence River. The largest quaggas (38 mm) were observed in the St. Lawrence River at Cape Vincent.