Demography and growth of the exotic zebra mussel (Dreissena polymorpha) in the Rideau River (Ontario)
Although many biological studies of the zebra mussel, Dreissena polymorpha, have been conducted in lake systems of Europe and, more recently, North America, there is little information about the life-history characteristics of this mollusc in river systems. In the present study, the demography and growth of D. polymorpha were studied in the Rideau River (over a distance of ca. 100 km), Ontario, in 1990, 1993, and 1994. This period coincided with the time of its discovery (October 1990) and rapid population increase (1994) in the river. During 1990, zebra mussels were discovered on the hull of a large steel boat but were not observed on any other substrate. During 1993, zebra mussels were common (1–24 mussels/m2) on reefs, locks, wharves, buoys, and boat hulls in the northern, downstream section of the river near Ottawa, Ontario. During 1994, densities of mussels increased 100- to 10 000-fold (156–23 000/m2) in the downstream section, but remained rare in the upstream section (0–1/m2). Size distributions of young of the year in 1993 and 1994 indicate that mean growth rates of D. polymorpha in the Rideau River (0.090–0.139 mm∙d−1) are comparable to those reported for the Great Lakes and European rivers.