A Multivariate Model for Predicting Population Fluctuations of Dreissena polymorpha in North American Lakes

The European zebra mussel, Dreissena polymorpha (Pallas), has recently been introduced to North American freshwaters. Dreissena exhibits a wide range of population dynamics among different European lakes. In some lakes, long-term population size is fairly constant, while populations in other lakes can fluctuate greatly from year to year. Assessments of the potential ecological and economic effects of Dreissena in North America will be affected if populations show large interannual fluctuations in abundance. We develop a multivariate model for predicting population dynamics of Dreissena in novel lake systems. Our model uses the limnological differ-ences between lakes with constant populations of Dreissena and those with variable populations to identify variables that may determine population dynamics. We find that lakes with more constant populations tend to have larger surface areas, lower levels of calcium, and higher levels of phosphate (PO,) compared with lakes with more variable populations. La dreissénie européenne, Dreissena polymorpha (Pallas), a récemment été introduite dans les eaux deuces de I’Amérique du Nord. Les Dreissena des lacs européens présentent une large gamme de dynamiques de popu-lation. Dans certains lacs, la taille de la population est passablement constante à long terme tandis que les populations d’autres lacs fluctuent grandement d’une année à I’autre. Les évaluations des effets écologiques et économiques éventuels des Dreissena en Amérique du Nord donneront des résultats variables si les population