Long-term demography of a zebra mussel (Dreissena polymorpha) population

1. We used long-term data and a simulation model to investigate temporal fluctuations in zebra mussel populations, which govern the ecological and economic impacts of this pest species. 2. The size of the zebra mussel (Dreissena polymorpha) population in the Hudson River estuary fluctuated approximately 11-fold across a 13-year period, following a cycle with a 2-4 year period. 3. This cycling was caused by low recruitment during years of high adult population size, rapid somatic growth of settled animals, and adult survivorship of 50% per year. 4. Adult growth and body condition were weakly correlated with phytoplankton biomass. 5. The habitat distribution of the Hudson's population changed over the 13-year period, with an increasing proportion of the population spreading onto soft sediments over time. The character of soft-sediment habitats in the Hudson changed because of large amounts (mean = 34 g DM m(-2)) of empty zebra mussel shells now in the sediments. 6. Simulation models show that zebra mussel populations can show a range of long-term trajectories, depending on the balance between adult space limitation, larval food limitation, and disturbance. 7. Effective understanding and management of the effects of zebra mussels and other alien species depend on understanding of their long-term demography, which may vary across ecosystems.