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 w...