De Dreissena-gemeenschap in Nederland, tien jaar na de eerste waarneming van de Quaggamossel in Nederland

This contribution starts with the distinction between Quagga mussels, Dreissena rostriformis bugensis, and Zebra mussels, Dreissena polymorpha, based on external characteristics (figures 1-5). An overview is given of the Quagga mussel spread in The Netherlands, ten years after its first observation in Western Europe on April 19, 2006. At present they already colonized all main freshwater bodies constituting a network of waterways. Introduction in smaller local water bodies mainly depends on connectivity with the national network of waterways from point of view of navigation (commercially and recreationally) and water quantity management. In three lakes, IJsselmeer, Markermeer and Volkerak, in which the dreissenids has been monitored, the Quagga mussel had a positive effect on the dreissenid density. Moreover, due to differences in traits, within two or three years the Quagga mussel dominated the dreissenid community in those lakes. Future developments in the dreissenids community are hard to predict. Introductions of other invasive exotic species can play an important role. The Golden mussel, Limnoperna fortunei, is indicated as a potential newcomer, being a food and place competitor for the dreissenids.