Abstract
We want to develop and test a simple conceptual model of invasions of marine exotic species. This model considers only one donor region, one vector, and one recipient region. It assumes that the rate of inytoductions in the latter region is dependent on: 1.the supply of species by the donor region; 2..the nature and the magnitude of the vector responsible for the transport; 3.the nature of the recipient region, in particular the number of species already established in that region. This model predicts that the introduction rate will be high shortly after the connection between the two regions has been established and that this will decrease gradually. This prediction, which seems to contradict available data, will be tested by means of three data sets derived mainly from literature, viz. a.the introduction of fouling species on ship's hulls from the Atlantic coast of North America to the Atlantic coast of Europe; b.the introduction of Ponto-Caspian species into NW Europe via intra-continental freshwater canals; c.the introduction in NW-Europe of Japanese species through the introduction of Japanese oysters. The second data set will be enlarged to estimate numbers of species still to be expected in NW-Europe by sampling along the Danube. The introduction rate of Japanese species will be estimated by monthly field samples of Japanese oysters to determine the possible similarity between independent introduction events.
Netherlands