The calanoid copepod Eurytemora velox (Lilljeborg, 1853) first appeare
d in the plankton in the floodplain waters and main channel of the Slo
vakian-Hungarian stretch of the Danube in 1998. In the two years since
its first siting, it has spread to further localities in this area. T
he author considers passive transport of resting eggs by birds to be t
he most probable mode of immigration of the species into the Middle Da
nube (from the lowest section of the Danube lower course). He predicts
the distribution of E. velox will eventually extend into other sectio
ns of the middle and lower reaches of the Danube and does not exclude
its finding also in the Austrian stretch of the river.