On the distribution of <i>Eurytemora affinis</i>(Poppe) (Copepoda) in the Western Scheldt estuary

In the Scheldt estuary, E. affinis appeared place-bound, dependent on a direct import from quiet breeding-places in connection with the main stream as in the case of mud-flat-saltmarch systems and on an indirect import as in the case of harbours and sluice-docks. This import explains the place-bound presence in different geographically separated places along the axis of the estuary and its presence at different chlorinities, varying between sea and freshwater (17.9-0.071 promille Cl-). The stream itself did not appear to have its "own" autochthonous population. The facts tend to prove that besides physical characteristics of the system, such as the estuarine circulation and the salinity-distribution, the hydro-geographical detail structure of an estuary can be of major importance and can contribute to the maintenance and presence of a species