DISTRIBUTION AND ABUNDANCE OF SHALLOW-WATER HYPERBENTHIC MYSIDS (CRUSTACEA, MYSIDACEA) AND EUPHAUSIIDS (CRUSTACEA, EUPHAUSIACEA) IN THE VOORDELTA AND THE WESTERSCHELDE, SOUTHWEST NETHERLANDS

The hyperbenthic mysids and euphausiids of the subtidal shallow coasta l waters (the Voordelta) and the Westerschelde estuary in the Delta ar ea (SW Netherlands) were regularly sampled between 1988 and 1991. Two salt marshes in the brackish part of the estuary were studied in the s ame period. Eight mysid species and one euphausiid species were identi fied. The spatial and seasonal distribution patterns of all species ar e described. The most abundant species in the coastal area is Schistom ysis spiritus, followed by Mesopodopsis slabberi, Schistomysis kervill ei, and Gastrosaccus spinifer. In the marine part of the Westerschelde the same four species are dominant but densities are generally higher than in the coastal area. Only Siriella armata and the euphausiid Nyc tiphanes couchi never enter the estuary. Highest mysid densities, main ly M. slabberi and the estuarine endemic Neomysis integer, are found i n the brackish part of the Westerschelde. Praunus flexuosus is a euryh aline species with a preference for the intertidal areas. The estuarin e populations of N. integer, M. slabberi, P. flexuosus, and - to a les ser extent - S. spiritus seem to utilise the salt marshes during perio ds of reproduction.