De mollusken van Rottumerplaat 2006. Verslag van een inventarisatie in het kader van het Project Habslak en het Atlasproject Nederlandse Mollusken

In September 2006, the authors, Menno Soes and David Baron made an inventory of the malacofauna of the Waddenzee island Rottumerplaat, the results of which are reported here. Due to the restricted access to the island, the malacofauna was so far not very well known. On the terrestrial part of the island, including the salt marshes, 18 species were found alive, which brings the total number of known species to 22 (see table 1). The most remarkable species is Vertigo angustior, which is included in Annex II of the EU Habitat Directive. Although this species is more frequently found in the dunes along the west coast of the Netherlands, this is only the second observation of this species in the Wadden Sea region, the first one being in 1936. Other red list species are Assiminea grayana, Ovatella myosotis, and Vertigo pygmaea. Freshwater molluscs do not live on Rottumerplaat. The marine mollusc fauna in the direct surroundings of the island is very rich. 15 species of marine molluscs were found alive, a.o. vital populations of Abra tenuis and Retusa obtusa (table 2). Our results reflect the high natural value of Rottumerplaat. Compared to other Dutch wadden islands, Rottumerplaat is more dynamic; in addition, it is strictly protected against disturbance by fishermen and tourism. Although the causal relationship is not proved, these circumstances seem to be profitable for the development of a rich mollusc fauna.