The Hard Bottom Biocoenoses and the Fish Fauna of Lake Grevelingen, and Their Reactions to Changes in the Aquatic Environment

In 1970 the Biological Working Group of the Dutch Underwatersports Association started an investigation of the hardbottom biocoenoses in the Grevelingen. Since 1979 we extended the investigation and since 1980 a monitoring investigation of the fish fauna in Lake Grevelingen has also been carried out. The aims of the investigations are to gain insight into the presence and coverage of the hard bottom biocoenoses and their reactions to changes in the aquatic environment, as well as to gain a continuous up-to-date insight into the presence of the various fish species, so that (management) measures can be advised. In this paper, the results obtained in the period 1970 to 1983 are given. The authors recommend opening the sluice in the Brouwersdam for much longer periods and carrying out an active management using this sluice and the siphon sluice in the Grevelingendam, which can be put into use at the end of 1983.