Last year, many new mussel banks were observed in the Wadden Sea for the first time since 2005. Researchers at the Mosselwad project – in which IMARES Wageningen UR is a partner – have reported the appearance of many new seed beds with young mussels, especially in the eastern Wadden Sea.
The Dutch government wants to see more old and stable mussel beds in the Wadden Sea because they make an important contribution to the valuable ecological processes for which the Wadden Sea is famous. The aim of the Mosselwad project is to assist the recovery of mussel banks in the Wadden Sea by monitoring the development of self-replenishing mussel beds (existing and experimental) and by utilising the findings to establish new experimental mussel beds.
Every spring and autumn since 1995 IMARES has compiled an inventory of the number of mussel beds: have new banks appeared or have previously observed banks disappeared? The surface area and thickness of the mussel beds are measured and the development of the mussels is followed: mussel sizes are recorded and the numbers counted. New growth and demise are mapped out. The research seeks to explain why mussel beds are located at some places rather than others and to ascertain the factors that lead to their disappearance. Experiments have been conducted in which mussels are added to existing shell beds (oysters, mussels) and the development of the beds is then studied. The findings enable IMARES to provide advice on the establishment and recovery of mussel beds in the Wadden Sea.
The oldest musselbeds date from 1994. Between 1989 and 1991 all had disappeared because of fishery. Since 1994 the numbers increased and, in 2001, 4,000 hectares of young mussel banks emerged at once. Many disappeared again in the winters that followed. In 2005 there was again a reasonable spatfall of approximately 1,000 hectares, followed only by a gradual decline. Fortunately, many new young mussel banks appeared again in 2012. In April 2013 IMARES researchers will be exploring how they managed to survive the winter.
Mosselwad, which is co-funded by the Wadden Sea Fund, the Directorate-General for Public Works and Water Management (Rijkswaterstaat) at the Ministry of Infrastructure and the Environment, and the provinces of North Holland and Friesland, will run until 2015.
Mosselwad: an association of Kust & Zee with IMARES Wageningen UR, the Royal Netherlands Institute for Sea Research (NIOZ), SOVON Vogelonderzoek Nederland (ornithological research) and the Faculty of Geosciences at Utrecht University.
Photo: Bruno Ens