Eiders, Mussels, and Fisheries in the Wadden Sea - Continuous Conflicts or Relaxed Relations?

• Main Authors: Nehls, Georg, Ruth, Maarten
• Format: Article in Journal/Newspaper
• Language: English
• Published: University of Copenhagen, Marine Biological Laboratory 1994
• Subjects: Somateria mollissima
• Online Access: https://oceanrep.geomar.de/id/eprint/42886/; https://oceanrep.geomar.de/id/eprint/42886/1/Ophelia%20Suppl.%206%20pp%20263-278%20%281994%29.pdf

Eider, Somateria mollissima, and mussel, Mytilus edulis, stocks were studied in the Wadden Sea of Schleswig-Holstein with respect to interactions with mussel fisheries. Mussel fisheries take place by means of 2,800 ha of bottom cultures, with seed mussels taken from natural beds. Fisheries have a marked influence on total mussel stocks. The amount of mussels found on the culture lots and annual landings of up to 40,000 tons may exceed natural stocks. About 130,000 eiders use the Wadden Sea of Schleswig-Holstein for moulting and on average about 70,000 stay over the winter. Mussel cultures are estimated to provide on average about 10 to 20% of the food of eiders. However, the number of wintering eiders utilizing the cultures varies in relation to the amount and size of the mussels present and ranges from 10 to 60%. No evidence was found that eiders have a measurable impact on the yield of the cultures and no response of eider numbers to increasing culturing could be detected. Mussel fisheries are regarded as a potential threat to eiders, because they might reduce total mussel stocks considernbly and might affect eider numbers in years of low bivalve stocks. It is recommended to regulate the fisheries in order to prevent overfishing of mussel stocks, which recently happened in other parts of the Wadden Sea.