This report summarises our existing knowledge on the distribution and numbers of seaduck, particularly the Common Scoter Melanitta nigra in The Netherlands, in relation to its primary food species, the Common Trough Shell Spisula subtruncata. This is done to aid the further development of a policy to deal with the developing fishery for this bivalve. Obviously, fishermen and birds may compete for the same resource, rich banks of Spisula, and this may result in a conflict between economical and conservation objectives. Research on both seaduck and Spisula has been carried out by the author and co-workers since 1988, and an overview is presented here.Common Scoters have been found by at least the tens of thousands in our coastal waters since the late 19th century. In the 1990's, flocks of our 100.000 birds were present over the Spisula-banks, and the birds have been shown to take this species in any yearclass. Spisula subtruncata is potentially a very common species in the coastal zone, but may show very large numerical fluctuations. From the ducks' point of view, fisheries and birds do not mix very well. The mere activity of fishing causes considerable disturbance, and it may decimate the only food source available to the ducks. On the other hand, the ducks do not seem to use all available Spisula-banks, so there is room for both fishermen and ducks, providing that more banks are available.Two avenues for future policy seem possible to develop a sustainable fishery, while at the same time conserve the ducks in our country. The size of the whole Spisula resource may be assessed yearly, after wich a quotum may be given to the fishing industry, in the fashion of the shellfish policy currently used in the Wadden Sea. Alternatively, the fishery could be closed in the area that the ducks use, whilst it is opened in all other areas. The latter policy requires a yearly assessment of numbers and whereabouts of the birds, but this may also be used for other purposes, such as monitoring and increasing the effectiveness of combatting oil pollution.
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