Bruinvisonderzoek

Since 1980, the number of stranded harbour porpoises along the Dutch coast has initially increased sharply and subsequently stabilised at a high level. Sections of harbour porpoises washed ashore have shown that both anthropogenic induced causes of death as well as natural causes are responsible. Diet research on stranded harbour porpoises has shown that a relatively large amount of fish with a low fat content is eaten in the Netherlands. How this lean diet affects the health and reproductive capacity of harbour porpoises in Dutch waters is still subject of study.

In this project, the contents of the stomachs of stranded harbour porpoises are analyzed to monitor their diet. The diet is an factor for the presence, condition and reproductive capacity of harbour porpoises in Dutch waters and ultimately for their population development. A good ecological status therefore requires sufficient availability of suitable prey. We hereby take into account the fact that research on stranded harbour porpoises mainly shows the diet of animals that had their last meal close to the coast. By distinguishing between animals that died quickly and in good condition (seal and net victims) versus animals that died slowly, due to disease or infirmity, it is possible to determine what the diet of the 'healthy part of the population' in the coastal zone is. To determine how the diet close to the coast compares to the diet of animals that forage further offshore, animals that perish further offshore should be studied. In the Netherlands it has so far proved difficult to obtain animals from offshore of the North Sea. It will therefore (also) be investigated whether the inshore/offshore comparison can be made through collaboration with researchers in Germany and Denmark in order to obtain sufficiently large numbers of 'offshore' harbour porpoises. The possibilities of using other techniques for dietary research, such as research using stable isotopes or prey DNA, will also be further explored .