Tidal influences on the distribution of the harbour porpoise Phocoena phocoena in the Marsdiep area, the Netherlands
Tidal influences on the distribution of the harbour porpoise Phocoena phocoena in the Marsdiep area, the Netherlands
Samenvatting
Harbour porpoises (Phocoena phocoena) are the smallest cetaceans in the North Sea. They have recovered from being rare to nowadays being present throughout the year in numbers reaching to 80 000 in the Dutch sector or the North Sea. The only area where studies were conducted prior to the disappearance of the harbour porpoise from Dutch waters was in the Marsdiep by Verwey between 1931-1973. The Marsdiep area is a tidal inlet between the mainland of Noord-Holland and the Wadden Sea island Texel. The historical research by Verwey was conducted along the shores of the Marsdiep between Huisduinen and the harbour of Den Helder. He noted harbour porpoises visiting the harbour entrance at high tide and movements influenced by ebb and flood tides were documented. Verwey questioned if ”Phocoena has special reactions on the tides?”. With the harbour porpoise nowadays being present in high numbers in the early spring months, this resulted in the hypothesis of this research: harbour porpoises move into the Marsdiep area with upcoming tides and out during ebb. The main question raised is: ‘Is there an association between the presence of harbour porpoises and the tidal cycle in the Marsdiep area?’.
Organisatie | Van Hall Larenstein |
Afdeling | Kust en Zee Management |
Partner | Hogeschool Van Hall Larenstein |
Wageningen Institute for Marine Resources and Ecosystem Studies | |
Nederlands Instituut voor Onderzoek op Zee | |
Datum | 2013-05-29 |
Type | Bachelor |
Taal | Engels |