Bruinvis Phocoena phocoena in het Grevelingenmeer: een bijzonder geval met afwijkend gedrag

Harbour Porpoises in Dutch coastal waters have dramatically increased in abundance since the mid 1980s and early 1990s. In the Zeeland Delta area, however, an increase in sightings occurred not before 2001. Another difference between coastal sightings north of Hook of Holland and sightings in the Delta area is the seasonal pattern: primarily winter/spring visitors in the north, year-round in Zeeland. One particular case in Zeeland is described in detail, incidentally representing the first case of a Harbour Porpoise that could be individually recognized from developing scratches on the skin and notches in the dorsal fin. This animal, found in the salt water lake Grevelingenmeer in August 2006, is a fanatic bowriding porpoise, following sailing and motoring yachts and even surfboards for prolonged periods of time. From this case, we know for sure that individual porpoises can stay for over a year in the same general area, as resident dolphins. The behaviour of this particular animal is unprecedented, at least within The Netherlands.