Marine mammals, March – May 1992

The only cetacean seen during offshore surveys in this period was the Harbour Porpoise Phocoena phocoena. During the extensive surveys in (shallow) coastal waters of the German Bight in April, some 82 porpoises were spotted (see map). With 56 sightings, the average herd size was 1.46 ± 0.73 (range 1-4 individuals). Most animals were seen just off BlSvandshuk, Denmark, in a very shallow area known as Horns Rev (MFL). Most of the rest was observed just off the German Wadden Sea islands (Sylt-Silderoog; MFL, HS). The 23rd of April was the most spectacular day, with no less than 36 sightings (flat calm conditions). As usual, little notes on behaviour could be made, for a ship like MV Navicula will scare porpoises away. However, three sleeping individuals were spotted and some porpoises remained quiet and were seen surfacing several times. There were no indications for the presence of calves. Not a single porpoise was seen during cruises off the Dutch Wadden Sea islands. The last Harbour Porpoise of this winter, as seen during seawatches in Noord-Holland, was recorded at Egmond aan Zee on 15 March (SL). In all, this leaves us with 14 sightings (18 individuals) during seawatches between October 1991 and May 1992 (last sighting in March). One was seen at Schiermonnikoog (12 Oct), 1 at Den Helder (19 Oct), the rest at either Camperduin or Egmond in Noord-Holland (NH). Seawatching data leave us this season with an average herd size of 1.28 ± 0.8 individuals. A paper on the occurrence of the Harbour Porpoise in the southern North Sea is now in preparation (Camphuysen, Leopold & van der Ham).