Cetaceans and pinnipeds, June – August 1991

German Bight surveys in June did not result in any cetaceans. However, 4 White-beaked Dolphins Lagenorhynchus albirostris, 6 unidentified dolphins and 23 Harbour Porpoises Phocoena phocoena were encountered north of 56°N this month (CJC). Harbour Porpoises seen on 10 and 11 June in the central North Sea (respectively at 57°15.1’N, 3°50.1’E and 57°14.6’N, 2°20.3’E), were adults and very small (newborn) calves. There were no sightings during the aerial survey in July, although weather conditions were very good most of the time. In previous years, July has always been poor for ”plane based” cetacean sightings, which is remarkable since June usually is the best month on the Dutch Continental Shelf (DCS). On the other hand, surveys on board MV Tridens II in July in the central North Sea and off NE Scotland led to a large number of sightings (HO, TG): 2 unidentified whales, 16 unidentified dolphins 10 Minke Whales Balaenoptera acutorostrata, 7 White-beaked/While-sided Dolphins, 10 White-sided Dolphins Lagenorhynchus acutus, 159 White-beaked Dolphins, and 39 Harbour Porpoises. Most cetaceans were encountered off NE Scotland (Aberdeen Bank/Long Forties; see map). One Minke Whale in the southern North Sea was seen breaching. Several of the White-beaked Dolphins were seen at the bow of the ship. Herd size in Whitebeaked Dolphins and Harbour Porpoises averaged 5.3 ± 3.5 (range 2-15, n= 30), and 2.3 ± 1.2 (range 1-5, n= 17) respectively.