Walvissen, dolfijnen en bruinvissen voor de Engelse oostkust, september 1989

On board the fishery research vessel MV Tridens seabirds and marine mammals were counted during three weeks in September 1989 off the English east coast (53-56’N). The total number cetaceans seen was 341: 6 species in 71 herds. A review is given of the distribution of the sightings (maps 1-3) with some remarks on the behaviour of the animals. In the waters visited, very high densities of auks were found and the area was clearly rich in small fish (mainly clupeids) offering excellent feeding conditions. Interesting sightings were 4 Minke Whales, 19 Pilot Whales and 50 Common Dolphins. White-beaked Dolphin and Harbour Porpoise (141 and 80 respectively) were common. White-sided Dolphins were positively identified on 5 occasions (18 individuals), 29 dolphins remained unidentified. Mean herd sizes were 1.9 ± 1.4 in Pilot Whales (n= 10 herds), 7.05 ± 7.5 in White-beaked Dolphins (n= 20 herds; 3 herds >10: 14, 15 and 35 individuals), and 3.8 ± 3.0 in the Harbour Porpoise (n= 21 herds; maximum 10 individuals). The Common Dolphins were fishing (with a group of Gannets associated), and their methods are briefly described. Sightings of White-beaked and White-sided Dolphins were highly concentrated between 64°30 and 55°30 N, just to the west of Greenwich. Harbour Porpoises had a more southerly and distinctly more easterly distribution. Sightings of Minke Whales and Pilot Whales were scattered in a broad band along the coast. It is suggested that ecological differences are responsible for the different distribution patterns but an explanation is hard to give.