On Sunday the 22nd of January 2017 there was a special observation at sea: a very rare marine mammal, a dwarf sperm whale (Kogia sima) has been spotted near Ostend!
That Sunday the association North Sea Pelagics vzw organised a trip at sea in the Belgian part of the North Sea for observing marine mammals and seabirds. The weather conditions were perfect: sunny and no wind, and many porpoises, our most common cetacean, were observed (about 90). At about 14:30h a cetacean was observed near the Kwintebank. There was immediate doubt as to whether this was a harbour porpoise. The animal seemed bigger than the porpoises observed before, and the shape of the animal and behaviour were different. After the trip, the photos were thoroughly examined by Belgian and foreign specialists.
The conclusions of the specialists were clear: all features, including the relative size of the dorsal fin and the distance from the dorsal fin to the head, indicate that this is not a porpoise, but a dwarf sperm whale (Kogia sima). The dwarf sperm whale can attain a length of 2.7 m, that is larger than a harbour porpoise which is usually 1.8 m. At sea they it can be mistaken for a porpoise. The January 22 observation was the first in Belgian waters. The dwarf sperm whale is normally more restricted to the tropics, with very few records in Europe: France (1986, 1991, & 1999), Spain (1987), and Italy (1988 & 2002), and a first stranding in the United Kingdom in 2011. In that case, the still living animal could be put back into the sea, and the identification could be done retrospectively on the basis of photographs.
Records of pygmy sperm whales, a closely related species of which the range extends into the subtropics, have been increasing in recent years in UK waters. Both species of Kogia are difficult to tell apart at sea, but the Pygmy Sperm Whale has a much smaller and back-curved dorsal fin.
A special thanks goes out to Jeremy Demey (North Sea Pelagics vzw), Jan Haelters (Royal Belgian Institute of Natural Sciences - RBINS), Gorka Ocio (Verballenas), Peter Evans (Sea Watch Foundation), Robin Baird (Kogia specialist) and Thomas Jefferson (lead author of the book "Marine mammals of the world ').