The Common Dolphin Delphinus delphis is a small dolphin with an elaborate hourglass pattern on the flanks, consisting of a dark cape forming a ‘V’ under the dorsal fin, a white underside, a pale grey tail stock and yellow flanks forward of the dorsal fin. Adults measure 1.7-2.4 metres in length (Carwardine, 1995).
The JNCC Atlas (Reid et al, 2003) indicates that the Common Dolphin is a scarce species off northeast England, with very few records in the North Sea over the period 1990 to 2002. Too few were seen to estimate summer abundance in 2005 for Northern and central North Sea areas from the SCANS II survey (International Council for the Exploration of the Sea (ICES), 2008). Davis and Muir in Foster-Smith (Foster-Smith, 2000) indicates that historically this is a rare species in the region, including only a number of anonymous reports received by Sunderland University in June 1989. Mennell and Perkins do not mention this species at all.
During the North East Cetacean Project (NECP) winter transect surveys in early 2010, there were two sightings of probable and definite single Common Dolphins both in the Farne Deeps, representing the only dolphins recorded on the surveys. The proximity of the two sightings suggests that possibly just one animal was involved and the occurrence of this warm water oceanic species in the cold waters of the central North Sea during the winter months, particularly given the severity of the winter of 2009/2010, was wholly unpredicted and quite remarkable. On the publication of the NECP report (Brereton et al, 2010), the media seized on the observations of this species off Northumberland as evidence of global warming and a rise in sea surface temperatures, but subsequent years have not supported that hypothesis.
There were four casual sightings over the period 2003 to 2009, with five animals off Tynemouth in early July 2009, from a transect survey on the Newcastle-Ijmuiden ferry and three sightings of three or four animals off Cullercoats in July and August 2004 by commercial fishermen, confirming that the species is rarely recorded from coastal watchpoints. However, the Common Dolphin is more of an offshore species than the Bottlenose Dolphin Tursiops truncatus, Harbour Porpoise Phocoena phocoena and White-beaked Dolphin Lagenorhynchus albirostris in the summer months, so sighting rates from coastal waters may be less representative of the species’ wider status in the region, and the ongoing offshore survey work carried out by the NECP may reveal that the species is regular, if scarce, out of sight of land-based observers. Like Risso’s Dolphin Grampus griseus, this species seems to be a recent addition to the marine megafauna of our region, and it seems likely that the number of sightings will increase.
Written by Martin Kitching (last updated Nov 12)