A note on the distribution of short-beaked common dolphins, Delphinus delphis, observed during the 2007 T-NASS (Trans North Atlantic Sightings Survey)

T-NASS was to estimate the abundance of cetacean populations in the Northern North Atlantic from survey data collected during summer 2007, under the auspices of NAMMCO, adding to the series of North Atlantic Sightings Surveys (NASS) thus forming a 20-year time series. T-NASS was coordinated with the European CODA survey and the American SNESSA survey. Line transect methods and/or cue counting, with when possible double platform design, were used to collect visual data. Passive acoustic data were also collected from five of the vessels. With the participation of Canada, Greenland, Iceland, the Faroes, Norway, and the Russian Federation, as well as observers on fishery surveys, a trans North Atlantic survey was achieved for the first time with 57,000 nm of transects in effort in an area of about 1.5 million nm², ranging from the Eastern Barents Sea to the east coast of Canada, and from 78ºN to 52ºN in the east and 61ºN to 42ºN in the west. Cetacean encounters totaled over 3.900 with 22 cetacean species identified. Short-beaked common dolphins came in 6th position in terms of sightings events (6%), with 90% made off Canada, where sighting conditions were very good. Off Canada, their distribution ranged from about 56.9º to 42.4ºN, but they were more frequent on the Scotian Shelf and then off Southern Newfoundland, with most sightings occurring in the mid- and outer-shelf areas, rather than near shore. In the North East Atlantic, where survey conditions were generally poor, common dolphins were not observed by dedicated surveys, even in areas where they used to be commonly observed in previous NASS. The few common dolphin sightings were made from the fishery survey MAR-ECO moving towards or on the mid- Atlantic ridge. Their distribution (55.2° to 48.8ºN and 8.1° to 31.2ºW) falls within the range previously described.