Distribution and abundance of killer whales in the North East Atlantic

We present a review of 3,787 sightings from across the NE Atlantic from 1970-2007. In light of a large migration shift in the late 1960's by the Norwegian spring spawning herring Clupea harengus stock, a key prey species, we compare these sightings with whaling catch data from 1938 to 1967. The two datasets show a similar distribution pattern suggesting that there are populations of killer whales in the NE Atlantic that do not follow the NSS herring migration. We estimate abundance using data from several large-scale line transect North Atlantic Sighting Surveys (NASS) in 1987, 1989, 1995 and 2001, which covered mainly the eastern NE Atlantic between the Faroe Islands and East Greenland. There was high inter-annual variability in these estimates, ranging from 4,413 to 26,774; we discuss possible reasons for this variability in abundance estimates.