Found in sub-Arctic and cool temperate waters of the North Atlantic and North Pacific (5), the harbour porpoise is typically a species of coastal areas, although it also occurs over most of the European continental shelf (4). In the UK, seasonal concentrations occur between July and October off western and south-western Ireland, west Wales, the west of Scotland, around Shetland and Orkney as well as around north-east Scotland (4). This species used to occur in the south coast of England and southern parts of the North Sea, but it is now rare in these waters (4).