Atlantic white-sided dolphin  (Lagenorhynchus acutus)

Classified as Least Concern (LC) on the IUCN Red List (1). All cetaceans (whales and dolphins) are listed on Annex A of EU Council Regulation 338/97; they are therefore treated by the EU as if they are included in CITES Appendix I, so that commercial trade is prohibited. In the UK all cetaceans are fully protected under the Wildlife and Countryside Act, 1981 and the Wildlife (Northern Ireland) Order, 1985 (3).

The Atlantic white-sided dolphin is a large, robust species (4), which is easily recognised by the obvious yellow patch towards the rear of the flanks (2). The common name refers to the pale band on each side situated below the dorsal fin (2). This species is often confused with the white-beaked dolphin, but the Atlantic white-sided dolphin has a much darker back (5). It may also be confused with the common dolphin because of the similar pattern (grey, white, black and yellow), but it lacks the distinctive hourglass pattern (6).

This species inhabits cool temperate and sub-arctic waters of the North Atlantic (4). In UK waters, main concentrations occur around the Hebrides, the Northern Isles and northern areas of the North Sea (3). It is sometimes seen off the west of Ireland, and in the south-west approaches of the English Channel (3).

You can view distribution information for this species at the National Biodiversity Network Gateway.

The Atlantic white-sided dolphin tends to prefer depths of between 40 and 270 metres in the vicinity of the continental shelf where the surface temperature is in the range of 6 to 20 degrees Celsius (5). It seems to prefer areas with high seabed relief, and along the continental shelf (6).

This species is a very social and active animal; it forms groups of up to several hundred individuals (5), and tends to readily mix with other species of cetaceans (whales and dolphins) (4). This fast-swimming species can often be seen breaching (clearing the water), bow-riding (riding on the bow-wave at the front of boats and even large whales), and splashing the tail flukes noisily onto the surface of the water (4). They feed on a range of fish species as well as squid (2). Strandings of both individuals and of groups are a fairly common occurrence (4). A single calf is typically produced in June or July after a gestation period of around ten months (7). At birth the calf measures somewhere in the region of 1.1 metres in length (2), and will be weaned by 18 months of age (7).

Threats to the Atlantic white-sided dolphin include hunting, chemical pollution, environmental change and entanglement in fishing nets, which results in drowning (4).

A UK Biodiversity Action Plan priority species, the Atlantic white-sided dolphin is protected in UK waters by the Wildlife and Countryside Act 1981 and the Wildlife (Northern Ireland) Orders, 1985; it is illegal to intentionally kill, injure, or harass any cetacean (whale or dolphin) species in UK waters (3). The Agreement on the Conservation of Small Cetaceans in the Baltic and North Seas (ASCOBANS) has been signed by seven European countries, including the UK. Provision is made under this agreement to set up protected areas, promote research and monitoring, pollution control and increase public awareness (3).

The UK Biodiversity Action Plan for this species is available at UK BAP.

View information on this species at the UNEP World Conservation Monitoring Centre.

There may be further information about this species available via the National Biodiversity Network Gateway.

To contribute to the conservation of dolphins see:

• Whale and Dolphin Conservation Society:
  www.wdcs.org