Striped dolphin  (Stenella coeruleoalba)

Classified as Least Concern (LC) on the IUCN Red List (1), and listed on Appendix II of CITES (3). It is also listed on Appendix II of the Convention on Migratory Species (4). 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 (5).

With the classic dolphin shape, the striped dolphin’s most remarkable feature is the distinctive pattern of blue and white stripes along the body. It is mainly blue with a white to light grey stripe following the spine. The sides are darker than the belly (4). The beak is fairly long and prominent, the dorsal fin is tall, and the flippers are long and narrow with black stripes (6)

The striped dolphin is found in all temperate and tropical waters, throughout the Atlantic Ocean, Pacific Ocean, Indian Ocean, Mediterranean Sea and Black Sea (1).

The striped dolphin inhabits temperate and tropical pelagic waters (1).

A highly gregarious animal, the striped dolphin may associate in schools of over 1000, but is more usually seen in same-age groups of 100 to 500 individuals (6). It is a very active swimmer, performing leaps and breaching frequently. Communication between striped dolphins is by clicks and whistles (7).

The striped dolphin feeds opportunistically, but the diet is mainly composed of cephalopods, crustaceans and fish, particularly lantern fish. The diet varies with geographical location (8).

The mating season also varies with region. Males reach sexual maturity between 7 and 15 years and females between 5 and 13 years. The gestation period lasts 12 to 13 months and results in a single calf measuring less than a metre and weighing just 11 kilograms. The calf will stay with the female in a ‘mothers-and-calves’ school until it is weaned at 16 months. Females typically give birth every four years (6) (9).

Once a substantial threat, by-catch has been reduced from 14,000 striped dolphins a year between 1950 and 1969 in the western Pacific, to a current incidental catch of 2,000 to 4,000 individuals. Fishermen kill dolphins caught in their nets as they present competition for fish (7). Hunting has also been known to take place, particularly in Japan, but is not considered a major threat, and Japan has voluntarily reduced its catch. Water pollution as a result of the release of heavy metals causes lung disease, and the over-fishing of anchovies has harmed populations in some areas (4). In the Mediterranean Sea, a morbillivirus caused the death of more than 1,000 animals between 1990 and 1992. The epidemic was possibly caused by poor environmental conditions (1).

A UK Biodiversity Action Plan priority species, the striped 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 (5). The Agreement on the Conservation of Small Cetaceans in the Baltic and North Seas (ASCOBANS) has been signed by 7 European Countries, this includes the UK. Provision is made under this agreement to set up protected areas, promote research and monitoring, pollution control and increase public awareness (5).

For further information on the striped dolphin see:

• The Convention on Migratory Species:
  www.cms.int/reports/small_cetaceans/data/S_ceoruleoalba/s_coeruleoalba.htm

• Beak: In cetacea (whales and dolphins): the elongated forward part of the head, comprising the lower jaw and upper jaw or ‘rostrum’.
• By-catch: in the fishing industry, the part of the catch made up of non-target species.
• Cephalopoda/ Cephalopod: from the Greek for ‘head-foot’, a class of molluscs that occur only in marine habitats. All species have grasping tentacles, and either an internal or external shell. Includes nautiloids, cuttlefish, squids, octopuses, and extinct ammonites and belemnites.
• Crustacea: diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.
• Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
• Gestation: the state of being pregnant; the period from conception to birth.
• Pelagic: inhabiting the open oceans.

1. IUCN Red List (November, 2008)
   http://www.iucnredlist.org
2. Whale and Dolphin Conservation Society (November, 2004)
   http://www.wdcs.org/species_guide.php
3. CITES (November, 2004)
   http://www.cites.org
4. Convention on Migratory Species (November, 2004)
   http://www.cms.int/reports/small_cetaceans/data/S_ceoruleoalba/s_coeruleoalba.htm
5. UKBAP (June, 2008)
   http://www.ukbap.org.uk/species.aspx
6. Archer, F. and Perrin, W. (1999) Stenella coeruleoalba. Mammalian Species, 603: 1 - 9.
7. Animal Diversity Web (June, 2008)
   http://animaldiversity.ummz.umich.edu/site/accounts/information/Stenella_coeruleoalba.html
8. Wuertz, M. and Marrale, D. (1993) Food of striped dolphin, Stenella coeruleoalba, in the Ligurian Sea. Journal of the Marine Biological Association of the United Kingdom, 73 (3): 571 - 578.
9. Calzada, N., Aguilar, A., Lockyer, C. and Grau, E. (1997) Patterns of growth and physical maturity in the western Mediterranean striped dolphins Stenella coeruleoalba. Canadian Journal of Zoology, 75 (4): 632 - 637.