Oceanic whitetip shark  (Carcharhinus longimanus)

Classified as Vulnerable (VU) on the IUCN Red List (1).

Considered one of the five most dangerous sharks in the world, the oceanic whitetip shark has a stocky build, a short, bluntly-rounded snout, and incredibly powerful jaws (3) (4). This voracious predator grips its prey with the pointed teeth of the lower jaw, serrated only at the tip, while the broader, triangular, serrated teeth in the upper jaw are used to saw, cut and tear the flesh (3) (4). The first dorsal fin is distinctively large and rounded, and the paddle-like pectoral fins are very long and wide (3). The oceanic whitetip shark is so named because the tips of its pectoral, first dorsal, pelvic, and caudal fins are often white or show white mottling (2) (3) (4). These markings are usually black on young individuals below 1.3 meters, and a dark, saddle-shaped marking may also be present between the first and second dorsal fin (3) (5). Depending upon geographic location, the body colour may be brown, grey, beige or bronze, sometimes bluish, while the stomach is usually white, occasionally with a yellow tinge (2) (4).

This widely distributed species can be found from Maine, U.S., south to Argentina in the Western Atlantic Ocean, including the Caribbean and Gulf of Mexico, and from Portugal to the Gulf of Guinea, in the Eastern Atlantic, possible including the Mediterranean. In the Indo-Pacific, this shark inhabits waters from the Red Sea and East Africa to Hawaii, Samoa, Tahiti and the Tuamoto Islands. In the Eastern pacific the distribution includes waters from southern California, U.S., south to Peru, including the Galapagos (2) (3).

This shark is an oceanic, epipelagic species found mainly in offshore, tropical and warm-temperate waters (6), although on occasion in shallower waters near land, usually near oceanic islands (3). Found from the surface to depths of at least 150 m (2).

The diet of the oceanic whitetip shark primarily consists of bony fishes such as tuna and mackerel, but also includes stingrays, sea turtles, sea birds, squid, crustaceans, mammalian carrion (dead whales and dolphins), and occasionally even rubbish that is disposed in the sea (3). The species is usually solitary, but will occasionally congregate in groups during ‘feeding frenzies’ where food is plentiful (4), such as around whale carcasses (7). However, if other shark species are encountered competing for the same food source, the oceanic whitetip shark usually dominates over them, and may become aggressive (3) (4). This shark is often accompanied by remoras, dolphin fishes and pilot fishes, and reportedly demonstrates an unusual association with the shortfin pilot whale (Globicephala macrorhynchus) in Hawaiian waters (2) (3). Although the exact reason for this shark swimming along with pods of pilot whales is unknown, it is suspected that oceanic whitetip sharks are following them to sources of squid, which the pilot whales are extremely efficient at locating (3).

This species mates during the early summer in the north-western Atlantic and the south-western Indian Ocean, and females give birth to 1 to 15 live young approximately a year later (3) (6). Reproduction is viviparous, with live young being born after being nourished by a placental yolk-sac that is attached to the uterine wall by umbilical cords (3). Sexual maturity is attained at an age of six to seven years for both sexes (3).

The oceanic whitetip shark suffers from fishing pressure throughout most of its range, with large numbers being caught as bycatch by tuna and other pelagic fisheries (1) (3). The shark’s large fins are highly prized in international trade, being sold to the Far East to make shark-fin soup, but the remainder of the carcass is often discarded (1). Although classified as Vulnerable overall, this species has been assessed as Critically Endangered by the IUCN in the Northwest and Western Central Atlantic, due to massive declines in reported catch quantities indicating significant population declines (1). However, catches in international waters elsewhere are often inadequately monitored, and there is simply insufficient data to asses the real impact fisheries are having (1).

Efforts are currently being made to collect essential data on population declines from regions where demographic trends are poorly understood. While the information gained will certainly help guide future conservation measures, truly effective conservation and management will depend upon international cooperation, and acceptance of a collective responsibility to help protect this magnificent oceanic shark (1).

For more information on the oceanic whitetip shark see:

• Biological Profile, Ichthyology Department, Florida Museum of Natural History:
  www.flmnh.ufl.edu/fish/Gallery/Descript/OceanicWT/OceanicWT.html

For further information on the conservation of sharks and rays see:

• Save Our Seas Foundation:
  http://www.saveourseas.com
• Project Aware:
  http://www.projectaware.org/

• The Shark Foundation:
  www.shark.ch
• The Shark Trust:
  www.sharktrust.org

• Bycatch: in the fishing industry, the part of the catch made up of non-target species.
• Caudal fin: the tail fin of fish.
• Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
• Epipelagic: the oceanic zone extending from the surface to about 200 meters, where enough light penetrates to allow photosynthesis.
• Oceanic: relating to, occurring in or inhabiting the open oceans.
• Pectoral fins: in fish, the pair of fins that are found one on each side of the body just behind the gills. They are generally used for balancing and braking.
• Pelagic: inhabiting the open oceans rather than inshore waters.
• Pelvic fins: in fish, the pair of fins found on the underside of the body.
• Viviparous: giving birth to live offspring that develop inside the mother’s body.

1. IUCN Red List (September, 2007)
   http://www.redlist.org
2. FishBase (May, 2006)
   http://www.fishbase.org
3. Florida Museum of Natural History: Ichthyology (May, 2006)
   http://www.flmnh.ufl.edu/fish/Gallery/Descript/OceanicWT/OceanicWT.html
4. Animal Diversity Web (May, 2006)
   http://animaldiversity.ummz.umich.edu/site/index.html
5. Marine Themes: The world's largest marine wildlife image database (May, 2006)
   http://www.marinethemes.com/oceanicshark.html
6. Shark Foundation (May, 2006)
   http://www.shark.ch/Database/Search/species.html?sh_id=1010
7. The Elasmodiver: Shark and Ray Field Guide (May, 2006)
   http://www.elasmodiver.com/oceanic_white_tip_shark.htm