The Oceanic Whitetip Shark, Carcharhinus longimanus, or Carcharhinus maou is a large pelagic shark. Recent studies show steeply declining populations because its large fins are highly valued as the chief ingredient of shark fin soup and, as with other shark species, the whitetip faces mounting fishing pressure throughout its range.
C. longimanus' most distinguishing characteristics are its long, wing-like pectoral and dorsal fins. The fins are significantly larger than most other shark species, and are conspicuously rounded. The shark's nose is rounded and its eyes are circular, with nictitating membranes.
C. longimanus has a 'typical', although somewhat flattened requiem shark body, often with a mildly humpbacked aspect. It is bronze, brown, bluish or grey dorsally (the colour varies by region), and white ventrally (although it may occasionally have a yellow tint). The Oceanic Whitetip Shark is a medium-sized requiem shark. The largest specimen ever caught measured 4 m (13 ft), an exceptionally large size considering few specimens are known to exceed a length of 3 m (9.8 ft). The maximum reported weight is 170 kg (370 lb). The female is typically larger than the male by 10 cm (3.9 in). Males attain sexual maturity at 1.7 to 1.9 m (5.6 to 6.2 ft) and females about 1.8 to 2 m (5.9 to 6.6 ft). In the Gulf of Mexico in the 1950s, the mean weight of Oceanic Whitetip Sharks was 86.4 kg (190 lb). In the 1990s, the sharks of the species from the same area averaged only 56.1 kg (124 lb).
Most of its fins (dorsal, pectoral, pelvic, and caudal) have white tips (juvenile specimens and some adults may lack these). Along with white tips, the fins may be mottled—and in young specimens can have black marks. A saddle-like marking may be apparent between first and second dorsal fins. The shark has several kinds of teeth—those in the mandible (lower jaw) have a thin serrated tip and are relatively small and triangular (somewhat fang-like). There are between 13 and 15 teeth on either side of the symphysis. The teeth in the upper jaw are triangular, but much larger and broader with entirely serrated edges—there are 14 or 15 along each side of the symphysis. The denticles lie flat and typically have between five and seven ridges.
The shark spends most of its time in the upper layer of the ocean—to a depth of 150 meters (490 ft)—and prefers off-shore, deep-ocean areas. According to longline capture data, increasing distance from land correlates to a greater population of sharks. Occasionally it is found close to land, in waters as shallow as 37 meters (120 ft), mainly around mid-ocean islands such as Hawaii, or in areas where the continental shelf is narrow and there is access to nearby deep water. It is typically solitary, though gatherings have been observed where food is plentiful. Unlike many animals, it does not have a diurnal cycle, and is active both day and night. Its swimming style is slow, with widely spread pectoral fins.
C. longimanus feeds mainly on pelagic cephalopods and bony fish. However, its diet can be far more varied and less selective—it is known to eat threadfins, stingrays, sea turtles, birds, gastropods, crustaceans, and mammalian carrion. The bony fish it feeds on include lancetfish, oarfish, barracuda, jacks, dolphinfish, marlin, tuna, and mackerel. Its feeding methods include biting into groups of fish and swimming through schools of tuna with an open mouth. When feeding with other species, it becomes aggressive.
The oceanic whitetip is usually solitary and slow-moving, and tends to cruise near the top of the water column, covering vast stretches of empty water scanning for possible food sources. Until the 16th century, sharks were known to mariners as "sea dogs" and the oceanic whitetip, the most common ship-following shark, exhibits dog-like behaviour when its interest is piqued: when attracted to something that appears to be food, its movements become more avid and it will approach cautiously but stubbornly, retreating and maintaining a safe distance if driven off, but ready to rush in if the opportunity presents itself. Oceanic whitetips are not fast swimmers, but they are capable of surprising bursts of speed. Whitetips commonly compete for food with silky sharks, making up for its comparatively leisurely swimming style with aggressive displays.