Oceanic whitetip shark

The oceanic whitetip shark, or lesser white shark, was described in 1831 by naturalist René-Primevère Lesson, who named the shark Carcharhinus maou.[4] It was next described by Cuban Felipe Poey in 1861 as Squalus longimanus.[4] The name Pterolamiops longimanus has also been used. The species epithet longimanus refers to the size of its pectoral fins (longimanus translates from Latin as "long hands").[5] The oceanic whitetip shark has many common names in English: Brown Milbert's sand bar shark, brown shark, nigano shark, oceanic white-tipped whaler, and whitetip shark.[5]

The rules of the International Commission on Zoological Nomenclature are that in general the first-published description has priority; therefore, the valid scientific name for the oceanic whitetip shark should be Carcharhinus maou. However, Lesson's name remained forgotten for so long that Carcharhinus longimanus remains widely accepted.[6]

The oceanic whitetip is found globally in deep, open oceans, with a temperature greater than 18 °C (64 °F),[3] although exceptionally it occurs in water as cold as 15 °C (59 °F).[1] It prefers waters between 20 and 28 °C (68–82 °F) and tends to withdraw from areas when temperatures fall outside of these limits.[1][6] It was once extremely common and widely distributed, and still inhabits a wide band around the globe; however, recent studies suggest that its numbers have drastically declined.[7] An analysis of the US pelagic longline logbook data between 1992 and 2000 (covering the Northwest and Western Central Atlantic) estimated a decline of 70% over that period.[1]

It is found worldwide between 45°N and 43°S latitude.[3] In September 2004, a 2.3 m (7.5 ft) vagrant oceanic whitetip shark was seen in the brackish waters of Gullmarsfjorden in Sweden; it died shortly after.[8][9] This is the only North European record and far north of its usual range limit.[8]

The shark spends most of its time in the upper layer of the ocean—to a depth of 150 m (490 ft)[3]—and prefers off-shore, deep-ocean areas. According to longline capture data, increasing distance from land correlates to a greater population of sharks.[5] Occasionally, it is found close to land, in waters as shallow as 37 m (120 ft), mainly around midocean islands such as Hawaii, or in areas where the continental shelf is narrow with access to nearby deep water.[6]

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.[5]

Oceanic whitetip jaws

C. longimanus has a 'typical', although somewhat flattened requiem shark body, often with a mildly humpbacked aspect. It is grey-bronze dorsally and white ventrally, with some mottling on the fins.[6] 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 2.0 m (5.9 to 6.6 ft).[5][6] 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).[10]

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 young specimens can have black marks. A saddle-like marking may be apparent between first and second dorsal fins.[5] 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). Between 13 and 15 teeth are on either side of the symphysis. The teeth in the upper jaw are triangular, but much larger and broader with entirely serrated edges—14 or 15 occur along each side of the symphysis.[5] The denticles lie flat and typically have between five and seven ridges.[5]

Oceanic whitetip photographed at the Elphinstone reef, Red Sea, Egypt, accompanied by pilot fish

It is typically solitary, though gatherings have been observed where food is plentiful.[6] Unlike many animals, it does not have a diurnal cycle, and is active both day and night.[5] 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. They have, however, been observed to breach out of the water.[5][11] Despite its habitual isolation from members of its own species, pilot fish, dolphinfish, and remora may accompany it.[5] Evidence in the form of sucker scars on the skin of an individual filmed off Hawaii indicate that the species may also dive deep enough to battle with giant squid.[12] Until the 16th century, sharks were known to mariners as "sea dogs"[13] and the oceanic whitetip, the most common ship-following shark.[6]

C. longimanus feeds mainly on pelagic cephalopods and bony fish.[3] 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, mahi-mahi, marlin, tuna, and mackerel. Its feeding methods include biting into groups of fish and swimming through schools of tuna with an open mouth. When whaling took place in warm waters, oceanic whitetips were the most common scavengers of floating carcasses. Whitetips commonly compete for food with silky sharks, making up for its comparatively leisurely swimming style with aggressive displays.[6] They are known to trail pilot whales since they feed on squid.[14]

Groups often form when individuals converge on a food source. They are recorded to segregate by both sex and size.[6] Oceanic whitetips gather in large numbers off Cat Island, Bahamas from winter to spring, due to the abundance of large bony fish.[14]

Mating season is in early summer in the northwest Atlantic Ocean and southwest Indian Ocean, although females captured in the Pacific have been found with embryos year round, suggesting a longer mating season there.[6] The shark is viviparous—embryos develop in utero and are fed by a placental sac. Its gestation period lasts nine months to one year.[15][16] In the northwest Atlantic, shark pups are born 65–75 cm (26–30 in) long while off South Africa, birth length is 60–65 cm (24–26 in) long.[15] In the Pacific Ocean, newborns average 45–55 cm (18–22 in) long, and number two to fourteen per litter.[16]

In one population off Brazil, sharks were recorded to grow an average of 25.2 cm (9.9 in) in one year, reducing to 13.6 cm (5.4 in) per year up to four years and then 9.7 cm (3.8 in) in their fifth year. Both sexes reached maturity at 180–190 cm (71–75 in) between the ages of six and seven and continued to grow at 9.10 cm (3.58 in) per year.[17] The average length of maturity for sharks averages in the greater equatorial and southwestern Atalntic is 170 cm (67 in) for females and 170–190 cm (67–75 in) for males.[18] In the Pacific, sharks appear to mature at four to five years and may live up to eleven years.[16]

Oceanic whitetip with a rusty fish hook in its mouth

The oceanic whitetip is a commercially important species for its fins, meat, and oil. It is eaten fresh, smoked, dried, and salted and its hide is used for leather.[6] It is subject to fishing pressure throughout virtually its whole range,[1] although it is more often taken as bycatch than by design, since it is drawn to longline bait that is intended for other species.[6]

Oceanographic researcher Jacques Cousteau described the oceanic whitetip as "the most dangerous of all sharks".[19] Author and big-game fisherman Ernest Hemingway depicted them as aggressive opportunists that attacked the catch of fishermen.[20] After the USS Indianapolis was torpedoed on 30 July 1945, most sailors who survived the sinking reportedly died from exposure to the elements rather than from shark bites.[21] However, according to survivor accounts published in several books about sharks and shark attacks, potentially hundreds of the Indianapolis crew were eventually killed by sharks before a plane spotted them on the 5th day after the sinking. Oceanic whitetips are believed to have been responsible for most if not all of those attacks.[22][23] Also during World War II, the RMS Nova Scotia, a steamship carrying about 1,000 people near South Africa, was sunk by a German submarine. One hundred and ninety-two people survived; many deaths were attributed to the whitetip.[24] Subsequently, the species is recorded to have attacked 21 people between 1955 and 2020, including of nine divers, eight swimmers, two fisherman, one shipwrecked person and one fallen pilot. Five of these attacks were fatal.[25]

In Egypt in 2010, one oceanic whitetip was implicated in several bites on tourists in the Red Sea near Sharm El Sheikh, resulting in one death and four injuries to humans. Accumulating evidence revealed this shark to have been conditioned to being hand fed.[26][27] In October 2019, an oceanic whitetip shark brutally attacked a female snorkeler off Mo'orea, French Polynesia. The person survived, and based on eyewitness reports and examinations of the bites, the shark may have been acting predatory.[25]

The oceanic whitetip has fared better in captivity than other large sharks of the open ocean. Among five recorded captive oceanic whitetips, the three with time records all lived for more than a year in captivity. One of these, a female in Monterey Bay Aquarium's Outer-Bay exhibit, lived for more than three years before dying in 2003, during which it grew 0.3 m (1 ft).[28][29] The two remaining lack a time record, but grew about 0.5 m (1.6 ft) during their time in captivity.[28]

As of 2019, the IUCN Red List list the oceanic whitetip shark as Critically Endangered, as their numbers appear to have decreased in every ocean region they inhabit. While their total global population is unknown, they are estimated to have declined by around 98 percent "with the highest probability of >80% reduction over three generation lengths (61.2 years).".[1]

In 1969, Lineaweaver and Backus wrote of the oceanic whitetip: "[it is] extraordinarily abundant, perhaps the most abundant large animal, large being over 100 pounds [45 kg], on the face of the earth".[30] Little further population study occurred until 2003, when the numbers were estimated to have dropped by as much as 70% in the Northwest and Western Central Atlantic between 1992 and 2000.[1] Another study focusing on the Gulf of Mexico, using a mix of data from US pelagic longline surveys from the mid-1950s and observations from the late 1990s, estimated a decline in numbers in this location of 99.3% over this period.[7] However, changes in fishing practices and data collection methods complicate estimates.[31] According to a January 2021 study in Nature which studied 31 species of sharks and rays, the number of these species found in open oceans had dropped by 71 per cent in around 50 years. The oceanic whitetip was included in the study.[32][33]

Under the 1995 UN Agreement on the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks, coastal and fishing states are specifically required to adopt measures to conserve listed species, but little progress is visible on the oceanic whitetip.[1] From 3 January 2013, the shark was fully protected in New Zealand territorial waters under the Wildlife Act 1953.[34][35] The New Zealand Department of Conservation has classified the oceanic whitetip shark as "Migrant" with the qualifier "Secure Overseas" under the New Zealand Threat Classification System.[36]

In March 2013, the oceanic whitetip was added to Appendix II of CITES meaning the species (including parts and derivatives) require CITES permits for international trade.[37] On 30 January 2018, NOAA Fisheries published a final rule to list the oceanic whitetip shark as a threatened species under the United States Endangered Species Act (ESA) (83 FR 4153).[38]

• Blacktip reef shark
• List of sharks
• List of threatened sharks
• Outline of sharks
• Shark attack

Wikimedia Commons has media related to Carcharhinus longimanus.

• "Introducing an ongoing study of the Oceanic Whitetip Shark in the Red Sea". longimanus.info.
• Oceanic Whitetip shark Carcharhinus longimanus at marinebio.org
• Photos of Oceanic whitetip shark on Sealife Collection