Oceanic whitetip shark

Carcharhinus longimanus is a shark of the family Carcharhinidae, order Carcharhiniformes ^[1]. It lives in the open sea, in tropical and warm temperate waters worldwide, and can be recognised from afar by its long, broad, paddle-like pectoral fins, its tall, rounded first dorsal fin and the white tips of its fins ^[2]. It was once one of the three most abundant oceanic sharks ^[2], but its global category on the IUCN Red List is now Critically Endangered ^[3]. A Peruvian fisheries regulation names it «cazón» ^[4].

Felipe Poey described it in 1861 as Squalus longimanus, from a 1640 mm male from Cuba, and in 1965 the International Commission on Zoological Nomenclature, in its Opinion 723, placed that name on the Official List of Specific Names in Zoology ^[2]. The earliest available name for the species appears to be Squalus maou, by Lesson (1830), but because longimanus was more widely used and is on that official list, Garrick chose in 1982 to keep it, and the FAO catalogue followed him ^[2]. The catalogue also lists Carcharhinus maou and Pterolamiops longimanus as names in use in the preceding years, and its FAO name in Spanish is «tiburón oceánico» ^[2].

It is a large, stocky shark reaching about 3 m or more, with a short, broadly rounded snout and small, circular eyes ^[2]. Its first dorsal fin is very large, with a broad, rounded apex, and starts just in front of the free rear tips of the pectorals; these are huge, elongated, almost straight and round-tipped, and their front edge measures 19 to 29 % of total length ^[2]. The second dorsal is also large, the upper teeth are broad, triangular and strongly serrated, and there are usually 14 rows of teeth in each half of the jaw ^[2].

The back is bronze-grey and the belly white; the tips of the pectorals, first dorsal, pelvics and tail usually carry white mottling, while juveniles also have black blotches or tips on several fins and black saddles on the back that fade in adults ^[2]. Most individuals are under 300 cm, although some giant individuals may reach 350 to 395 cm ^[2]. According to the 2024 NOAA Fisheries review, the largest one measured was 350 cm in total length, in the 1940s, and the 395 cm figure was never confirmed ^[5].

Similar species

• Carcharhinus falciformis: The silky shark also lives in the open sea, but it is slimmer and darker, its first dorsal is moderate in size, falcate and starts behind the pectoral tips, its second dorsal is low with a very long rear tip, and it has no conspicuous markings; the oceanic whitetip instead has a huge, rounded first dorsal, paddle-shaped pectorals and mottled white tips ^[2],[2].

It is found in tropical and warm temperate waters of all three oceans; in the eastern Pacific it has been recorded from southern California to Peru, including the Gulf of California and Clipperton Island ^[2]. It is a species of the surface layer of the open sea that usually lives far from the coast, over bottoms deeper than 184 m and from the surface down to at least 152 m; at times it comes into water only 37 m deep near oceanic islands or where the continental shelf is very narrow ^[2]. It frequents water of 18 to 28 °C, prefers water above 20 °C and is most abundant between 20° N and 20° S ^[2].

It appears in the updated checklist of chondrichthyans from Peruvian waters, based on the 2001 catalogue by Chirichigno and Cornejo ^[6]. It is also among the sharks recorded in Peru's fishery in an analysis of landings from 1950 to 2010 ^[7]. A 2021 study of the eastern Pacific tuna purse-seine fishery, summarised by NOAA Fisheries, predicted higher catches in the boreal spring in several oceanic areas, among them the Humboldt Current between 10° and 16° S and 79° and 87° W ^[5].

In May 2011 satellite tags were fitted to 11 adult sharks off Cat Island, in the Bahamas: during the first month none of them moved more than 500 km away, then they headed for different destinations, with maximum displacements of 290 to 1940 km, and many were back in the Bahamas by about 150 days ^[8]. Of their depth records, 99.7 % fell between the surface and 200 m, but every one of them went down into the mesopelagic zone at some point, on dives that lasted about 13 minutes on average, were commoner at night and reached 1082 m, in water of only 7.75 °C ^[8]. In the central Pacific, one tagged shark covered a straight-line distance of 4285 km in 95 days ^[5].

It is viviparous, with a placenta formed from the yolk sac; litters range from 1 to 15 young, larger the bigger the female, and gestation lasts about a year ^[2]. At birth it measures 60 to 65 cm; males mature at 175 to 198 cm and females at about 180 to 200 cm ^[2].

In the North Pacific, Seki and colleagues read the vertebral rings of 111 males and 114 females taken by tuna longliners between 1967 and 1995; the counts ran from 0 to 11, and they estimated that males and females reach maturity at 4 or 5 years old and 125 to 135 cm precaudal length ^[9]. Young were born at 45 to 55 cm precaudal length; the litters of 97 pregnant females from the North Pacific held 1 to 14 young, with a mean of 6.2, and in the South Pacific 1 to 12, with a mean of 5.5 ^[9]. Births were spread over much of the year, females did not seem to become pregnant again right after giving birth, and the North Pacific nursery area appeared to lie in the open waters of the central Pacific ^[9].

The 2024 NOAA Fisheries review places its theoretical maximum age between about 25 and 36 years, although the highest ages read from vertebrae range from 12 to 19 years ^[5]. A later North Pacific study estimated maturity at 8.5 to 8.8 years in females and 6.8 to 8.9 years in males; females are thought to give birth every other year, after a gestation of 9 to 12 months, with litters of 6 young on average ^[5].

It eats mainly open-sea bony fishes and cephalopods, such as lancetfishes, oarfishes, barracudas, jacks, dolphinfish, tunas, skipjack, marlins and squid, and now and then rays, seabirds, turtles, sea snails, crustaceans, marine mammal carrion and even rubbish ^[2]. Groups have been seen cruising erratically with their mouths wide open in the middle of schools of small tunas while these were rushing at sardines at the surface, and several of the sharks caught there had those tunas in their stomachs ^[2].

It is slow but active by day and by night, and often patrols near the surface with its pectorals spread; when it competes for food with silky sharks of its own size it usually wins, and it is very persistent around any source of food ^[2]. Its trophic level has been estimated at 4.2 out of a maximum of 5, and a stable isotope analysis of vertebrae gave it a mean trophic position of 3.7 ^[5].

The sharks tagged at Cat Island returned to the area after travelling hundreds or thousands of kilometres away, a sign of site fidelity; the authors put forward, as a hypothesis, that they may be drawn by the local abundance of large pelagic prey such as billfishes, tunas and dolphinfish ^[8].

Its global category on the IUCN Red List is Critically Endangered ^[3]. In 2018 the United States listed it as threatened under its Endangered Species Act; it is also on CITES Appendix II and on Annex I of the Sharks Memorandum of Understanding of the Convention on Migratory Species ^[10].

In the eastern Pacific tuna purse-seine fishery it was the second most caught shark after the silky shark, with about 20 % of the shark catch in 2000 and 2001; since 1994 its catches and how often it turns up in sets have fallen so far that they match a population decline of 80 to 95 %, and sharks under 90 cm, which made up 21.4 % of those caught in 1993, have practically vanished ^[5]. Sets on floating objects account for 90 % of its catch in that fishery ^[5].

CITES listed it in Appendix II in 2013, effective from September 2014 ^[5]. Since 2012, through its Resolution C-11-10, the Inter-American Tropical Tuna Commission has banned keeping on board, transhipping, landing, storing or selling the species ^[5]. In Peru, Ministerial Resolution No. 207-2020-PRODUCE, which applied that commission's measures, forbade vessels registered with it to catch, retain, land or store individuals taken in the Convention Area, and asked for those brought alongside to be released unharmed as far as possible ^[11]. Since 2016, moreover, every shark landed in Peru must keep its head and all its fins wholly or partly attached to the body ^[4].

Not medical advice. For a sting, a poisoning or an allergy, seek medical care.

It is regarded as dangerous: a few attacks on swimmers and boats, verified or not, are attributed to it, and in the open sea it has circled divers persistently, with and without bait, coming back again and again even when driven off ^[2]. Bass and colleagues singled it out in 1973 as mainly responsible for many of the deaths among survivors of the sinking of the ship Nova Scotia off Natal, South Africa, during the Second World War; because of its opportunistic feeding, heavy build, strong jaws and teeth and stubborn aggressiveness, the FAO catalogue advises treating it with extreme care ^[2].

It is caught with pelagic longlines, handlines and sometimes trawls, and is used fresh, smoked or dried and salted for human consumption, as well as for its hide, its fins for soup, its liver oil and fishmeal ^[2]. At the same time it is a pest to tuna longliners, because it follows the boats and damages or devours the catch ^[2].

Its meat has little commercial value, but its fins fetch 45 to 85 US dollars per kilo on the international market ^[5]. Between 2015 and 2019 about 2294 kg of its fins that had entered illegally were seized in Hong Kong ^[5].

In Peru, Ministerial Resolution No. 058-2002-PE lists it, as «cazón», among the highly migratory resources of Peru's maritime domain ^[4]. At Cat Island, in the Bahamas, a few shark-diving operators attract it with small amounts of food, and local dive operators reported sightings of tagged sharks ^[8].

It is an open-sea shark that usually lives far from the coast and only comes into shallow water near oceanic islands or where the continental shelf is very narrow ^[2]. In Peru the literature documents it through fishing: it appears among the sharks of the Peruvian fishery in the analysis of landings from 1950 to 2010 ^[7], and a 2021 study of the tuna purse-seine fishery predicted higher catches in oceanic waters of the Humboldt Current between 10° and 16° S ^[5].