Carcharhinus longimanus, the Oceanic Whitetip shark, is in Appendix II of CITES. This means this species requires an export permit or re-export certificate issued by the Management Authority of the State if caught. Furthermore, an export permit may be issued only if the specimen was legally obtained and if the export will not be detrimental to the survival of the species. It is also listed by the IUCN on its Red List of Threatened Species as Vulnerable as its population worldwide may drastically decline unless efforts are put in place to secure its survival.
C. longimanus is a large oceanic shark species, with active and strong swimming capabilities. The longest tracked distance for this species was 1,226 km, and the maximum speed was 32.4 km/day (Kohler et al., 1998). It was further reported that only part of the tagged animals for the study undertook long-distance movements, whereas the other part remained within the vicinity of the Bahamas. Tolotti et al. (2015) showed that several individuals presented a strong site fidelity returning to the place they were tagged after traveling thousands of kilometers. The species exhibits higher site fidelity in areas where large pelagic teleosts are abundant, for feeding purposes (Madigan et al., 2015). It feeds close to the top of the marine food web, occupying a top predator position along with other large pelagic teleost species (Cortés, 1999; Madigan et al., 2015). It is a circumtropical species and the only true oceanic species within the Carcharhinus-genus (CITES, 2013). It is considered to be one of the most widespread shark species, ranging across all tropical and subtropical waters (Baum et al., 2015). C. longimanus can easily be distinguished from other shark species by its large, rounded fins. Especially the pectoral fins are long, and paddle-shaped. It also presents white tips on the pectoral and caudal fins.
The oceanic whitetip has been reported from waters between 15ºC and 28ºC, however the species exhibits a strong preference for the surface mixed layer in water with temperatures above 20°C. It occurs in both coastal and pelagic zones, utilizing shallow habitats from surface waters to a depth of 20 meters. However, Young et al. (2016) report C. longimanus as a truly oceanic species usually found far offshore in the open sea. It can tolerate colder waters down to 7.75°C for short periods in deep dives into the mesopelagic zone below the thermocline (>200 m), presumably for foraging (Howey-Jordan et al. 2013; Howey et al. 2016).
C. longimanus can reach a maximum size of 3.46m, with most specimens measuring between 1.50 and 2.05 m (Lessa et al., 1999; CITES, 2013; D’Alberto et al., 2016; Joung et al., 2016). It is estimated it reaches maturity (50% maturity) at an age of 8.9 years for males and 8.8 years for females in the western North Pacific. The estimated longevity of the species is 25 years. It is a viviparous species, giving birth to live young after a gestation period of 12 months, the female producing a litter of 1 to 14 pups (mean: 6). Both Seki et al. (1998) and Lessa et al. (1999) report a positive correlation between female size and litter size. Although the life history parameters of this species are consistent with intermediate among shark species their specific biology indicate that it is a species with a low resilience to fishing and a low productivity with a high catchability due to its preference for surface water and presence in tropical latitudes where tuna fisheries are most active (FAO, 2012).
Oceanic Whitetip sharks have been caught in both target fisheries and as bycatch in almost all parts of their range, they are particularly vulnerable to capture in pelagic longline, purse seine and driftnet fisheries. Overall, evidence (both quantitative and qualitative) suggests that while the oceanic whitetip shark was once considered to be one of the most abundant and commonly encountered pelagic shark species wherever it occurred, this oceanic species has likely undergone population abundance declines of varying magnitudes throughout its global range. Where more robust information is available, declines in oceanic whitetip shark abundance range from 86% to greater than 90% in some areas of the Pacific Ocean (with declines observed across the entire basin), and between 57%-88% in the Atlantic and Gulf of Mexico (Young et al, 2016).
Based on logbook data of the U.S. pelagic longline fleet, C. longimanus has experienced a 70% population decline between 1992 and 2000 within the Northwestern Atlantic Ocean and Gulf of Mexico (Baum et al. 2003). Within the tropical western and central Pacific Ocean, C. longimanus is among the four most caught species in the tuna longline fishery and is the second most caught species (after silky sharks, Carcharhinus falciformis) in the tuna purse seine fishery (Williams, 1999). Santana et al. (2004) looked at the population in North-Eastern Brazil and found a rate of decline of 7,2% since the 1990’s due to high natural mortality in the first year of life combined with unsustainable fishing pressure. This resulted in a 50% drop in population over a 10-year time. The only population that currently shows a stable trend, based on standardized CPUE observer data, is the Northwest Atlantic. Although these studies indicate that large pelagic sharks (including C. longimanus) declined over the past decades, the magnitude of these declines is unclear, due to sampling differences and origin of the data. Furthermore, the consequences of C. longimanus removal have not been published, and the loss of predatory sharks can have cascading effects throughout marine ecosystems (Meyers et al., 2007).
Some studies have been conducted on survival of this species after capture indicating that for long-line fisheries this species have a potential for high survival after release. Gallagher et al. (2014) found an at vessel survival percentage of 77,3% in Atlantic longline fisheries which would put this species in the highest survival category for shark species. Survival in purse seine and drift net fisheries is negligible as the sharks cannot keep swimming after capture and pressure in the net will cause internal damage.
C. longimanus is a preferred species in the shark fin trade in the Hong Kong fin market as its fins are large and deemed of prime quality (Young et.al 2016), although the meat is generally of low value. Fins from this species are one of the most distinctive and common products in the Asian shark fin trade.
Reduction of threats
There is still a lack of understanding of the basic data needed to understand the life history, habitat utilisation and migration patterns of this species. A better understanding of the specific habitat types and characteristics that influence the abundance of these sharks within those habitats is needed to determine the effects of fishing activities on habitat suitability for oceanic whitetip sharks. The comparison in management measures between Regional Fisheries Management Organisations (RFMOs) illustrates that alignment of policy between areas is needed to improve the effective management of this species. It has also been reported that the migratory behaviour of the species can be an advantage to mitigate the risks climate change poses to the species as it is less dependent on one discrete geographic area.
|Instruments de la CMS||Requins (2018)|
|IUCN Status||Critically endangered|
|Date of entry in Appendix I||2020|
|Pays||Angola, Anguilla (UK), Antigua and Barbuda, Aruba (Netherlands), Australia (New South Wales, Northern Territory, Queensland, South Australia, Western Australia), Bahamas, Bangladesh, Barbados, Belize, Benin, Bermuda (UK), Bonaire, Saint Eustatius and Saba (Netherlands), Bonaire, Saint Eustatius and Saba (Netherlands), Bouvet Island (Norway), Brazil, British Virgin Islands (UK), Brunei Darussalam, Cabo Verde, Cambodia, Cameroon, Cayman Islands (UK), Chile, China, Christmas Island (Australia), Cocos (Keeling) Islands (Australia), Colombia, Comoros, Cook Islands, Costa Rica, Cuba, Curaçao (Netherlands), Côte d'Ivoire, Democratic Republic of the Congo (Kinshasa), Djibouti, Dominica, Dominican Republic, Ecuador, Egypt, El Salvador, Equatorial Guinea, Eritrea, Faroe Islands (Denmark), Fiji, French Guiana (France), French Polynesia, French Southern and Antarctic Lands, Gabon, Gambia, Ghana, Grenada, Guadeloupe (France), Guatemala, Guinea, Guinea-Bissau, Guyana, Haiti, Heard Island and McDonald Islands (Australia), Honduras, India, Indonesia, Israel, Jamaica, Japan, Jordan, Kenya, Liberia, Madagascar, Malaysia, Maldives, Marshall Islands, Martinique (France), Mauritania, Mauritius, Mexico (Baja California, Baja California Sur, Campeche, Chiapas, Colima, Guerrero, Jalisco, Michoacán, Nayarit, Oaxaca, Quintana Roo, Sinaloa, Sonora, Tabasco, Tamaulipas, Veracruz, Yucatán), Montserrat (UK), Morocco, Myanmar, Nauru, New Caledonia (France), Nicaragua, Niger, Niue, Oman, Pakistan, Palau, Panama, Papua New Guinea, Peru, Philippines, Pitcairn Islands (UK), Portugal (https://www.cms.int/sharks/sites/default/files/document/cms_sharks-mos3_doc.9.1.1_rev1_brazilian-proposal_oceanic-whitetip-shark_e.pdf), Puerto Rico (USA), Réunion (France), Saint Helena, Ascension and Tristan da Cunha (UK), Saint Kitts and Nevis, Saint Lucia, Saint Martin (France), Saint Vincent and the Grenadines, Samoa, Saudi Arabia, Senegal, Seychelles, Sierra Leone, Singapore, Sint Maarten (Netherlands), Slovenia, Solomon Islands, Somalia, South Africa (KwaZulu-Natal, Northern Cape Province, Western Cape), Spain (Canary Island), Sri Lanka, Sudan, Suriname, São Tomé and Príncipe, Thailand, Togo, Tokelau (New Zealand), Tonga, Trinidad and Tobago, Turks and Caicos Islands (UK), Tuvalu, United Republic of Tanzania, United States of America (Alabama; American Samoa; California, Connecticut, Delaware, District of Columbia, Florida, Georgia, Guam; Hawaiian Is., Johnston I., Louisiana, Maine, Maryland, Massachusetts, Mississippi, New Hampshire, New Jersey, New York, North Carolina, Northern Mariana Islands; Rhode Island, South Carolina, Texas, Virginia; Wake Is), Uruguay, Vanuatu, Venezuela, Viet Nam|
Pas de photo pour Carcharhinus longimanus
|Anglais||Oceanic whitetip shark|
|Nom scientifique||Carcharhinus longimanus|
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