Oceanic whitetip shark

The oceanic whitetip shark (Carcharhinus longimanus) is one of several species of shark that are on the red list of the International Union for the Conservation of Nature (IUCN) as being under threat in the wild. This particular species is listed as “vulnerable”, which is one step below “endangered” but is reserved for species that are still regarded as being at high risk of extinction in the foreseeable future.

The oceanic whitetip is a medium-sized shark that is generally around three metres (9.8 feet) long. It weighs around 170 kilograms (370 pounds). The most distinctive feature of the species is its fins, both dorsal and pectoral, that are rounded and are considerably larger than those of other shark species. The fins and nose have white tips (hence the shark’s name) and the underside is also white.

The oceanic whitetip is found in the tropical and subtropical zones of the Atlantic, Pacific and Indian Oceans. It does not often come close to shore, preferring to stay in the open ocean where it preys on fish such as tuna, barracuda and mackerel, as well as cephalopods (e.g. squid and octopus), turtles and crustaceans. Oceanic whitetips are usually solitary, but groups will gather when a large amount of food is available and they may form feeding frenzies.

Oceanic whitetips can be dangerous to humans under certain circumstances, such as after a disaster at sea. It is believed that up to 600 of the sailors lost when USS Indianapolis was torpedoed in 1945 were killed by oceanic whitetip sharks.

Decline in numbers

Oceanic whitetips have seen a severe decline in numbers in recent years, although the exact rate of decline is not easy to measure given the shark’s migratory behaviour as it follows food sources across large distances of ocean. However, some estimates put the decline at around 70% over the past 50 years.

A major reason for numbers falling has been over-fishing in certain areas, given that the fins of the oceanic whitetip are used to make shark fin soup, which is a highly prized delicacy in parts of Asia. Many have also been lost due to being caught by nets that were set to catch shoals of fish that the sharks were following.

Although the oceanic whitetip has been declared to be a vulnerable species in general terms, it has been classed as critically endangered (the final stage before “extinct” in the IUCN scale) in areas of the central Atlantic Ocean, due almost entirely to losses from “by-catch” in tuna fishing nets. There is therefore considerable pressure on the fishing industry to adopt fishing methods that are less harmful to oceanic whitetips and other shark species.

© John Welford