Oceanic Whitetip Shark
Photo: Peter Collings | Deeplens.com
Oceanic whitetip sharks (Carcharhinus longimanus) are named most descriptively due to all of its rounded fin tips being white or showing mottled white patterns. They can grow to nearly 4 meters in length and are one of the most hunted sharks in the world.
Oceanic Whitetip shark anatomy and appearance
The Oceanic Whitetip has a stocky build with a short, bluntly rounded snout, incredibly powerful jaws and fins which are significantly larger than most other shark species. This aggressive but slow moving fish dominates feeding frenzies with its amazing teeth - on the lower jaw they are fang like, relatively small and triangular with a thin serrated tip, however the larger upper teeth are still triangular but broader with edges entirely serrated. It grips its prey with the sharp lower jaw and then uses the strong, upper serrated teeth to saw and slice the flesh. No wonder they are a danger to shipwreck and air crash survivors!
Depending on geographic location the body color may be brown, grey, beige or bronze, sometimes bluish, while the stomach is usually white with an occasional yellow tint. There may also be a dark, saddle shaped marking between the dorsal fins. They have circular eyes and belong to the family group which have nictitating membranes which help shield the eyes when they hunt and eat.
The female is typically larger than the male and young may have black fin tips until they grow to about 1.3 meters, after this, most grow to around 3 meters but the largest ever recorded was 4 meters.
Photo: Peter Collings | Deeplens.com
Habitat and migration of Oceanic Whitetip Sharks
The Oceanic Whitetip is found globally in deep, open water, classed therefore as oceanic pelagic and do not congregate around land masses. They prefer warmer waters between 20 and 28 degrees centigrade, and as such will spend most of their time in the upper layer of the ocean, but are known to swim for extended periods at depths of about 150 meters. Whilst they usually stay at depths above 200 meters, a study in 2013 tagging female Oceanic Whitetips in the Bahamas showed them diving to depths of up to 1000 meters. It is as yet unclear as to why they do this but it is suspected to be a feeding behavior related to hunting squid.
They were once extremely common and widely distributed but numbers have drastically declined over the past years. They can be found from Maine, U.S., south of Argentina in the Western Atlantic Ocean, including the Caribbean and Gulf of Mexico, and from Portugal to the Gulf of Guinea, in the Eastern Atlantic, possibly including the Mediterranean. In the Indo-Pacific, this shark inhabits waters from the Red Sea and East Africa to Hawaii, Samoa, Tahiti and the Tuamoto Islands. In the Eastern pacific the distribution includes waters from southern California, U.S., south of Peru, including the Galapagos. Whilst they are widespread, they are not common and the only place left where regular sightings are possible is the Bahamas.
Diet of Oceanic Whitetip Sharks
The diet of the Oceanic Whitetip primarily consists of bony fishes such as tuna and mackerel, but also includes stingrays, sea turtles, sea birds, squid, crustaceans, dead whales and dolphins and occasionally even rubbish that is disposed in the sea that they mistake for prey species. The species is usually solitary, conservatively cruising near the top of the water column, covering vast distances, searching for food sources. They will occasionally congregate in groups during ‘feeding frenzies’ where food is plentiful, such as around whale carcasses. This seems to be triggered not by blood in the water or by bloodlust, but by the species' highly strung and goal-directed nature. In these situations they direct all their energy and focus on the carcass before returning to their 'energy saving' state when cruising open waters.
Photo: Peter Collings | Deeplens.com
The Oceanic Whitetip is a competitive, opportunistic predator that exploits the resource at hand and is renowned for exploring potential food relentlessly. If other shark species are encountered competing for the same food source, the Oceanic Whitetip usually dominates over them, and may become aggressive. This shark is often accompanied by remoras, dolphin fishes and pilot fishes, and reportedly demonstrates an unusual association with the Shortfin Pilot whale in Hawaiian waters. Although the exact reason for swimming alongside pods of pilot whales is unknown, it is suspected that they are following them to sources of squid, which Pilot whales are extremely efficient at locating.
Oceanic Whitetip shark populations
Reproduction is viviparous, with live young being born after gaining nourishment from a placental yolk-sac that is attached to the uterine wall by umbilical cords. Their gestation period is about 1 year with litter sizes varying from 1 to 15 pups. Sexual maturity is attained at the same age for both sexes, around 6 to 7 years when they reach roughly 2 meters in length. It is suspected that mating season is in early summer in the northwest Atlantic Ocean and southwest Indian Ocean, however there have been many reports of pregnant females outside of the proposed mating season suggesting that their season isn't so strict. Nurseries have not yet been located but very young pups have been found in open waters close to southeastern US.
Conservation of Oceanic Whitetip sharks
The Oceanic Whitetip shark suffers from fishing pressure throughout most of its range, not just from large numbers being caught as by-catch from tuna trawlers and other pelagic fisheries, but also due to it being one of the most actively hunted sharks itself. Due to the shark’s large fins they are one of the most sort after species for finning and are highly prized in international trade. They are often sold to the Far East to make shark-fin soup, with dried lower caudal fin being sold at Hong Kong seafood markets for $265 a pound. However, once the fins have been removed the remainder of the carcass, usually live, is often discarded.
The Oceanic Whitetip shark was assessed in 2019 as 'CRITICALLY ENDANGERED' by the IUCN Red List due to massive declines in reported catch quantities. A study in 2003 showed that numbers were estimated to have dropped by as much as 70% in this area between 1992 and 2000. 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. However, changes in fishing practices and data collection methods complicate estimates. Catches in international waters are often inadequately monitored, and there is simply insufficient data to assess the real impact fisheries are having on the Oceanic Whitetip shark. As this is one of the worlds most widespread shark species, it will take international support and involvement to protect the population from further decline.
As a result of these findings its status on the IUCN Red List was moved from "Lower Risk/Near Threatened" to "Vulnerable" globally and "Critically Endangered". Its move on to CITES Appendix 2, in which their trade must be controlled to prevent possible extinction, is a great step forward for this shark species. Although once thought to be abundant, with many old accounts stating it was one of the most abundant forms of life in the sea, its population is now rapidly declining in our oceans. We hope that increased awareness surrounding this shark and education on the act of finning will help its recovery.
Photo: Peter Collings | Deeplens.com
Oceanic Whitetip sharks and humans
Oceanic Whitetips have a historic reputation as being one of the most dangerous sharks in the ocean, alongside the Great White, Mako, Bull and Tiger shark, however only 5 bites have been recorded since 2009. Famous explorer Jacques Cousteau is quoted to have called these sharks "the most dangerous of all sharks"! The small number of attacks recorded is suspected to be a huge under estimate because of their affinity to open water - with many attacks simply not being reported. Victims from airplane crashes and shipwrecks are historically reported to be among those attacked however accounts from survivors describe many more people dying from salt-water poisoning, exhaustion and drowning than shark attacks. Whilst this may seem all doom and gloom, we are far more of a threat to this species than it is to us - in 2013 a study estimated 100 million sharks are killed each year, many of which are the Oceanic Whitetip. They are vital for a healthy ocean, removing them would cause ecological havoc and the oceans would be a much sadder place without them.
