Oceanic whitetip shark

How the Oceanic whitetip shark has gone from thriving to threatened

For many years sharks, and other marine animals, have been the silent victims of our insatiable greed. A devastating lack of foresight, responsibility and awareness from governments and the general public has left the oceans, once thought to be an inexhaustible source, in a fragile state.

In less than 70 years the Oceanic Whitetip shark (Carcharhinus longimanus) has gone from one of the most abundant pelagic shark in the oceans to threatened with extinction. During its last assessment in 2006 the IUCN (International Union for Conservation of Nature) listed them as Vulnerable globally, but as Critically Endangered in the Northwest and Central Atlantic Ocean. Thirteen years on these ocean wanderers are likely in an even worse state today. Oceanic whitetips are one of the most wide ranging sharks found throughout tropical and subtropical regions (30oN and 35oS) in all oceans. They are suitably named after the habitat in which they live. The Oceanic zone. The Oceanic zone is the area of ocean beyond the continental shelf, where the depth drops to greater than 200m and extends out into the open ocean.

With over 400 million years of evolution behind them, sharks are flawlessly adapted to life in the oceans and their continued presence as top predators and key stone species has helped shape every marine ecosystem. Sharks are one of the oldest extant taxa of vertebrates, having survived 5 mass extinction events.

Oceanic Whitetip 2

Unlike most fish, sharks have a K-selected life history strategy. This means like marine mammals they are long lived, slow growing, late to mature and have few young. These are characteristic of animals that are near the top of the food chain, either due to their size like whales or their success as a top predator like many sharks and orcas. The low threat of predation faced by large sharks removed the need for them to have lots of offspring in order for their species to survive. Unfortunately, it is these K-selected life history straits that have left sharks so vulnerable to rapid over-exploitation by humans. Shark populations have been left defenseless against the relentless onslaught imposed by humans. Sharks cannot be harvested in the same way as teleost (bony) fish are, instead they must be managed more like marine mammals. In response to the rapid depletion of whale stocks from industrial scale whaling the International Whaling Commission (IWC) was set up and signed in 1946. We now need a similar international ban on commercial shark fishing and selling of shark products. But due to an unfortunate lack of understanding and empathy towards sharks from the general public, devising and implementing a successful international ban on commercial shark fishing is proving difficult.

 SO WHAT HAS LED TO THE GLOBAL DECIMATION OF OCEANIC WHITETIP SHARK POPULATIONS?

  1. Their large fins are sort after on the lucrative shark fin market
  2. They live in the top 200m of the open ocean, the same depth that fishing boats target
  3. Average litter size of only 5-6 pups, gestation period of 10-12 months, and (expected) bi-annual mating cycle

The drastic global decline of oceanic whitetip sharks can be attributed to a bad reputation, fishing pressure and the shark fin trade.

Although up to 80% of life on earth lives in the oceans, the open ocean, home to the oceanic whitetip, is biologically a desert. In order to succeed in this environment oceanic whitetips evolved to spend minimal energy looking for food and more time investigating potential food sources that they come across. This is where their iconic fins and behaviour fit in. Their large elongated pectoral fins are perfect for gliding through the water with little effort, which is vital for an animal that may have to travel long distances between meals. Oceanic whitetips are known for being bold, inquisitive sharks often bumping divers. Again this is a reflection of the habitat in which they live. The sheer vastness of their environment means these sharks must thoroughly investigated any potential food. Educating ocean users about sharks would help them better understand their behaviour and respond appropriately to them.

Oceanic Whitetip 3

In the not so distant past when oceanic whitetips populations were healthy and abundant stories from ship wreck survivors often highlighted them as being the main shark present. What really cemented their reputation were stories from survivors of the U.S.S Indianapolis, which was sunk by a Japanese submarine near the end of the Second World War in 1945. Captain Quint provided a disturbing report of the days spent in the sea before being rescued. Although you cannot deny the horrors of the experience, accounts given by other survivors say the hardest part was being thirsty rather than the presence of the sharks. Of the 900 men that made it into the water alive only 317 survived. However, most of the men who didn’t make it died from their injuries, drowning, dehydration, hyperthermia, and saltwater poisoning, not from shark attacks. Umenhoffer, one of the survivors, recalled “you had to be alert when the sharks were around, if they got too close, you’d kick them away”, and another, Lebow said “you could see the sharks swimming around but they didn’t really bother us” (Hodges, 2016). Some men did fall victim to shark attacks, however, inaccurate accounts portraying sharks as mindless killers has led to a lack of empathy from the public and active persecution of sharks.

Since the sinking of the U.S.S. Indianapolis oceanic whitetip shark populations have plummeted. In fact two veterans, James Glancy and Paul de Gelder, wanted to test the shark eating stories from the U.S.S. Indianapolis by spending 43hrs floating in the ocean surrounded by large numbers of oceanic whitetips for a Shark Week program, Sharkwrecked. Unfortunately, over 70 years on it is impossible to find an area of ocean were shark are found anywhere like their former numbers. The most important thing this film highlighted was the lack of oceanic whitetip sharks left. The show was originally meant to be filmed in the North Pacific Ocean where the U.S.S Indianapolissunk, but oceanic whitetips are now so rare there that they had to film in the Bahamas, a successful shark sanctuary and one of the only places you can find relatively large numbers of oceanic whitetips, but still nothing compared to their previous numbers.

Oceanic Whitetip 4

 The shark fin trade

Like other sharks, oceanic whitetips are targeted and killed for their fins to supply the lucrative shark fin trade. Shark fin soup was traditionally only eaten by Chinese nobility and aristocracy, but as the wealth and middle class has grown so has the demand for shark fin soup. The industrialisation of fishing has allowed sharks to be taken from the ocean at an overwhelming rate, and globalisation has created a market for shark fin soup across the world. The popularity of the dish is the single most destructive activity pushing sharks to the edge of extinction.

Thanks to the combined efforts of numerous public awareness campaigns, and government crackdowns on extravagant banquets, reports say the consumption of shark fin soup in China fell by 80% between 2011 and 2018. However, whilst filming for ‘Saving Jaws’ Ocean Ramsey and Juan Oliphant visited China and to their disappointment documented just how prevalent the shark fin market in China remains. Additionally, the demand for shark fin soup remains high in Hong Kong and Taiwan, and is even reported to be increasing in other countries such as Thailand and Indonesia. Unfortunately, the unsustainable demand for shark fins has led to an estimate of 73 million sharks being killed each year for shark fin soup alone.

 Fisheries

Pelagic sharks, including the oceanic whitetip, blue and shortfin mako, are experiencing huge losses as bycatch. Bycatch is a fisheries term used to describe any animal that is caught unintentionally during fishing activity; it may be the wrong species, size, sex or age. Oceanic whitetips are killed in huge numbers by commercial pelagic longline, gillnet and purse seine fisheries (Dulvy et al. 2014).

An increase in fishing pressure throughout their range, inadequate monitoring and vast knowledge gaps in behaviour, biology and ecology, led to a growing concern for the conservation of oceanic whitetips.

Baum and Myers (2004) compared historic longline fisheries data from 1950 and late 1990s to estimate the decline in oceanic whitetip shark abundance in the Gulf of Mexico. Their study reported a decline of 99% over just four generations. Although there is some contention around this figure, similarly dramatic declines have been reported in the Atlantic (Baum et al. 2003) and Pacific Ocean populations (Clarke et al. 2012), with an estimated population decline of >90% in just 15 years (1995-2010) in the Central Pacific (Walsh & Clarke, 2011).

Oceanic whitetip shark populations have suffered such devastating and rapid declines that in 2010 they became the first shark ever to receive protection from the 5 major Tuna Regional Fisheries Management Organisations (RFMOs). They prohibited the retention, landing or storing of the whole or any part of oceanic whitetip sharks by member nations as a measure to boost conservation efforts. In addition, oceanic whitetips were added to CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) Appendix II in 2013, which is an international agreement to control the trade to avoid the collapse of a species.  In 2018, the U.S. federal government listed oceanic whitetips as threatened under the Endangered Species Act, in response to petitions led by the Defenders of Wildlife who stressed the threats the sharks face from overfishing and bycatch in pelagic longline fisheries.

 Oceanic Whitetip 5WHAT DOES THE FUTURE HOLD FOR OCEANIC WHITETIP SHARKS?

Inadequate monitoring, large inaccessible habitat, and illegal, unreported and unregulated fishing have made accurate stock assessments for these sharks extremely difficult. In spite of this, the decline of oceanic whitetips has been brought to people’s attention over the last few years, helping to get them listed on a number of international conventions. However, listing alone is not enough.

Specific national and international maritime laws need to be established and enforced to protect vulnerable shark species. The declaration and enforcement of large open ocean no take zones would significantly aid the recovery of oceanic whitetips, and other pelagic sharks. Although a number of countries have declared their EEZ (exclusive economic zone) shark sanctuaries, little protection is provided for sharks in the open ocean/international waters.

A review of acceptable fishing methods is urgently needed and drastic changes are essential to minimise habitat destruction and significantly reduce the amount of bycatch, which for many fisheries makes up an unacceptable amount of their catch. 

A greater emphasis and effort on educating the general public about sustainable seafood choices is vital. The unsustainable use of ocean resources is as simple as supply and demand. Or more accurately demand and supply. As individuals we are constantly making decisions, and the choices we make regarding seafood are having enormous impacts on the ocean. Reinforcing that when eating seafood you are eating wild animals, and are therefore responsible for making sure you know how it was caught (e.g. tuna longline fishery which have a shocking percentage of shark bycatch) and whether the species and stock it is from are sustainable. If you aren’t sure don’t buy it.

Continued and intensified education and awareness are needed in multiple regions around the world to stop the demand for shark fin soup, which along with fishing is one of the biggest drivers of shark decline. Shark fin soup is no longer acceptable; it is  a luxury seafood item that is driving the major decline of wildlife. It is time for stricter laws, not only on the trade of shark fins which is difficult to monitor and enforce, but also on the selling of shark fin soup itself.

On a more optimistic note given the opportunity, oceanic whitetip sharks have a good chance of recovery. Although our knowledge of their reproduction is still limited most studies have put their age at maturity for both males and females between 5-8 years old (location dependent). So although they only have small litters they have a relatively short generation time compared to other sharks, like bull shark (Carcharhinus leucas) which take over 20 years to reach sexual maturity, and the Greenland shark (Somniosus microcephalus) which could take as long as 150 years.

Although the recovery of shark populations might feel like an issue that is a million miles away and out of your hands, your daily actions can help save sharks.

WHAT CAN YOU DO TO HELP SHARKS:

  • DON’T eat shark fin soup, and avoid eating at places that serve it
  • DON’T eat seafood with high shark bycatch e.g. tuna and swordfish, unless it states it was pole and line caught
  • Know what you’re eating. Shark is often RENAMED, for example in the UK shark might also be called ‘rock salmon’ ‘flake’ or ‘Huss’
  • DON’T buy make up products that contains shark squalene
  • DON’T support big game and sports fishing events that kill sharks
  • DON’T buy shark products e.g. unethical shark teeth (white teeth*), jaws, shark oil or cartilage tablets
  • Share/like only POSITIVE shark stories on social media
  • SUPPORT shark ECO-tourism
  • LEARN more about sharks (for FREE online courses visit our website www.sharklife.co.za)
  • TALK about sharks with friends, family and colleagues to spread awareness
  • Download a SUSTAINABLE SEAFOOD app to help you make responsible choices

*when looking at shark teeth products (usually jewellery) it is important to ask questions about where it is from and look at the colour.  As sharks teeth fall out naturally it is possible to get yellow or black fossil teeth that have been found. If the tooth is white it would have been taken from a shark that was killed. DO NOT buy WHITE TEETH!!!

 

Written by Emma Williams

Photographs by Andy Murch

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