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Why we need to do more to protect endangered whale sharks

Lethal collisions of whale sharks with large ships are "vastly underestimated."

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Whale sharks, the biggest fish species on Earth, at St Helena Island, South Atlantic Ocean. ( Simon J Pierce via SWNS)

By Stephen Beech via SWNS

Shipping poses an increasingly "significant threat" to the endangered whale shark, warns a new study.

Researchers found that ships are killing large numbers of the biggest of any fish species alive today.

The gentle giants feed on plankton and travel long distances to find enough food to sustain their huge size, and to reproduce. The maximum size of whale sharks is not known but could be as large as 65 feet (20 meters).

Now scientists from the Marine Biological Association (MBA) and the University of Southampton have led ground-breaking research which indicates that lethal collisions of whale sharks with large ships are "vastly underestimated" - and could be the reason why populations are falling.

Whale shark numbers have been declining in recent years in many locations, but it is not entirely clear why.

Because whale sharks spend a large amount of time in surface waters and gather in coastal regions, experts suggested that collisions with ships could be causing substantial whale shark deaths; but there was previously no way of monitoring the threat.

Scientists from 50 international research institutions and universities tracked the movements of both whale sharks and ships around the globe to identify areas of risk and possible collisions.

Satellite-tracked movement data from nearly 350 whale sharks was submitted into the Global Shark Movement Project, led by researchers from the MBA.

The team mapped shark 'hotspots' which overlapped with global fleets of cargo, tanker, passenger, and fishing vessels - the types of large ships capable of striking and killing a whale shark – and found that more than 90 percent of whale shark movements fell under the footprint of shipping activity.

The study also showed that whale shark tag transmissions were ending more often in busy shipping lanes than expected, even when they ruled out technical failures.

The team concluded that loss of transmissions was likely due to whale sharks being struck, killed and sinking to the ocean floor.

Freya Womersley, who led the study as part of the Global Shark Movement Project, said: "The maritime shipping industry that allows us to source a variety of everyday products from all over the world, may be causing the decline of whale sharks, which are a hugely important species in our oceans."

Whale sharks help regulate the ocean’s plankton levels and play an important role in the marine food web and healthy ocean ecosystems.

Professor David Sims said: “Incredibly, some of the tags recording depth, as well as location, showed whale sharks moving into shipping lanes and then sinking slowly to the seafloor hundreds of meters below, which is the ’smoking gun’ of a lethal ship strike."

Prof. Sims, Senior Research Fellow at the MBA and University of Southampton and founder of the Global Shark Movement Project, added: “It is sad to think that many deaths of these incredible animals have occurred globally due to ships without us even knowing to take preventative measures."

There are currently no international regulations to protect whale sharks against ship collisions.

The research team say that the species faces an "uncertain future" if action is not taken soon.

They hope their findings can inform management decisions and protect whale sharks from further population declines in the future.

Miss Womersley, a Ph.D. researcher at the University of Southampton, added: “Collectively we need to put time and energy into developing strategies to protect this endangered species from commercial shipping now, before it is too late, so that the largest fish on Earth can withstand threats that are predicted to intensify in future, such as changing ocean climates.”

The findings were published in the journal PNAS.

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