A new study from the UK indicates that collisions with large marine vessels are a possible reason for the decline in whale shark populations that has lasted for years.
Marine biologists from the Marine Biological Association and the University of Southampton led the study, which began in 2019 and published earlier this month in the journal Proceedings of the National Academy of Sciences, which tracked the movements of ships and whale sharks around the world.
The researchers said fatal collisions are vastly underestimated and their work shows that more than 90% of whale shark movements overlap with the world’s fleets of cargo, tanker, passenger and fishing vessels.
The team tracked the movements of 348 individual whale sharks, tagged between 2005 and 2019 in the Atlantic, Indian and Pacific oceans, via satellite, and mapped their various “hotspots”.
The researchers submitted the data to the Global Shark Movement Project, which is run by the Marine Biological Association.
“The shipping industry that allows us to source everyday products from around the world could be driving the decline of whale sharks, which are a hugely important species in our oceans,” Freya said. Womersley, PhD student at the University of Southampton. led the study as part of the Global Shark Movement Project, said in a press release.
The International Union for Conservation of Nature’s Red List of Threatened Species lists the whale shark as endangered.
Described as “slow ocean giants”, the researchers said whale sharks can grow up to 20 meters in length and help regulate plankton levels in the ocean by feeding on microscopic zooplankton.
Researchers said whale shark numbers have declined in recent years in many places. However, the reasons are not entirely clear.
Since whale sharks spend a lot of time in surface waters and congregate in coastal regions, experts believed ship strikes could cause “substantial” fatalities.
The study suggests that whale shark tag transmissions ended more often than expected in busy shipping lanes, even after ruling out a technical failure.
Of the 61 tracked beacons that stopped transmitting on busy roads, more than 85% were unrelated to a random technical failure, according to the study.
Researchers suggest this is likely due to whale sharks being struck and killed and sinking to the ocean floor.
“Incredibly, some of the beacons recording depth as well as location showed whale sharks moving through the shipping lanes and then slowly sinking to the seabed hundreds of meters below, which is the ‘gun. smoking “from a fatal collision with a ship”, Prof David said. Sims, founder of the Global Shark Movement Project and senior researcher at the Marine Biological Association and the University of Southampton.
“It is sad to think that many deaths of these incredible animals have occurred around the world due to ships without us even knowing how to take preventative measures.”
The research team said there are currently no international regulations to protect whale sharks from ship strikes, and that this “hidden mortality” could occur with other marine megafauna.
“Collectively, we must devote time and energy to developing strategies to protect this endangered species from commercial shipping now, before it’s too late,” Womersley said, “so that Earth’s largest fish can withstand threats that are expected to intensify in the future. , such as changing ocean climates.”
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