Evrim Yazgin
Cosmos science journalist
A global study has found that whale sharks will be 15,000 times more likely to collide with ships by the end of the century due to climate change.
The study is published in the journal Nature Climate Change.
Sharks and other large marine animals are increasingly encountering human vessels. While the reasons and impact of collisions between boats and marine life are still being investigated, it is well established that collisions can often lead to injury, permanent damage and death among marine animals.
One animal at risk is the whale shark – the world’s largest fish.
Whale sharks can grow up to 18 metres or more. They are, however, “gentle giants” which feed on some of the smallest sea creatures like krill, crab, fish larvae, small fish and jellyfish.
There is no current estimate for the whale shark population, but their numbers are believed to have halved in the last 75 years according to the Advisory Committee of the 2019 Memorandum of Understanding on the Conservation of Migratory Sharks.
About a quarter of whale sharks are believed to inhabit the waters of the Atlantic, while about 75% are found in the Indo-Pacific.
Researchers of the new study used global climate models and satellite-tracking data of 348 tagged whale sharks from 2005 to 2019. They combined this with shipping traffic models and habitat suitability estimates to predict the risk of interaction between ships and whale sharks over time.
“Whale sharks are highly mobile marine megafauna that can travel hundreds or thousands of kilometres annually,” says co-author Ana Sequeira from the University of Western Australia’s Oceans Institute.
“The species are already vulnerable to collisions with ships due to their use of surface water and the high level of habitat overlap with marine traffic.”
The study found under a high-emissions scenario whale sharks could be forced to move into cooler environments. This would make them thousands of times more likely to collide with ships.
“Moving to cooler regions may protect whale sharks from climate change but we found it can also expose them to risks such as fishing exploitation, increased danger from predators and collisions with ships,” adds Mark Meekan, also from the Oceans Institute.
“This study emphasises the need for quantitative climate-threat predictions in conservation assessments and management of endangered marine megafauna.”
“Forced climate migration could lead to core habitat loss and reduced foraging opportunities for sharks,” says Michele Thums from the Australian Institute of Marine Science. “Unexpected ocean conditions may also lead to increased mortality, and reduced breeding opportunities as where mature adults mate or females give birth is not yet known.”
