Why are so many sharks dying stranded on California’s beaches?

Nearly 60 per cent of recorded shark strandings occurred in California

More sharks are stranded along the California coastline than anywhere else on the planet, according to a recent study seeking to catalog the beaching incidents.

Strandings happen all over the world, to all manner of sea life. Whale beachings are the most recognisable form of stranding, but other marine animals – including sharks – can suffer strandings as well.

A group of researchers has cataloged stranding data from various sources to take a comprehensive look at what drives sharks onto the beach, and what – if anything – is being done to mitigate it.

The research, published in the journal Fish and Fisheries by a team of scientists from the Federal University of Parana, Brazil, found that shark strandings – which are usually fatal for the animals – primarily affected great white sharks, whale sharks, hammerhead sharks and cat sharks. Leopard sharks were the most impacted by beachings by a significant margin.

Newsweek spoke with the study's co-author, Dr Natascha Wosnick, about why California seemed to be the global centre of shark strandings.

Of the 3,150 shark stranding reports the team examined – data dating back to 1880 – they found that nearly 60 per cent of them occurred in the US.

According to Dr Wosnick, the high number of strandings in the state are caused by a mix of disease and ocean movement off California's coast.

She explained that pathogens in California's waters can kill sharks, leaving their carcasses floating in the water until ocean movement dumps them onto the shore.

In a 2019 mass stranding event, numerous leopard sharks were killed by disease before they washed ashore.

Dr Wosnick told Newsweek that leopard sharks were the species that saw the highest number of strandings. This is likely because the sharks live closest to the shore and often form large schools.

"This could explain why most stranded individuals that are evaluated by pathologists are affected by meningoencephalitis, a disease that can spread very fast within a population," she said.

The research argues that shark strandings are actually far more numerous than current data suggests, and calls for more intense, intentional study of the incidents.

"This phenomenon has been systematically neglected resulting in significant knowledge gaps and decades of poor-quality data," she said. "As a result of such neglect, responses to shark strandings are inefficient with little chance of success in rescue and rehabilitation."

She also recommended that a network of rescue and rehabilitation programs – led by shark specialists – be created to help reduce the number of shark deaths due to stranding incidents.

Dr Wosnick said she hopes that by gathering more data now on shark strandings, future researchers will be able to better protect sharks.