Basking shark sighted off Rijeka: fisherman films the second largest fish in the world – huge, peaceful, fascinating. Biologists give the all-clear.

A rare visitor has turned up in Croatia’s Kvarner Bay: a fisherman from Rijeka filmed a basking shark (Cetorhinus maximus) circling around his boat. The video quickly spread via social media, causing amazement but also some questions.

“Beautiful beast”

As reported by Austrian newspaper Kleine Zeitung, the fisherman is a man who goes by the name “Cali Mero” on social media. He posted the video in the Facebook group “Živi svijet Jadranskog mora” (“Living World of the Adriatic Sea”). In his post, he called the animal a “beautiful beast” – but also added: “I would die of fear if I saw it near me.”

But marine biologists give the all-clear

The basking shark is the second largest fish in the world, after the whale shark, and can grow up to ten meters long and four tons heavy – but it is completely harmless. “It feeds exclusively on plankton and poses no danger to humans,” said Croatian biologist Pero Ugarković in an interview with the Austrian newspaper Kleine Zeitung.

Such sightings are rare, but not extraordinary. Ugarković further explained that basking sharks often go to coastal regions in spring and fall because the plankton density is higher there – especially in calm waters like the Adriatic.

Not the first sighting

As Heute.at added, an approximately eight-meter-long specimen was sighted off Medveja as early as December 2024. Also in March 2024, nature lovers observed a basking shark off Trieste in Italy. The behavior of the animals is typical: they swim with their mouths open near the water surface – sometimes even “basking”, which is why they are occasionally seen from boats or from the shore.

The basking shark lives in temperate marine regions, including the Atlantic, Pacific and Mediterranean. According to marine researchers, it can live to be over 50 years old and sometimes covers enormous distances, despite its leisurely mode of locomotion.