Trawler capsizes due to jellyfish net

A 10-ton trawler capsized off the coast of Chiba, Japan, when a crew hauled in a net filled with giant Nomura jellyfish. Three sailors were thrown into the water, and the boat overturned, highlighting the dangers posed by these massive marine creatures.

Nomura jellyfish details and spread

Nomura jellyfish, originally from China, can grow up to 2 meters in diameter and weigh as much as 200 kilograms. Their spread is linked to the decline of natural predators and the warming of ocean waters, an issue affecting regions beyond Japan.

Jellyfish overload causes capsizing

The capsizing of the trawler occurred when the combined weight of hundreds of Nomura jellyfish caused the boat to overturn. The net filled with these jellyfish acted as a counterweight, sufficient to capsize the vessel, a problem that has affected Japanese fisheries for years.

Scientific name and migration patterns

The scientific name for the Nomura jellyfish is Nemopilema nomurai, one of the largest jellyfish on Earth. These jellyfish are born off the coast of China and drift through the Japan Sea via the Tsushima Current, with their presence varying by year and sometimes reaching millions in number.

Jellyfish proliferation and environmental factors

In 2009, ideal meteorological and hydrological conditions in their breeding areas led to a demographic explosion of the species. Experts also suggest that the decline of natural predators, such as sea turtles and several fish species, contributes to the increased frequency of these jellyfish.

Jellyfish impact beyond Japan

In August 2025, the Gravelines nuclear power plant in France experienced shutdowns linked to the presence of jellyfish in water intake stations. Similar issues have been reported in the United Kingdom, where the number of jellyfish sightings has increased significantly, linked to ocean warming and a global trend of jellyfish proliferation.