The deep-sea drilling vessel Chikyu sets sail for Minamitorishima.
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Analysis of Automatic Identification System (AIS) data and others have found that China has been conducting sustained maritime survey activities around Japan's exclusive economic zone (EEZ) off Minamitorishima, part of Tokyo's Ogasawara village. The survey area has been concentrated in the southern half outside the EEZ.
From January to February, the Japan Agency for Marine-Earth Science and Technology's deep-sea drilling vessel Chikyu successfully conducted trial excavation of rare earth-rich mud from the seabed within the EEZ around Minamitorishima.
The latest data highlights once again what appears to be a Chinese encirclement of the waters around the island.
According to an analysis by The Sankei Shimbun using Global Fishing Watch (GFW)—a platform that tracks the locations and operating status of vessels equipped with AIS—more than 10 Chinese survey ships in total have been active just outside the EEZ surrounding Minamitorishima.
This activity has continued continuously since 2012, the earliest year for which data is available.
Probing the Perimeter
The UN Convention on the Law of the Sea permits freedom of scientific research on the high seas outside an EEZ.
It appears Chinese companies are planning large-scale mining of manganese nodules—rocks containing rare metals—in waters to the east and south of Japan's EEZ off Minamitorishima.
Most recently, survey activity has centered on those mining blocks. But GFW analysis also found that China had conducted exploration near other sections of the EEZ boundary.
For example, the Chinese survey vessel Xiang Yang Hong 06 traveled in a pattern that appeared to trace the boundary of the EEZ around Minamitorishima.
It repeatedly conducted survey operations while making back-and-forth runs at distances of roughly 150 to 440 kilometers (93 to 273 mi) from the western to the southern edge of the zone.
Another survey vessel, Xiang Yang Hong 03, was observed moving at low speed in a zigzag pattern for several hours in waters just south of the island and outside the EEZ.
Surveying Under Pressure
The Chinese Communist Party's five-year basic policy guidelines for economic management beginning in 2026 call for stronger backing and safeguards for deep-sea and polar exploration. This suggests Beijing is using a variety of methods to probe the seabed.
Meanwhile, military tensions around Minamitorishima have also been rising. In June 2025, four Chinese naval vessels, including the aircraft carrier Liaoning, were confirmed operating in waters near the island's EEZ.
Akira Usui, a specially appointed professor of marine resource geology at Kochi University, said, "There is no legal problem with surveying seabed topography on the high seas."
However, "even at the front lines of marine surveys, countries can feel rising tensions in the international climate," he added. "There have been cases in the past where political conditions were taken into account when conducting scientific maritime surveys."
Xiang Yang Hong 06 has previously been confirmed to have conducted unauthorized maritime surveys within Japan's EEZ near the Senkaku Islands in Okinawa Prefecture's Ishigaki City.
"It's important for Japan to advance scientific research and development in accordance with the rules of international maritime law," Usui said.
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Author: Ryo Nishiyama, The Sankei Shimbun
(Read the article in Japanese)
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