China tightens grip on Panatag shoal

(UPDATE) CHINA has tightened its grip over Panatag Shoal or Bajo de Masinloc, also known as Scarborough Shoal, in the past year, doubling maritime patrols and expanding an exclusion zone that keeps Philippine government vessels at least 25 nautical miles away from the disputed feature, according to new tracking data released by Stanford University’s SeaLight program.

Satellite imagery and automatic identification system (AIS) data from May 2023 to April 2025 showed a sharp rise in Chinese activity around the shoal.

SeaLight said 78 China Coast Guard (CCG) and maritime militia vessels transmitted more than 1.57 million AIS signals during the period — more than double the 724,000 signals from 57 ships the previous year.

The data also revealed a widening of the area covered by Chinese patrols, with activity building up toward the east, closer to the Philippine mainland.

“These moves show China’s intention to establish a de facto blockade,” said Ray Powell, director of the SeaLight program and a former US Air Force officer. “It is using sustained maritime pressure to create new facts on the ground.”

The Philippines, while unable to match China’s scale, has tried to maintain its presence.

Philippine Coast Guard (PCG) and Bureau of Fisheries and Aquatic Resources (BFAR) vessels recorded 217,000 AIS signals from May 2024 to April 2025 — nearly four times more than the 55,000 signals generated by seven ships the year prior.

Still, Philippine vessels have been unable to breach China’s expanding maritime cordon around the shoal since early 2024.

Data compiled by SeaLight researcher Anna van Amerongen showed a troubling picture of intensifying Chinese dominance.

Ship positions recorded on the first day of each month showed not just expanded patrol zones but increasingly aggressive Chinese behavior, including dangerous maneuvers against Philippine vessels and aircraft operating in the area.

In parallel with its maritime buildup, Beijing has moved to solidify its claims through legal means, recently introducing new baselines in the South China Sea.

Analysts see this as part of a broader strategy of “incremental encroachment” aimed at normalizing China’s control over disputed areas, particularly Scarborough Shoal, which it seized from the Philippines in 2012.

Despite being located well within the Philippines’ 200-nautical mile exclusive economic zone (EEZ), as recognized under the 1982 United Nations Convention on the Law of the Sea (Unclos), Philippine access to the shoal has been almost entirely blocked.

A 2016 ruling by the Permanent Court of Arbitration in The Hague invalidated China’s claim, declaring it had “no legal basis.” Beijing has refused to accept the ruling.

Manila continues to assert its sovereignty through limited patrols and diplomatic engagement, but the imbalance at sea remains stark.

“The Philippines is pushing back with what it can,” Powell said. “But it is clearly facing a long, uphill battle.”

Tensions rose again last June 20 when the Philippines accused Chinese vessels of dangerous and unprovoked action during a supply run to local fishermen near the shoal.

The PCG reported that four BFAR vessels encountered six China Coast Guard ships, two People’s Liberation Army Navy warships, and several maritime militia boats.

At 10 a.m., the BRP Datu Taradapit was hit by a water cannon fired by CCG-4203 about 15.6 nautical miles southwest of Bajo de Masinloc, after the Chinese vessel approached within 600 yards.

The Daty Taradpit veered off to avoid further damage. Half an hour later, another CCG vessel, CCG-3105, fired a water cannon at BRP Datu Tamblot 18.1 nautical miles southeast of the shoal, but the attempt missed.

Despite the provocations, BFAR was able to deliver fuel subsidies to more than 20 local fishing boats, the PCG said.

Panatag Shoal is a triangular coral reef ring surrounding a lagoon, rich in marine life and long relied on by Filipino fishermen.

The shoal is 124 nautical miles west of Masinloc town in Zambales.