Steel cages and an old oil rig installed by China in the Yellow Sea are being called fish farms by Beijing — but South Korea suspects a strategic military build-up in shared waters.

South Korea Condemns the Structures

South Korea’s National Assembly condemned the Chinese platforms on June 23, labeling them “a threat to maritime safety” in a bipartisan resolution. The move followed growing concern over similarities with China’s past behavior in the South China Sea, where initially civilian structures became military outposts.

A new report by the Center for Strategic and International Studies (CSIS) intensified those concerns. “While available information suggests the platforms are focused on aquaculture, concerns that the platforms may be dual-use are not unfounded,” said the report, warning the structures could already be collecting underwater navigation and surveillance data.

Strategic Concerns Deepen

The dispute centers on the Provisional Measures Zone (PMZ), created in 2001 by China and South Korea to manage overlapping Exclusive Economic Zones (EEZ). While the agreement permits fishing, it does not regulate aquaculture, leaving Beijing room to maneuver.

South Korean surveyors attempting on-site investigation were blocked by Chinese coast guard vessels in February, prompting a naval standoff that lasted two hours. Meanwhile, satellite imagery has revealed signs that China may be repurposing additional retired oil rigs as offshore facilities.

“If China uses its structures for military purposes like surveillance and disrupting sea routes, they will eventually threaten our jurisdiction,” warned Chung Min-jeong, an analyst at the National Assembly Research Service.

Beijing’s Dual Strategy: Engagement and Pressure

China insists the installations are deep-sea salmon farms, while urging stronger economic ties with South Korea under President Lee Jae Myung’s new administration. President Lee has pledged both to improve relations with China and reinforce South Korea’s alliance with the United States. He is expected to meet President Xi Jinping at the APEC summit in November.

Despite diplomatic overtures, China’s concurrent naval activities raise tensions. In May, China’s newest aircraft carrier, Fujian, held jet drills in the Yellow Sea, prompting China to declare temporary no-sail zones.

Possible Retaliation from Seoul

Lawmakers in Seoul are now urging counteraction. If China does not dismantle the facilities, they propose South Korea establish its own fish farms in the area and deploy a dedicated survey vessel for expanded maritime surveillance.

“The ambiguity in the 2001 agreement makes it difficult to force China’s hand, but inaction would further erode Seoul’s control,” noted the CSIS report.