Taiwan's coastguard says China is combining maritime militia boats with coastguard and research vessels to expand preparations around Taiwan and the western Pacific.
Officials describe the activity as grey-zone pressure because civilian, scientific and law-enforcement appearances can conceal military support, reconnaissance and coercion.
On August 16, the fishing vessel Minfudingyu 07902 was detected 2.7 nautical miles outside restricted Taiwanese waters alongside Chinese government-linked ships.
Taiwanese units drove it away and placed it on a watchlist, treating the encounter as part of a broader pattern rather than an isolated fishing incident.
Activity has increased since June in overlapping economic zones as Japan and the Philippines discuss their maritime boundary and security cooperation.
Taipei believes the deployments also test routes east of Taiwan that could carry supplies during a blockade or a wider regional crisis.
Beijing says its vessels operate lawfully in Chinese waters, while Taiwan rejects China's sovereignty claims and the military implications of the formations.
Radar, infrared and vessel-identification records are giving Taiwan a more detailed picture of how ostensibly civilian boats could support future operations.
