Category Archives: Scarborough

Scarborough this week: Chinese cutters and fishing vessels

In an effort to highlight the both the value and limits of Vessel Traffic Management Systems (VTMS) to maritime domain awareness, the following thread was created on the DefensePH forum: Who are the people in the neighborhood. The intent for the thread was to post data obtained from various free vessel traffic monitoring Websites that draw information from Automatic Identification System (AIS) services around the world. All screen captures presented in this article come from

This idea is not new. In fact, there was at least one Philippine FB group that focused on collecting AIS data with the end goal of collecting maritime intelligence. While noteworthy, the idea was hobbled by the fact the free AIS data is notoriously unreliable. While freely available AIS can indicate the presence of a ship, the absence of visible ships is not definitive indicator that no ships are actually present — making it ultimately meaningless as in a security context. Furthermore, identity information contained within AIS reports is not tamper proof. According to Windward, a maritime domain awareness company, 1% of all AIS data is actually faked.

Nevertheless, despite its limitations, AIS-data-watching was a potentially fun community activity to which any DefensePH forum member could contribute. So in keeping with the forum’s long-standing goal of promoting roll-up-your-sleeves-and-do-something-patriotism, the thread was rolled out as project on Valentine’s Day, 2017.

Note: For OPSEC purposes, Philippine government vessels are excluded from this thread.

The first activity was to scour major ports for interesting ship-spotting opportunities. Perusal of AIS data in Subic Bay, for example, detected the presence of an outgoing US Navy replenishment vessel that was on the way to East Jahor.

What was not expected, was that Scarborough / Panatag / Bajo Masinloc was actually generating AIS data. Chinese vessels — either deliberately or unintentionally — were announcing their presence in the shoal.

The first vessel detected in the initial inspection was China Coast Guard cutter #3175, a 78-meter member of Shuke II class of cutters.


Exactly how long the vessel had been on station is unclear as the AIS time stamp only refers to the last update event. At that point, the ship had been on station at least 6 hours. It remains in the shoal as of writing.

Not long the initial find, Yu Zheng 312 broadcasted its presence. This 101-meter, 4,590 ton, ship used to be a tanker in the PLA Navy, designated Dongyou 621. It was converted into a fishery patrol vessel and recommissioned in 2013 — becoming the largest member of the fleet at the time.


The photo below shows the vessel on its maiden voyage in its fishery patrol role. Photo c/o China Daily.


The week ended with the detection of three addition vessels in the shoal. AIS data indicated that two were fishing boats designated Qiongsanshay U00313 and Qiongsanshay U00110. No additional validation of this identity was available as of writing.

The third vessel, however, was another coast guard cutter: #3304x. Interestingly, this contact illustrated the imperfection of AIS-based identification as the full number of the vessel was unavailable. It was presumably a member of the Hongming class cutter, a 42-meter vessel.


The presence of these assets in the the shoal demonstrates China’s continued resolve to impose its regulatory controls over the shoal despite their defeat at an UNCLOS tribunal that ruled that their 9-dashed-line claim had no basis in international law.

Chinese patrol vessels within the confines of this shoal came to the forefront of Philippine national consciousness in 2012 when these prevented Filipino fishermen from accessing their traditional fishing ground as part of China’s reinvigorated their efforts to enforce the 9-dashed line claim mentioned above. This resulted in encounters between Philippine and Chinese coast guard ships like the following.

In October 2016, the Duterte administration brokered an agreement with China to allow Philippine fishing boats back to the shoal while side-stepping the matter of exclusive access granted the Philippines by UNCLOS. (See Duterte said he told Chinese: Scarborough is ours). Provided this unfettered access remains, the mere presence of Chinese vessels merely serves as a reminder of PH-CN tensions, and not an indication of another 2012-style escalation.