China’s Most Destructive Boats Return to the South China Sea

May 20, 2019  |  AMTI BRIEF

China’s Most Destructive Boats Return to the South China Sea

After a sharp drop-off in activity from 2016 to late 2018, Chinese clam harvesting fleets have returned to the South China Sea in force over the last six months. These fleets, which typically include dozens of small fishing vessels accompanied by a handful of larger “motherships,” destroy vast swaths of coral reef in order to extract endangered giant clams. The clam shells are transported back to Hainan Province where they fetch thousands of dollars each in a thriving market for jewelry and statuary. Since late 2018, satellite imagery has shown these fleets operating frequently at Scarborough Shoal and throughout the Paracels, including at Bombay Reef.

Biển đFrom 2012 to 2015, Chinese clam harvesters severely damaged or destroyed at least 28 reefs across the South China Sea, as documented by Victor Robert Lee. The typical method employed by these poachers involved anchoring their boats and then dragging the reinforced props of their outboard motors across the reef surface to break up the coral, allowing the clams to be easily lifted out. The ecological results were devastating, and, as a result, in July 2016 the arbitral tribunal that ruled on a case brought against Beijing by Manila found that China had violated its obligations under international law to protect the marine environment. John McManus at the University of Miami, who submitted expert testimony to the tribunal, documented more than 25,000 acres of damage to shallow reef surfaces as a result of Chinese clam extraction as of 2016 (compared to roughly 15,000 acres damaged by dredging and landfill activities to create China’s artificial islands).

Paracel Islands

Sediment plumes created by the activity of clam harvesting boats at Bombay Reef, April 11, 2019.

Now, as then, Chinese authorities are aware of and appear to condone the activities of these fleets. Satellite imagery shows that clam harvesting boats have been operating with regularity at Bombay Reef in the Paracel Islands since late 2018, as evidenced most clearly by the sediment plumes visible in images from April 11. Those plumes, along with the scarring spread across the reef surface, are the telltale signs of the prop-digging method of extraction used during the earlier phase of clam harvesting. And this is occurring despite China’s installation of an “Ocean E-Station” on Bombay Reef last July. The documented surveillance capabilities of this platform suggest that it is relaying information about all activity near the reef to Chinese authorities in the Paracels, yet the clam harvesting continues unabated.

Two motherships towing clam harvesting boats near China’s Ocean E-Station on Bombay Reef, April 11, 2019.

Elsewhere in the Paracel Islands, the damage of recent clam harvesting is visible on Passu Keah. That reef showed no clear damage in imagery collected in February 2018 but by November it was littered with the telltale scars left by the harvesters’ props.

Scarborough Shoal

The clam boats have also returned to Scarborough Shoal, which is a particularly sensitive issue in Sino-Philippine relations. The reef was already extensively damaged by the earlier phase of clam harvesting up to 2016. But imagery from December 2018 reveals the return of a large number of clam boats.

Motherships and clam harvesting boats off the southwest side of Scarborough Shoal, December 7, 2018

A comparison of imagery from December and March also reveals new scarring on the reef from recent extraction.

Scarring and two probably clam boats on the northeast side of Scarborough Shoal, December 7, 2018. The same area with new scarring highlighted, March 8, 2019.

But Scarborough Shoal also offers the first proof of a different method of harvesting clams from deeper reef surfaces where props cannot reach. When a crew from ABS-CBN news in the Philippines traveled to Scarborough in April, they filmed Chinese boats using tubes hooked up to engines on their boats to extract clams in what local fishers said was a very destructive practice that sent sediment drifting throughout nearby waters. This appears to be an adaptation of a tactic employed by salvagers whereby a high-pressure water pump creates enough suction to quickly remove sediment from the seabed. And as at Bombay Reef, it is clear that Chinese authorities are aware of and condoning these environmentally destructive practices. The China Coast Guard maintains a constant presence at Scarborough and was filmed by ABS-CBN visiting the clam harvesting vessels.

ABS-CBN News Channel documents Chinese clam harvesting at Scarborough Shoal, April 2019.

The ABS-CBN crew was also able to film large piles of extracted clams tagged and deposited across the reef for later collection by the Chinese poachers. Satellite imagery from March appears to show these piles, visible as irregular white spots scattered around the reef, which were not present in previous images.

Suspected clam shell piles and a Chinese boat along the southwest side of Scarborough Shoal, March 8, 2019.

Spratly Islands

AMTI has not found clear evidence of new clam harvesting in the Spratly Islands. But on April 7, during the same period that Chinese maritime militia vessels were clustering around Philippine-occupied Loaita Island and Loita Cay, a mothership and a number of small boats were present at nearby Lankiam Cay. The mothership was about 20 meters long while those seen at Bombay Reef are typically closer to 30 meters, but the smaller boats are roughly the same dimensions.

A mothership towing smaller boats at Lankiam Cay, April 7, 2019. A small boat at Lankiam Cay, April 7, 2019.

The absence of new scarring on Lankiam Cay after this boat’s departure would have previously indicated that no clam harvesting had taken place. But the new methods being used to extract clams at Scarborough Shoal suggest that documenting the activities of these Chinese fleets has become more difficult. Unlike the prop scarring on shallow reef surfaces, destruction caused by high-pressure water pumps used in deeper waters is unlikely to be visible in satellite imagery. That suggests that for every clam harvesting operation that is documented in the South China Sea, others will go unnoticed. But with tens of thousands of acres of reef surface already damaged or destroyed and fish stocks teetering on the brink of collapse, the effects of this wanton destruction of the marine environment will be felt across the region.

Recent Analysis

Balikatan 2019 and the Crisis in Philippine-China Rapprochement by Renato Cruz de Castro

Duterte’s Scarborough Shoal Moment by Richard Heydarian


The Center for Strategic and International Studies (CSIS) is a bipartisan, nonprofit organization founded in 1962 and headquartered in Washington, D.C. It seeks to advance global security and prosperity by providing strategic insights and policy solutions to decisionmakers.

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