Former Philippine president Benigno Aquino has spoken out over the sinking of one of his country’s fishing boats by a Chinese vessel this month in the disputed South China Sea . The captain of the Chinese vessel was “duty bound legally and morally” to stop and offer assistance, Aquino told This Week In Asia , adding that “the very least” the Chinese sailors could have done was stop and check if the other boat’s occupants were OK. Manila lodged a diplomatic protest with China after the Filipino fishing boat was hit on June 9 near Reed Bank, also known as Recto Bank, leaving 22 Philippine fishermen stranded at sea. The fishermen were only rescued thanks to a passing Vietnamese boat, after the Chinese vessel had fled the area. Beijing has vowed to investigate the incident, but Aquino dismissed calls for the Philippines to enter into a joint investigation with China as the two countries do not have “joint sovereignty” over the area of sea in question. A week after the sinking, Philippine President Rodrigo Duterte characterised it as an isolated incident, saying on June 17 that it was “ just a collision, don’t make it worse ”. However, according to US think tank the Centre for Strategic and International Studies’ (CSIS) China Power Project, which tracks China’s rise, 10 ramming incidents involving either the country’s coastguard or its fishing vessels were recorded in the South China Sea between 2014 and 2016. These, in turn, were met with diplomatic protests by the governments of Vietnam, Indonesia , South Korea and the Philippines. Some even led to the deaths of South Korean coastguard officers, according to Lee Ki-beom of the Asan Institute for Policy Studies’ Centre for Public International Law, writing in the journal “Ocean Development and International Law”. Philippines’ Del Rosario back in Manila after Hong Kong deportation As many as five separate ramming incidents involving the Chinese coastguard and Filipino fishermen were reported between 2015 and 2016, often many hundreds of kilometres off the coast of mainland China, according to data from CSIS. In January 2015, three Philippine fishing vessels – the Barbie, Ocean Glory 2 and Ana Marie – were reportedly rammed by Chinese coastguard ships near Scarborough Shoal and had guns pointed at them. China’s foreign ministry countered that the fishing boats were “illegally positioned”. In March 2016, three Chinese coastguard officers rowed over to a Filipino fishing boat near Scarborough Shoal and shooed them away, saying: “This is China coastguard. Go back to Subic.” The Chinese then reportedly left before returning to ram the Filipino boat. The next day, when the Chinese coastguard tried to blind Filipino fishermen with powerful lights and laser devices, the Filipinos countered by waving knives and harpoons, then left. On March 22, 2016, CSIS said there was a “violent exchange” between the Chinese coastguard and Filipino fishermen, with a coastguard ship allegedly ramming one fishing boat. China claimed the fishermen threw firebombs and waved knives and the country’s foreign minister said the fishermen had “defied” orders to leave. On May 25, 2016, a vessel of the bureau of fisheries and aquatic resources was reportedly rammed by Chinese fishermen on board Lady Luck 020 close to Camiguin province in Mindanao. The fishermen were arrested and fined for poaching and their vessel impounded. Under international maritime law, ramming incidents are covered by a little known treaty known as the Convention on the International Regulations for Preventing Collisions at Sea or COLREGS, which entered into force in 1977. China became a party to it in 1980, but the Philippines did not until 2013, a year after a tense stand-off between Philippine and Chinese vessels off Scarborough Shoal. Under the treaty, each signatory country has to draft its own rules on avoiding collisions. ‘China’s not to be trusted’: Rosario wades into boat sinking row Not much is known about China’s rules on the matter, but according to a paper written by Yuelin Zhao, of Dalian Maritime University, Chinese rules on ship collisions do not cover state-owned ships, only privately owned vessels. In his paper, Zhao noted that COLREGS is not intended to assign blame or liability but to determine accountability and “to prevent similar casualties in the future”. The outcome of an investigation by China’s Maritime Safety Administration could then be used in a court of law by any injured party, he wrote.