Sixteen white dolphins have been found dead in the Pearl River estuary this year, the highest toll recorded. A Hong Kong conservation expert said it was likely that the figure was underreported and called for more efforts to combat pollution. The number of dead dolphins spotted from January to July this year is the highest since counting began in 2003. Eight of the dolphins were found in the river, three off Macau and five off Hong Kong. Chen Xi, deputy technology chief of the Pearl River Estuary Chinese White Dolphin National Nature Reserve, said preliminary observations suggested many dolphins were trapped in shark nets along the coastline. He also intimated that pollution may have played a part, though he refused to say pollution directly caused the deaths. 'Some dolphins' intestines were found filled with parasites. We also found some dead dolphins to be thinner than others,' said Mr Chen. He said there was still no conclusive evidence on cause of death, but added his organisation would step up patrols to fight illegal fishing in the reserve zone. Mainland media said the high death toll was due to busy maritime traffic and noise from construction projects. One newspaper even attributed the increase in deaths to 'significantly more typhoons this year'. Samuel Hung Ka-yiu, chairman of Hong Kong Dolphin Conservation Society, said the death toll in the Pearl River estuary was probably underreported. Dr Hung put the total number of white dolphins in the area at about 1,500, of which about 200 live in Hong Kong waters. He said about 10 to 12 dead dolphins had been found in Hong Kong every year over the past decade. 'So finding 15 to 16 in the entire region in the first six months is really not that many. There is no meaning behind this figure,' said Dr Hung. Guangdong environmental figures show that 1.57 billion tonnes of industrial waste was dumped into the Pearl River in 2003. This increased to more than 2.1 tonnes last year. While pollution might not be the immediate cause of death, Dr Hung said pollution would weaken the dolphins' immune system. Dr Hung urged mainland officials to come up with effective measures to reduce pollution and regulate illegal fishing in the dolphins' habitat. 'These are the urgent issues that they have to deal with, instead of blaming it on more typhoons,' Dr Hung said.