The only waterway on Hong Kong Island to be included in a list of ecologically important streams has been narrowed to the width of a drain by anti-mosquito works carried out by the government.
Boulders from the bed of the stream in Deep Water Bay Valley - home to two species of rare freshwater fish - have been moved to the banks, where vegetation has been cleared by the Food and Environmental Hygiene Department.
Chong Dee-hwa, president of the Ichthyological Society of Hong Kong, said such a complete stream in good condition was hard to find on Hong Kong Island. 'It is really needless [to remove the boulders]. When the stream is altered a little bit, the loss could be immeasurable.'
The stream is one of 33 'ecologically important streams' identified by the Agriculture, Fisheries and Conservation Department.
Yiu Vor, a butterfly researcher who visited the area on Sunday, said about 1.3 kilometres of the channel had been disturbed. 'I saw some department's contractors moving boulders to the bank a few years ago at the lower stream. When I asked, the workers said they were carrying out anti-mosquito work,' he said.
Two workers at a nearby golf course and a hiker who frequented the valley all said they saw government work being carried out in the stream several times a month.
A Food and Environmental Hygiene Department spokesman confirmed it had been regularly carrying out anti-mosquito work in the stream to prevent the anopheles mosquito, which spreads malaria, from breeding. He said the mosquito breeds in unpolluted streams with slow water flow and vegetation on its banks.