It is common knowledge amongst the Tap Mun fisherman that dolphins and porpoises often frequent the north-eastern waters of Hong Kong. This includes the Hoi Ha and Yan Chau Tong Marine Parks. What is not well known are the species doing this, the reasons why they are there and the frequency of visitation. In June 2016 underwater acoustic recorders were installed in the Hoi Ha Marine Park to gather information about their activity in the bay. These recorders periodically listen for the clicks and whistles these animals emit to navigate and socialise underwater and record them for later analysis. Dolphins spend approximately 8% of their time on the sea surface; the rest of the time is spent underwater. So it is quite difficult to get much information about their range and activity with surface surveys.
This project was carried out by Defend Hoi Ha, the Hoi Ha Action Group and other student led organisations. The preliminary data was used by The Professional Commons in their representation on the Draft Outline Zoning Plan for Pak Sha O before the Town Planning Board on 10 February 2017. It is a part of the long term environmental research being carried out by these groups to show the ecological value and sensitivity in order to try and convince the government to make the enclaves in the Pak Sha O River Valley, including Pak Sha O and Hoi Ha, into a Country Park. Previously these groups discovered the population and range of Chinese Pangolins in the area.
The results of this underwater dolphin study were not as hypothesised. The dolphins are not occasional visitors at all. At least four pods of dolphins regularly visit the area. The largest pod is between five and seven animals; these are bottlenose dolphins. There is a smaller pod of at least three animals, also bottlenose dolphins. There are also one pair of rough tooth dolphins and a fourth group of at least four individual animals, not yet identified.
One further surprise is that a small group of finless porpoises are also regular visitors to the area. Most of the groups detected visit twice a day, in the morning and evening. Regular feeding activity has been detected in the evening period and occasionally in the mornings. The data also suggests that one group ventures in as far as Coral Beach.
The Marine Parks were set up to protect the area and provide for the local marine species, especially those of high ecological value such as these marine mammals. From this data we know the dolphins are feeding regularly in the Hoi Ha Marine Park, and this should be justification for implementing proper protection to this sensitive marine area in order to maximise the amount of fish available for these animals to catch. This includes better controls and regulations restricting commercial fishing in the Marine Parks.
Furthermore, more control and restrictions on sewerage, river pollution and rain run-off entering the bay should also be implemented. This would have been the case, had the Hoi Ha Village enclave been zoned as Country Park when the Outline Zoning Plan was gazetted some years ago. Proper protection in the area would have also prevented the hypoxic event that led to the total demise of the outer coral area of Moon Island and partial die off of the inner coral areas particularly those near the pier area, previously reported in Sai Kung Buzz and other media.
In response to this finding, a few of the local inhabitants have been cooperative in trying to help by becoming conscious of their water usage and thus making an effort to reduce the water pollution entering the bay. Simple measures such as reducing washing machine and dish washer usage will help; placing a brick in the cistern of the toilet reduces the volume of water associated with sewage. These measures not only save money but also minimise the impact on the Marine Park; they are particularly critical to the houses closest to the Marine Park boundary.
The zoning of the Hoi Ha enclave as extended Village, Green Belt, Conservation Area and Coastal protection Area should never have been presented as a serious option for protecting the area from development. What should have happened is the precedent of Tai Long Wan a.k.a. Big Wave Bay where Country Park assignment was proposed as the only possible solution and it was carried out. The entirety of the Pak Sha river valley and associated watershed, and this includes Hoi Ha and Pak Sha O villages need to be a holistic and contiguous part of the Country Park.