River Ecology
As Tung Chung River has not been extensively channelized or filled and has only suffered mild pollution, most of its natural river landscapes have survived. Tributaries and sections at different altitudes connect with its estuary, intertidal zone and mangroves, forming an intact river ecosystem. The Agriculture, Fisheries and Conservation Department has classified this highly ecologically valuable and locally exceptional river as an “Ecologically Important Stream”.
The upland valley at the north of Lantau Peak is home to many native plants, including Exbuchlandia, Magnolia, Manglietia and Illicium plants and has been classified as a “Site of Special Scientific Interest” since 1980. There are many large rocks along the steep upper course and they form complex microhabitats, attracting different fishes, crustaceans and dragonflies. Special amphibians such as the Short-legged Toad (Megophrys brachykolos), the Romer’s Tree Frog (Liuixalus romeri) and the Hong Kong Newt (Paramesotriton hongkongensis) have been found in the river sections close to Tung Chung Road.
As the river is intercepted for feeding Shek Pik Reservoir, the flow is largely reduced with undermined biodiversity along some sections of the middle course of Tung Chung River. Nonetheless, there are a number of fishes living in areas where the flow is still ample. You may find the locally uncommon Philippine Neon Goby (Stiphodon atropurpureus) and the Beijiang Thick-lipped Barb (Acrossocheilus beijiangensis). A variety of dragonflies and damselflies are also frequently spotted, such as the relatively uncommon Hainan Hooktail (Lamelligomphus hainanensis) and Guangdong Hooktail (Melligomphus guangdongensis).
Although part of the lower course has been channelized, some deep pools with slow flow remain and are suitable habitats for fish. Both the Rice Fish (Oryzias curvinotus) and the Paradise Fish (Macropodus opercularis) have been recorded in the freshwater marsh at Fong Yuen. In the nearby fields, one could find many species of dragonflies, such as the Elusive Adjutant (Aethriamanta brevipennis), the Asian Widow (Palpopleura sexmaculata), the Saddlebag Glider (Tramea virginia) and the Lesser Emperor (Anax parthenope). Also, many bird species can be spotted among the fields near this section of the river, including the Red-whiskered Bulbul (Pycnonotus jocosus), the Oriental Magpie-robin (Copsychus saularis) and the Greater Coucal (Centropus sinensis) etc.
The Tung Chung River estuary is a natural estuary, one of the very rare remaining ones in Hong Kong. There are extensive areas of mangroves and mudflat, where numerous coastal organisms feed, nurse their young and seek shelter in the complex microhabitats. The estuary nurtures many species of crab and shellfish, as well as the “living fossil” - the Horseshoe Crabs. The coastal waters are also important for the fishery industry as they provide breeding grounds for many fish species of commercial value. Furthermore, the Mangrove Skimmer (Orthetrum poecilops), a dragonfly listed as vulnerable by the International Union for Conservation of Nature, could be found in the estuary area.