Introduction of Pui O
Pui O, also called Bui O, is located on the east coast of Lantau Island. There is a rich diversity of habitats in Pui O such as freshwater wetlands, rivers, and mangroves. The residents used to rely on the farming industry, however, the farming industry declined, and many farmlands were left uncultivated in the 70s. With the help of the buffalos, the untended farmlands have become freshwater wetlands.
According to the Approved South Lantau Coast Outline Zoning Plan Np. S/SLC/21, a large area of Pui O is classified as the Coastal Protection Area where landfilling and ground excavation without a permit is forbidden. However, Pui O is still suffering from the filling of mud and construction waste and the Planning Department does not have the power to enforce the law as Pui O is not covered by the Development Permission Area Plan. Buffalos and other animals suffer a great risk of losing their habitat due to fly-tipping activities.
Pui O Habitat
Buffalos eat weed and plough soil on the untended farmlands, gradually turning it into freshwater wetlands. They also step holes in the wetlands which turn into puddles after raining, providing a nurturing ground for many amphibians and insects. The insects, in turn, attract many birds to the wetlands for food.
Chinese Bullfrog (Scientific name: Hoplobatrachus chinensis)
The back of the Chinese bullfrog is olive green with many dark spots. It likes to stay in still water such as freshwater wetlands and marshes, or rivers with slow water current. The edible one that is sold in the market is of the same species as the wild one. However, the population of wild Chinese bullfrog drops drastically due to over-catching. The edible one mostly comes from artificial breeding nowadays. The wild one has a deeper colour, more obvious spots and a sharper response than the bred one. Many religious organisations release bred Chinese bullfrog into the wild which may bring deadly diseases and harm the wild group of Chinese bullfrog.
Asian buffalo & Cattle egret (Scientific name: Bubalus bubalis & Bubulcus ibis)
Asian buffalo is the largest wetland mammal in Hong Kong. Only 130 buffalos are left in Hong Kong, 72 of them are in South Lantau. These buffalos used to be used by farmers to help to farm in the fields and were released after the decline of the farming industry in the 70s. Nowadays, Asian buffalos dig holes in the neglected farmland which helps driving the water flow in the marshes. Moreover, the buffalos are heavy enough to cause mud pit, bringing water to deeper clay layer. Therefore, the water inside the farmlands is not evaporated easily and formed freshwater wetlands. The buffalo ecology of Lantau Island was recognized as the “Humanity Value Landscape Heritage” by the International Council of Monuments and Sites (ICOMOS) in 2014.
Cattle egrets can usually be seen together with Asian buffalos. They follow buffaloes to eat the insects that are scared by buffalos and fly. Buffaloes also benefit from cattle egrets eating their parasite, lowering the risk of illness. Therefore, Asian buffaloes and cattle egrets have a mutually beneficial relationship. One interesting thing about cattle egrets is that they grow orange breeding plumages on their heads, necks and backs during their breed season.
Pui O River passes through the villages in Pui O and flows southward into Pui O Bay. The part opposites to Pui O Lo Wai village is considered as an Ecologically Important Stream by the Agriculture, Fisheries and Conservation Department. The water quality of Pui O River is ideal and with little pollution, therefore, it supports the habitation of many flora and fauna, especially aquatic animals.
Barcheek goby (Scientific name: Rhinogobius giurinus)
Barcheek goby is a very common native fish species in Hong Kong. It can be found in upstream and estuary. Their average body length is 7-8 cm. Barcheek goby is carnivorous, mainly prey on aquatic insects, crustaceans, fishes and fish eggs. It is a benthic fish that often lingers on the stones or sands at the bottom of the stream. Barcheek goby is a migratory fish that they migrate to spawn under stones in estuaries and swim back to live in streams. However, barcheek goby can adapt and reproduce in closed freshwater habitats. There are orange stripes on the operculum of the fish gill.
Sharphead sleeper (Scientific name: Eleotris oxycephala)
The sharphead sleeper is a brackish water fish, it usually lives in estuaries and enters the freshwater region when the tide is low. This species is amphidromous fish. The eggs hatch in downstream and then the newborns migrate to estuaries and inner bays to live as plankton. After the juveniles grow, they will become benthic and migrate back to the freshwater area. Sharphead sleeper has a flattened head and back. Its body has a brownish yellow colour which helps it to hide in the mud of the riverbed. It is currently influenced by estuarine pollution and river engineering.
Introduction of Cheung Sha
Cheung Sha is located on the south bank of Lantau Island. It has the longest beaches in Hong Kong, Upper Cheung Sha Beach and Lower Cheung Sha Beach, therefore, it has the name Cheung Sha (In Chinese, “Cheung” means long and “Sha” means sand). Nowadays, Cheung Sha still preserves its rural condition with few residents.
Cheung Sha Habitat
Upper Cheung Sha Beach is located near the Lower Cheung Sha Beach but they are not continuous with each other. The total length of the two beaches is 3 km. The Upper Cheung Sha Beach is larger than the Lower. Both of them are natural beaches with good water and sand quality, allowing different marine animals to inhabit.
Introduction of Tong Fuk
Tong Fuk is located on the south coast of Lantau Island. There are several streams pass through Tong Fuk, making it suitable for cultivation.
Tong Fuk Habitat
Tong Fuk River is an “Ecologically Important Stream”(EIS) in which many animals are found such as aquatic invertebrates, fishes and dragonflies.
Bee shrimp (Scientific name: Caridina cantonensis)
Caridina cantonensis is a native freshwater shrimp species in Hong Kong. They are small in size and have transparent shells with small dots all over it. They are commonly found in the middle and upper course of the freshwater streams in Hong Kong. They live on stones and dead leaves inside the streams. The eggs of Caridina cantonensis hatch small shrimps directly instead of planktonic larvae. It is because small shrimps can eat algae and organic debris instead of planktonic microorganism, solving the problem of food insufficient in the upper streams. Moreover, small shrimps can grab onto surfaces to avoid being washed away by flash floods, increasing the survival rate of the shrimps.
Target fish (Scientific name: Terapon jarbua)
Target fish is a common species of demersal fishes in Hong Kong. They inhabit in shallow sandy bottoms. The three black stripes on their bodies make concentric circle pattern when seen from above, resembling a target, thus, the name “target fish”. The lowest stripe reaches the middle of the caudal fin. Their dorsal fin has a black blotch. The eggs are guarded by the male. They are omnivorous and feed on fishes, insects, algae, and invertebrates.
Tong Fuk Beach is a popular holiday resort in Lantau Island. From Tong Fuk Beach, one can look at Cha Kwo Chau and Shek Kwu Chau. The sand on this beach is black, probably due to the sand containing dark colour mineral debris.
Introduction of Shui Hau
Shui Hau is located on the south coast of Lantau Island. It has a sheltered bay called Shui Hau Wan and its intertidal area has many different habitats such as freshwater wetland, mangrove and sandflat, supporting lives of more than 180 species. Recently, Shui Hau Wan has been greatly promoted as one of the clam digging hotspots. Clam digging has turned from the livelihood of fishermen to an extremely popular leisure activity. Due to the opening up of remote coastal areas and the power of the internet, large crowds of visitors gather at Shui Hau Wan to dig clams or other bivalves for fun and self-consumption. These human activities have posed adverse effects to the ecology in Shu Hau Wan.
Shui Hau Habitat
Timber storage is a traditional industry in Hong Kong, storing floating timber in the seawater can prevent it from rotting Intertidal mudflat is a kind of wetland located at the boundary between terrestrial and aquatic environments with muddy substratum. They are periodically inundated with seawater at high tide and exposed at low tide. These soft shores are usually found in estuaries and are highly productive habitats. The influx of water from the ocean and river deposit nutritious particles on the mudflat, the surface mud layer is also rich in bacteria and microscopic algae growing in profusion. protect the wood against pests. In the 90s, the contract of the timber storage site in Yam O was terminated due to development of Tung Chung and establishing the new airport. The timber storage industry declined. Nowadays, only a few giant wooden columns for holding the floating timber in the past are left in the shore.
Species in intertidal mudflat of Shui Hau
Asiatic hard clam (Scientific name: Meretrix spp. )
Meretrix is a genus of edible saltwater clams. Different species of Meretrix has different colours and patterns but the shape of their shells are mostly similar to a triangle. Their shells are smooth and shiny. Meretrix spp. are infauna organisms, which are well adapted to burrowing and coping with reduced oxygen concentration. They are filter-feeders. They bury themselves in the mud and protrude their siphon from the mud surface when the tide is high. The suspended particles flow in through the siphon and are filtered by the gills. Meretrix spp. can grow up to 130mm in the past. However, nowadays, Meretrix spp. are becoming fewer and smaller in size due to over-harvesting.
Soldier Crab (Scientific name: Mictyris brevidactylus)
Soldier crabs have collective foraging behaviour. They march in a large group on the mudflat to look for food, resembling army marching, therefore, they are called “soldier crabs”. Soldier crabs are epifauna organisms that live on the surface of the mud, the adult males are often seen foraging on the mud surface at low tide. The juveniles and the females stay in tiny holes in the mudflat and only use their claws to dig the mud for food. Soldier crabs filter the organic matter and algae in the mud. The mud that had been filtered will be piled into a sphere (pseudofaeces) and stacked on the ground.
Intertidal Sand flat
The major habitat in the intertidal zone of Shui Hau is mainly sand flat. It is also the valuable breeding and nursery ground for Chinese horseshoe crabs. Sand flats are habitats composed of coarse and fine sand and the intensity of the wave is in between that of a beach and a mudflat.
Species in intertidal sand flat of Shui Hau
Chinese horseshoe crab (Scientific name: Tachypleus tridentatus)
There are two species of horseshoe crabs in Hong Kong, Chinese horseshoe crabs and mangrove horseshoe crabs. The cross-section of the tail of Chinese horseshoe crabs is more triangular. The horseshoe crab is a keystone species, playing a critical role in maintaining the structure of an ecological community. The blood of horseshoe crabs can make Limulus Amebocyte Lysate (LAL) which is used as a testing agent for intravenous drugs, vaccines, medical devices free of bacterial contamination. Horseshoe crabs are commonly referred as “living fossils”, however, under urban development and human exploitation, the number of horseshoe crabs has been reducing by 90% between 2002 and 2009, further threatening the population of horseshoe crabs in Hong Kong.
Mangroves serve as spawning and feeding grounds for prawns, crabs and fish; and protect coastlines and stabilize marine ecosystems by preventing soil erosion caused by water currents, strong waves and severe weather conditions. Around the globe, there are 60 mangrove species, and among them, eight species can be found in Hong Kong. They are, Acrostichum aureum, Aegiceras corniculatum, Avicennia marina, Bruguiera gymnorrhiza, Excoecaria agallocha, Heritiera Littoralis, Kandelia obovate and Lumnitzera racemosa. In Shui Hau, 6 out of eight species of mangroves in Hong Kong can be found.
Mangroves are highly adapted to the harsh environment on mudflats, facing fluctuating salinity, anoxic conditions and daily tidal variations. Prop roots and buttress roots help mangroves to anchor on the muddy substratum, with pneumatophores and knee-joints that help roots to breathe in anoxic sediments. Salt excretion from salt glands and developing thick cuticle to reduce water evaporation are strategies utilized by some mangroves species to cope with the saline environment.
Species in mangroves of Shui Hau
Splendid fiddler crab (Scientific name: Paraleptuca splendida)
Male has a very large and reddish orange claw for attracting female or fighting other male. The two claws of female are of similar size. The carapace has black and light blue patterns and the walking legs are reddish orange. Splendid fiddler crabs feed on organic materials in mud and hide in burrow when in danger.
Grey mangrove (Scientific name: Avicennia marina)
The grey mangrove is one of the eight species of mangrove plants. It has aerial roots for breathing in high tide. Its leaves have salt glands for excreting extra salts.
Semi-exposed and sheltered shores have a gentler gradient with less wave energy, therefore, boulders accumulate on the shore and form a boulder shore.
Species in boulder shore of Shui Hau
Periwinkles (Scientific name: Echinolittorina radiata)
Periwinkles are common tiny snails found in Hong Kong. They can adapt to an adverse environment. They can secrete mucus to attach themselves to the rock surface and close their operculum to avoid over-heat and desiccation. They are herbivores and mainly feed on algae and lichens. Echinolittorina radiata has a greyish-white shell which is nearly spherical. Its shell has a protruding granular and spiral pattern.
Bubalus bubalis (Asian Water Buffalo), the largest terrestrial mammal on wetlands in Hong Kong can be spotted in Shui Hau. The 72 Asian Water Buffalo living on Lantau Island was entitled “Heritage and Landscape as Human Values” titled ‘HONG KONG BOVIDS AS A SHIFTING SYMBOL OF ‘PROGRESS’: Towards protecting Lantau Island’s environments and cultural heritage’ by the ICOMOS. Buffalo helps the water circulation among deep muddy substratum in wetlands and facilitates the formation of freshwater wetland.