Inner Deep Bay and Shenzhen River catchment area

Country/territory: Hong Kong (China)

IBA criteria met: A1, A4i, A4iii (2004)
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Area: 3,150 ha

Hong Kong Bird Watching Society

Site description (2003 baseline)
Shenzhen River catchment and Inner Deep Bay is an estuarine area comprising a variety of habitats, including freshwater wetland, marine-coastal (intertidal mudflats and mangroves) and man-made (aquaculture fish ponds, tidal shrimp ponds (gei wai) and oyster farms) habitats. The freshwater wetlands are situated at Mai Po and at a flood plain area at the southern side of Shenzhen River namely Long Valley, this is an area of actively managed agricultural land. The mudflats of inner Deep Bay are situated across the Shenzhen River, from Mai Po/Tsim Bei Tsui peninsula of Hong Kong side to Fu Tian of Shenzhen side. A thick belt of coastal mangroves encloses these sites. The inland area consists mainly of farmland, fishponds and tidal shrimp ponds. Surrounding and among these are construction sites, residential area and industrial area. On 4 September 1995, a 1,500 ha of wetlands on the Hong Kong side of the estuary area (Inner Deep Bay) was declared a Ramsar Site, including Mai Po Nature Reserve.Shenzhen River catchement and Inner Deep Bay lies in the northwestern part of the New Territories of Hong Kong. The names of the area includes (1) agricultural lands at Long Valley; (2) fishponds at Ma Tso Lung, Lok Ma Chau, San Tin, Lin Barn Tsuen, Mai Po, Pak Hok Chau, Lut Chau, Tai Sang Wai, Nam Sang Wai, Tin Shui Wai and Tsim Bei Tsui; (3) Mai Po Marshes Nature Reserve; (4) Inner Deep Bay mangroves and inter-tidal mudflat; and (5) mudflat and oyster farm at Sheung Pak Lai

Key biodiversity
A. Other globally threaten species in Inner Deep Bay area:Baikal Teal Anas formosaStable winter visitor, with 1-2 records every year. The high count is 3 birds in 1986 and 1993 (HKBWS 1961-1996).Bear's Pochard Aythya baeriUsually less than 10 were recordedbefore the early 1990s, with a high count of 30 birds on 10 January 1987. However, the number has declined in recent years, with only one or two every year (HKBWS 1972-1997). The recent were high count is of 2 individuals in January 1999 (HKBWS 1999).Relict Gull Larus relictusVagrant with two records involving 3 birds. 31 December 1987 and 1 January 1988 (HKBWS 1988); and 21 November 1992 to 8 March 1993 (HKBWS 1993).B. Other regionally important species in Inner Deep Bay areaChinese Pond Heron Ardeola bacchusDuring the 1990s, the average peak winter period count was 327. This suggests that Deep Bay might hold 1% of the regional east/southeast Asian wintering population, which is estimated to be 25,000 to one million by Rose and Scott (1997) (Carey and Young 1999).Little Egret Egretta garzettaDuring the 1990s, there was an average peak winter count of 1478 in the Deep Bay area. Deep Bay may hold 1% of the regional east/southeast Asian wintering population which is estimated by Rose and Scott (1997) to be 100,000 to one million (Carey and Young 1999). Eurasian Wigeon Anas penelopeWith a five-year mean of peak winter counts of 2420 birds in Deep Bay during the period 1993-94 to 1997-98 (Carey and Young 1999), Deep Bay may hold 0.32% of the regional population, estimated by Miyabayashi and Mundkur (1999) to lie in the range 500,000 to 1,000,000.Northern Pintail Anas acutaThe five-year mean of peak winter counts in Deep Bay during the period 1993-94 to 1997-98 is 6562 (Carey and Young 1999). This is possibly 1% of the Eastern / Southeastern Asia wintering population, estimated by Miyabayashi and Mundkur (1999) to lie between 500,000 to 1,000,000.Common Teal Anas creccaWith a five-year mean of peak winter counts of 4005 birds in Deep Bay during the period 1993-94 to 1997-98 (Carey and Young 1999), Deep Bay may holds 0.4% to 0.8% of the Eastern / Southeastern Asia population, estimated by Miyabayashi and Mundkur (1999) to lie in the range 600,000 to 1,000,000.Eurasian Coot Fulica atraAt a mean peak count for the 1990s of 1620 birds, Deep Bay may hold 1% or more of the regional east/southeast Asian wintering population, estimated by Rose and Scott (1997) to lie between 100,000 and over one million (Carey and Young 1999).Eurasian Curlew Numenius arquataWith five-year mean peak winter count of 800 in the Deep Bay area during the period 1992-93 to 1996-97, the area regularly supports a minimum of 0.8% - 8% of the flyway population, estimated by Rose and Scott (1997) to lie in the range 10-100,000. (Carey and Young 1999).Spotted Redshank Tringa erythropusA conservative estimate of birds utilising the Deep Bay area during a typical year is 3500 birds (Carey and Young 1999). Rose and Scott (1997) estimate that the east/southeast Asian wintering population range is 10-25,000, however, this appears too low and even if the figure is increased by one class to 25-100,000, the area still supports a minimum of 3.5% of the flyway population (Carey and Young 1999).C. Globally threatened species recorded at Sheung Pak NaiSheung Pak Lai is part of the Deep Bay areas lying in the outer part of the bay, and is composed mainly of oyster farms, mudflats and mangrove areas. This is an important feeding area for waterbirds, including the globally threatened Black-faced Spoonbill Platalea minor and the regionally important Great Cormorant Phalacrocorax carbo. 63 individuals were recorded in 29 November 1999 feeding on the mudflat behind oyster farm (Y. T. Yu pers. obs.). This is a regular feeding ground of Black-faced Spoonbill and Great Cormorants, over 2000 Great Cormorant were recorded feeding regularly in January 1999 (Y. T. Yu pers. comm.). Other globally threaten species that have been recorded include Imperial Eagle Aquila heliaca, Red-billed Starling Sturnus sinensis and Black Vulture Aegypius monachus.D. Species recorded in Shenzhen River catchment area:Long Valley is an agricultural area located at the eastern side of the proposed IBA. More than 210 bird species have recorded there since 1993, nearly half the Hong Kong list. Three of the species are "Vulnerable" and eight are "Near-threatened" as listed in Collar (1994). Of the rest, four are regionally important, three have very restricted range in Hong Kong (such as Painted Snipe), three are rapidly declining, and eight have locally significant populations at Long Valley (including several Snipe species).(1)Globally threatened species: Vulnerable: Greater Spotted Eagle Aquila clanga Imperial Eagle Aquila heliaca Japanese Yellow Bunting Emberiza sulphurate Near-threatened: Schrenck's Bittern Ixobrychus eurhythmus Black Vulture Aegypius monachus Grey-headed Lapwing Vanellus cinereus Asiatic Dowitcher Limnodromus semipalmatus Japanese Waxwing Bombycilla japonica Red-billed Starling Sturnus sericeus Chestnut-cheeked Starling Sturnus philippensis(2)Regionally important species with reference to Rose and Scott (1997): Chinese Pond Heron Ardeola bacchus Little Egret Egretta garzetta Common Teal Anas crecca Black-winged Stilt Himantopus himantopus (see also 23-32)E. Other information outside the proposed IBA:Tidal mudflats adjacent to Taipa-Coloane Causeway in Macau: In January 1999 12 Black-faced Spoonbill (Platalea minor) and 1 European Spoonbill were at the tidal marsh area adjacent to the Taipa-Coloane Causeway in Macau (Aston 1999 in litt. To M. Felley). In addition up to 22 Black-faced Spoonbills were present in Macau during the 1996/97 winter period (Christern Bohmer and Paul Aston pers. comm.). It is possible that these involve local movement by Deep Bay birds feeding widely over the Pearl River estuary in response to food availability (Leader 1998). However, a site visit to the area was made on 12 September 1999. It has been totally encircled, with active reclamation undergoing. It is believed that there will be further construction in the area and the site will eventually be destroyed (C. Ma pers. obs.).

Non-bird biodiversity: 1. FishpondsFlora: - Dominant grasses and herbs commonly found on bunds include Alternanthera sessilis, A. philoxeroides, Commelina communis and Ipomoea aquatica. Common grasses such as P. maximum and common weedy species such as Lantana camara, Mikania mirantha and Bidens rubra are commonly occurred.Fauna: - Mammals: Ades (1995) listed 13 mammal species that have been recorded from the fishponds, their banks and bunds at the Mai Po Marshes Nature Reserve. The Javan Mongoose Herpestes javanicus and Leopard Cat Felis bengalensis chinensis have been observed with young, on bunds adjacent to fishponds (Young 1992b). Chinese Otters Lutra lutra chinensis have been seen acrossing tracks between fishponds (Fazey 1993). Seven-banded Civet Viverricula indica scats are also seen regularly on fishpond bunds (Ades unpublished data) and Ryukyu Mouse Mus caroli was first discovered in Hong Kong in 1992 on fishpond bunds adjacent to Mai Po (Chandrasekar-Rao 1995). - Amphibians: Lau (1995) showed that 7 amphibian species have been recorded from the Deep Bay fishponds within the Ramsar site, which is one-third of the amphibian fauna. - Reptiles: Lau (1995) indicated 16 reptile species have been recorded in and around fishponds of the Deep Bay area, which is about 20% of the known reptile fauna native to Hong Kong; this includes the SAR important Chinese Soft-shelled Turtle Pelodiscus sinensis. - Invertebrates: A total of 30 Odonata species out of the 103 known from the SAR have been recorded in fishponds (Townland 1993), and 60% of the identified species belong to the superfamily Libelluloidea (K. Wilson pers. comm.). Among the invertebrate fauna, Diptera and Hemiptera are also important components of the invertebrate fauna, their population densities reaching a the peak in spring and autumn. Dominant benthic invertebrates include Ostracoda and Nematoda. (Aspinwall & Company 1996b)2. Gei Wais (tidal shrimp ponds) and reedbedsFlora: - Local rarities include Ruppia maritima which has been recorded in the gei wai (ERL 1988) and the marine angiosperm Halophylla beccarii is found on the mudflat. - The stands of reed Phragmites communis in Mai Po Nature Reserve are the largest in Hong Kong (46 ha), and one of the largest remaining in Guangdong Province, China (Gao, Y.R. pers. comm). - Mangrove species including Kandelia candel, together with Avicennia marina, Acanthus ilicifolius and Aegiceras corniculatum are well-established in several gei wai.Fauna: - Mammals: In May 1995, a dead Chinese Otter was discovered next to a gei wai at Mai Po Nature Reserve (Cha 1995). Chinese Otter spraints have been found near sluice gates of the gei wai, and the mammal has been seen swimming in the gei wai (Young 1994). Other mammals include Javan Mongoose , Leopard Cat, Seven-banded Civet, Bandicoot Rat Bandicota indica, Japanese Pipistrelle Bat Pipistrellus abramus and Brown Musk Shrew Suncus murinus. - Amphibians: Lau (unpublished data) recorded 5 species of amphibians at the bunds or water edges of gei wais in Deep Bay, including the Chinese Edible Frog Rana rugulosa which is protected in China (Rana tigrina rugulosa) (Romer 1979a; Karsen et. al. 1986) - Reptiles: Lau (unpublished data) also recorded 13 reptile species in and around gei wai in the Deep Bay area, including the Mangrove Water Snake Enhydris bennetti, Oriental Rat Snake Ptyas mucosus, Chinese Cobra Naja naja, King Corba Ophiophagus hannah and Burmese Python Python molurus. Also, there are occasional records of Chinese Soft-shelled Turtle (Lau, unpublished data). - Fish: Lee (1992) recorded a total of 38 fish species from the gei wais in Deep Bay during 1985 to 1989. Dominant fish species include the Tilapias Oreochromis nilotica and O. mossambicus which have the highest density and comprise 90% of the fish community in terms of numbers. - Invertebrates: The endangered Odonate (damselfly), Mortonagrion hirosei, has been recorded in the Mai Po reedbeds. This is a species specific to reedbeds that at present is otherwise known only from Japan (Reels 1994). Nearly 400 species of terrestrial invertebrates are found in the Mai Po reedbeds, with at least 4 species probably being previously undescribed (Reels 1994). - Butterflies and Moths: Mai Po is the type and only known locality for two moth species, Schrankia bilineata (Galsworthy 1997) and Thalassodes maipoensis (Galsworthy 1997). Mai Po also holds a number of moth species which are characteristic of mangrove and reedbed habitats including Chasmina candida, which in Hong Kong has only been recorded at the reserve so far (R. Kendrick, pers. comm. 1999).3. MangroveFlora: - The wetlands around Inner Deep Bay holds some 400 ha of inter-tidal mangroves which is the sixth largest protected area of mangroves in China (Fan 1994). The main species are Kandelia candel, Avicennia marina, Aegiceras corniculatum, Bruguiera conjugata, Exoecaria agallocha and Acanthus ilicifolus Fauna: - Reptile: The Mangrove Water Snake Enhydris bennetti is specially adapted to live in the mangrove. This species has a restricted global distribution and is found only along the coast of southern China between Hainan and Fujian Province (Zhao and Adler 1993). Deep Bay is the stronghold for this species within the territory (Romer 1979b, Lau and Melville 1992), and possibly in the region. The Burmese Python has also been found in mangroves in Deep Bay (A.J.Brandt pers comm.); this indicate this species may uses mangrove as a foraging ground or as a resting place. - Invertebrates: A literature survey of the marine invertebrate community (excluding insects) at Mai Po was made by Lee (1993). A total of 81 species were recorded, while 13 of which are previously undescribed, including the curstacean species Parasesarma Maiponensis. Dominant gastropod snail species include Irvadia bombayana (Peking University 1994). Crustacean species (crab) at the Mai Po Nature Reserve include Uca vocans, U. arcuata and U. acuta. 4. Intertidal MudflatFlora: Hodgkiss and Morton (1978) indicated the only higher plant on the open mudflat is the sea-grass Halophila baccarii which occurs on the seaward edge of the mangroves.Fauna: - Birds: The area regularly support large number of waterfowl in winter (over 68,000 recorded in mid-January 1997) and on migration (up to 20,000 - 30,000 shorebirds). - Mammals: The only known mammals to use the mudflats are Chinese Otter and Crab-eating Mongoose whose scats have been found in the habitat (Young pers. comm.). - Reptile: The only known reptile to inhabit the mudflat within the Ramsar Site is Mangrove Water Snake. - Fish: Mudskippers include Boleophthalmus pectinirostris and Scartelaos viridis dominant on the open mudflat, and the Periophthalmus cantonensis limited to areas near to the mangroves. - Invertebrates:The Shenzhen River Regulation Project EIA carried out by Peking University in 1994 recorded a total of 77 morphospecies, with the most dominant Nereid polychaete worms and bivalves. The polychaete worms biomass recorded is high when compared to other similar studies on mudflats elsewhere in the world. Peking University (1994) showed that their dominance is closely related to organic pollution. These polychaetes and also bivalves provide an important food source for birds.In the past, there were extensive oyster beds on the intertidal mudflat (e.g. at Pak Lai) of the Deep Bay area. Two species of oyster were cultured, namely Crassostrea gigas and C. rivularis (Young and Melville 1993).6. Freshwater MarshesFlora: Dominant species include Phragmites australis, Paspalum distichum and Eleocharis equisetina. There are also records of common sedges such as Cyperus malaccensis var. brevifolius, C. radiata, C. alternifolius and C. polystachyos.Fauna: - Mammals: Local rarities include Chinese Otter which have been recorded only at Mai Po and in the Deep Bay area. - Amphibians: Freshwater marshes are the most important breeding habitat for amphibians such as the local rarity Chinese Edible Frog.

Recommended citation
BirdLife International (2023) Important Bird Area factsheet: Inner Deep Bay and Shenzhen River catchment area. Downloaded from on 30/11/2023.