two recent case studies

Keith D.P. Wilson, Stephen Lai Y-h & Thomas D. Dahmer

Hong Kong is dependent on China for potable water supply. Approximately two thirds of Hong Kong's water demand (approx. 940 million cubic metres in 1993/94) is pumped from the East River (Dongjiang), east of Guangzhou. Much of the water is pumped via a series of reservoirs in southern Guangdong to Shenzhen reservoir before transfer to Hong Kong at Muk Wu. From Muk Wu the water can be supplied to eastern, central or western parts of the territory including direct feed into a number of Hong Kong reservoirs. Until recently no evidence existed for fish transfer from the East River catchment to Hong Kong. However, a species, new to Hong Kong, has recently been discovered in Tai Lam Chung Reservoir indicating the possibility of catchment transfer. A second species thought to have been introduced accidentally, has also been recently discovered in a newly established pond at Kau Sai Chai.

Man and Hodgkiss (1981) published the first comprehensive account of the fishes of Hong Kong. The number of species detailed from Hong Kong was considerably expanded in the annotated checklist of Hong Kong stream fishes produced by Chong and Dudgeon (1992). Both of these publications refer to deliberate introductions into Hong Kong by the aquaculture industry but did not discuss or consider the possibility of accidental introductions arising from cross border water catchment transfer or accidental stocking. The dominant freshwater fish in Hong Kong belong to the Cyprinidae family. Chong and Dudgeon recorded 14 genera and 16 species of cyprinid.

Genus Opsariichthys Bleeker, 1863
Opsariichthys bidens Gunther, 1873


Opsariichthys bidens: Günther, 1873:249; Herre, 1932:426, "Hainan"; Lin, 1935:652-653, "Anhui, Chekiang, Fujian, Guangxi, Guangdong (Canton), Hainan, Hebei, Heilongjiang, Hunan, Jiangsu, Jiangxi, Sichuan, Shangdong"; Hoffman, 1937:101, "Hainan"; Tang, 1942:148, "Guizhou"; Pan et al, 1990: 75-77, fig. 33, "Guangdong".

Opsariichthys hainanensis Nichols and Pope, 1927:367; Herre, 1936:630; Tchang, 1937: 103

Opsariichthys uncirostris hainanensis: Nichols, 1943 :97-98.

Opsariichthys uncirostris bidens: Nichols, 1943:97-98.

Material: 1 male, Tai Lam Chung Reservoir, Tai Lam Country Park, Hong Kong, XI. 1994, leg. Stephen Lai.

Biology: Opsariichthys bidens is a moderately small, shoaling, predatory fish, common in mountain streams in Guangdong and Guangxi. The mouth is capable of consuming fish nearly half its body length. It is a highly colourful species with sides of body maculated with prominent vertical, shining dark blue bands separated by light yellowish red bands. The tips of the jaw are brilliant red. The rays of the pectoral, ventral and anal fins are golden green.

It is primarily a small stream species but will readily adapt to reservoir conditions. It is capable of reproducing rapidly in reservoirs. Li & Xu (1995) report that Opsariichthys bidens thrived in Longxi Reservoir following the damming of the Longxi river. It became the dominant predator during the 1950's. However, it was eventually succeeded by Ancherythroculter kurematsui in the early 1960s and in the 1970s by the artificially stocked Erythroculter ilishaeformis. It is considered a pest in Chinese reservoirs as it consumes the fry of commercially stocked carps.

Distribution: China (Anhui, Chekiang, Fujian, Guangxi, Guangdong, Guizhou, Hainan, Hebei, Heilongjiang, Hunan, Jiangsu, Jiangxi, Sichuan and Shangdong) and Korea.

Genus Sinilabeo
Sinilabeo decorus decorus
(Peters, 1880)


Sinilabeo decorus decorus: Pan et al, 1990:169-170, fig. 97, "West River (Xijiang) and North River, Guangdong".

Labeo decorus Peters, 1880: 1031, "Hong Kong,'; Lin, 1933: 337, "Hong Kong; Swatow".

Osteochilus brevis: Lin, 1933:342, "Canton; West River, Guangdong; Kwangsi".

Varicorhinus brevis: Lin, 1931: 108, "Canton".

Material: 1 fish, Kau Sai Chau Pond, IV.1997, leg. T. D. Dahmer.

Remarks: Sinilabeo decorus was originally described from Hong Kong although the specimens did not originate in Hong Kong. They were collected from the West River (Xijiang) in Guangxi and sent to Peters in Hong Kong by Dr. H. Gerlach (see Chong & Dudgeon, 1992:80 and Herre, 1934). In their discussion on Chinese reservoirs Li & XU (1995:22-23) report that Sinilabeo decorus is an economically important fish occurring only in Guangxi reservoirs.

There are more than 350 species of cyprinid known from China. According to Li and XU (1995) the Pearl River (Zhujiang River) catchment, with 167 species, supports the highest number of cyprinids from any of the four major catchments in China. The new record of Opsariichthys bidens is a widely distributed cyprinid species known from all four major river catchments i.e. the Pearl (Zhujiang River), Yangtze (Changjiang River), Yellow River (Huanghe River) and Amur river systems.

The journey from reservoirs in China to Hong Kong would be extremely stressful to sizeable or adult fish. In addition screening would prevent fish of any significant size being abstracted. However, juvenile fish, during their egg and larval stages, might be transferred more easily. No chlorination or treatment of water occurs prior to or during transfer of water to Hong Kong. The occurrence of Opsariichthys bidens in a Hong Kong reservoir does not confirm the introduction of a fish species by catchment transfer. This species may have been deliberately introduced by direct release into the reservoir, although this is unlikely as the fish has no commercial value. It is also possible that the fish has been hitherto undiscovered in Hong Kong since it is common in Guangdong. Nevertheless, there is a distinct possibility that an accidental introduction via river catchment transfer has occurred.

The occurrence of Sinilabeo in a newly established pond at Kau Sai Chau is undoubtedly a result of accidental stocking. The pond at Kau Sai Chau was one of six small ponds and one large reservoir constructed in 1995 to serve the new Kau Sai Chau golf course. The ponds and reservoir provide irrigation water for the greens and fairways, and serve as landscape features and water hazards on the golf course. Stockings of Silver Carp and Bighead Carp were undertaken in 1996. Sinilabeo has, almost certainly, been inadvertently stocked with the introductions of hatchery supplied carps from Guangdong.

Bleeker, 1863. Systema Cyprinoideo rum Revisum. Nederl Tijd Dierk. 1:187-218.
Chong D-h & D. Dudgeon, 1992. Hong Kong Stream Fishes: An Annotated Checklist with Remarks on conservation Status. Memoirs of the Hong Kong Natural History Society, 19:79-112.
Günther, 1873. Report on a collection of fishes from China. Ann. Mag Nat. Hist. (4), 12:239-252.
Herre. A.W., 1932. Fishes from Kwangtung Province and Hainan Island, China. Lingnan Sci. J., 11 (3):423-443.
Herre, A.W., 1943. Description of a new carp from Kwangtung Province. Lingnan Sci. J. 13(2):285-296.
Herre. A.W., 1936. Report on a collection of freshwater fishes from Hainan. Lingnan Sci. J., 15(4):627-631.
Hoffman, W.E., 1937. Distribution notes on some Kwangtung & Kwangsi Fishes. Lingnan Sci. J., 16(1):95- 115.
Li Sifa and Xu Senlin, 1995. Cu/ture and Capture of Fish in Chinese Reservoirs. Int. Dev. Res. Cen., Ottawa. Pub. Southbound, Penang.
Lin, S.Y., 1931. Carp of Kwangtung.
Lin, S.Y., 1933. Contribution to a Study of Cyprinidae of Kwangtung and Adjacent Provinces. Lingnan Sci. J., 12(3):337-348.
Lin, S.Y., 1935. Contribution to a Study of Cyprinidae of Kwangtung and Adjacent Provinces. Lingnan Sci. J., 14(4):651 -663.
Nichols and Pope, 1927. The fishes of Hainan. Bull. Am. Mus. Nat. Hist. 54(2):321-397, 51 figs., 1 pl.
Nichols, J. T., 1943. The Freshwater Fishes of China. Amer. Mus. Nat. Hist. 143 figs, 10 pls., 1 map.
Man S-h and 1.1. Hodgkiss, 1981. Hong Kong Freshwater Fishes. Urban Council of Hong Kong.
Pan, Jiong-hua et al., 1990. The Freshwater Fishes of Guangdong Province . Guangdong Science and Technology Press. pp. 589, figs. 321.
Peters, W.C.H., 1880. Uber eine Sammlung von Fischen, welche Dr. Gerlach ein Hong Kong gesandtehat. Monatsbr. Akad. Wiss. Berlin. pp. 1029-1037.
Tang, D.S., 1942. Fishes of Kweiyang, with Descriptions of Two New Genera and Five New Species. Lingnan Sci. J. 20(2-4):147-166.
Tchang, 1937. The fishes of Hainan. Bull. Fan Meml. Inst. Biol. Zool. , 7:99-110. 


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