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Introduction of Exotic Aquatic Species in Singapore L.M. CHOU T.J. LAM Department of Zoology National University of Singapore Kent Ridge, Singapore 0511 Chou, L.M. and T.J. Lam. 1989. Introduction of exotic aquatic species in Singapore, p. 91-97. In S.S. De Silva (ed.) Exotic Aquatic Organisms in Asia. Proceedings of the Workshop on Introduction of Exotic Aquatic Organisms in Asia. Asian Fish. Soc. Spec. Pub!. 3, l54p. Asian Fisheries Society, Manila, Philippines. Urbanization has changed much of Singapore's landscape and affected its natural fauna. Exotic species have been introduced for economic or commercial purposes. Two such species that have become firmly established in Singapore's inland waterways are the guppy (Poecilia reticulata) and the tilapia (Oreochromis mossambicus). The country lacks extensive natural inland water bodies as well as indigenous inland fisheries, and the introduction of exotic species is not likely to cause much concern. No serious study on the ecological impact of introduced species has been made. The natural landscape of Singapore has changed drastically since the island's founding in 1819. During the early days, large tracts of forests were cleared by industrious cultivators and replaced by plantations of pepper, coffee, rubber, sugar-cane, gambier and other crops. As urbanization continued, remaining forests as well as disused and existing agricultural land were systematically cleared at increasing pace for commerce, industry and housing. Today, 28.6 km2 of nature reserves and secondary forests surrounding the reservoir catchment areas remain while land for agrotechnological use such as for agriculture and aquaculture, has been designated in ten parks intended for farming at high technology level. These parks occupy about 180 hectares, and the area is expected to increase to 2000 hectares over the next decade (Yap 1987). The drastic changes in the environment affected the natural fauna of the island. Some species of plants and animals were reduced or even exterminated. At the same time these changes favoured the proliferation of other species that were introduced accidentally or intentionally. Some of the exotic species were brought in and raised for their ornamental, economic or commercial potential. This included indigenous ones which would otherwise have been exterminated had they not been introduced for the reasons mentioned. This paper will deal only with the aquatic animal species. No studies have been made on the ecological significance and implications of introduced species. Aspects such as parasite and other disease introduction and transmission, their effect on the environment, and the competition of introduced species with indigenous ones have not been given attention, but warrant systematic investigation. In cases where the ecological impact of an introduced species can be predicted legislative and other measures have been taken by the government to stop their entry. An example of this is the ban on the import of piranhas under the 91
92 Fisheries (Piranhas) Rules 1971, enacted as a supplement to the Fisheries Act, 1966. It is now illegal to rear or release the fish into natural waterways. Species Introduced for Biological Control The only species recorded as having been introduced for biological control is the guppy, Poecilia reticulata. This species was introduced in 1937 for mosquito control (Herre 1940) and has since become well established in polluted waters having free ammonia concenirations of a few hundred parts per million (Johnson 1973). Freshwater Species Trionyx sinensis (Chinese soft-shell terrapin) Species Introduced for Culture In the early 1970's, some hatchlings were brought in from Taiwan by an enterprising farmer to test the viability of the species in Singapore. It adapted well to the tropical conditions. Because of its higher fecundity and faster growth rate under these conditions, it is now cultured in preference to the slower-growing native species, T. cartilagineus. Endemic to China, T. sinensis has been successfully cultured for over 60 years in Japan and 100 years in Taiwan. The warm climate in Singapore allows a higher production rate than in the temperate region, but its culture is land intensive. Therefore, although Chinese soft-shell terrapin farming is lucrative in Singapore, it is limited to two farms. There have been cases of escape of these terrapins into inland water systems. Although the implications have not been considered, there is every likelihood of some ecological disturbance because of their ability to reproduce faster in the tropics, and their voraciousness (live fish forming the main part of their diet), especially if they find their way into sheltered waters where fish are stocked, such as reservoirs. Crocodilus porosus (estuarine crocodile) and Tomistoma schiegeli (Malayan gavial) Sharma (1973) reported that it was unlikely for any large individuals of Crocodylusporosus to be found in the wild although they were a major hazard in coastal waters and mangroves in the earlier days. The presence of the Malayan gavial in Singapore waters although rumoured, has never been substantiated. Both species have together with other crocodilian species, been reintroduced for farming. Their escape always causes great concern because of the apparent danger to man and occasional escapes have occurred.
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Exotic Aquatic Organisms in Asia /
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Exotic Aquatic Organisms in Asia Pr
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The Introduction of Exotic Aquatic
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Introduction This special publicati
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help to promote national awareness
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Conditions in Europe and North Amer
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2 taken as the basis for the introd
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4 with respect to other introductio
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6 Costa-Pierce, B. 1988. Study miss
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8 extinction of the endemic rainbow
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10 bottom substrates by European ca
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12 Arthington 1988; Lloyd 1987); G.
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14 Apparent Extinction of the Lake
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16 successful and more often than n
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18 Reznick, D. 1981. 'Grandfather E
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20 -24° 4' 4 - I- .300 Cl) '1 S 36
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22 The terminology associated with
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24 Table 2. Translocations of indig
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26 MELANOTAENIIDAE Melanotaenia spl
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28 ELEOTRIDAE - GUDGEONS Hypseleotr
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30 POECILIIDAE - LIVEBEARERS Gambus
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32 References Allen, G.R. 1982. A F
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34 Robinson, S.E. 1982. The ecology
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36 1973. It has been cultured in so
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38 northern Japan, settled off Dali
Page 51 and 52: 40 Table 1. The exotic aquatic food
Page 53 and 54: 42 Table 2. The preliminary list of
Page 56 and 57: Impact of Exotic Aquatic Species in
Page 58 and 59: Table 1. Salinonids introduced into
Page 60 and 61: Grass carp The grass carp, Ctenopha
Page 62 and 63: Table 4. Total catch and tilapia yi
Page 64 and 65: Salvinia molesta, a floating fern o
Page 66: Joy, PJ., K.R. Sathesan and D. Jose
Page 69 and 70: 58 Table 1. Introduced aquatic spec
Page 71 and 72: 60 The 1940s The Inland Fisheries D
Page 73 and 74: 62 Indonesia includes three differe
Page 75 and 76: 64 information on the status of fau
Page 77 and 78: 66 Table 1. List of exotic aquatic
Page 79 and 80: 68 Table 1. Continued Taxonomic Sta
Page 81 and 82: 70 From this historical review, it
Page 83 and 84: 72 what they perceived as economica
Page 85 and 86: 74 Table 1. Fate of the introduced
Page 87 and 88: 76 While it is likely that at the o
Page 89 and 90: 78 Pearl Spot The pearl spot, Etrop
Page 91 and 92: 80 Trengganu Enactment No. 8 of 196
Page 93 and 94: 82 References Annual Fisheries Stat
Page 95 and 96: 84 long time ago as shown by the fa
Page 97 and 98: 86 Discussion and Recommendations E
Page 99 and 100: Table 1. Exotic aquatic species int
Page 101: Table 1. Continued Diseases/Parasit
Page 105 and 106: 94 (Caranx ignobilis) golden treval
Page 107 and 108: 96 Table 1. Main species of aquariu
Page 110 and 111: Status of Introduced Species in Sri
Page 112 and 113: Exotic Aquatic Species in Taiwan I-
Page 114 and 115: appreciated in the context of the w
Page 116 and 117: However, A. anguilla cannot tolerat
Page 118 and 119: Today, most of these carps are poly
Page 120 and 121: Caiman latirostris and Alligator mi
Page 122 and 123: Conclusions The case of the tilapia
Page 124 and 125: Table 1. Continued Culture Status P
Page 126 and 127: Table 2. Record of tilapia introduc
Page 128 and 129: Annex I. Continued Dascyllus melamu
Page 130 and 131: Exotic Aquatic Species in Thailand
Page 132 and 133: Present Status of the Exotic Specie
Page 134 and 135: Table 1 a. Exotic fishes introduced
Page 136 and 137: Australian Government Position: Int
Page 138 and 139: There are presently eight State or
Page 140 and 141: egulate any activity likely to have
Page 142 and 143: Appendix II. Continued Name State o
Page 144 and 145: Recommendations of the Workshop 1.0
Page 146 and 147: (two more to be co-opted) was appoi
Page 148 and 149: Mr. J. Maclean, do ICLARM, MC P0 Bo
Page 150 and 151: Appendix I Definitions of Exotics T
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Appendix II Assessment of the Impac
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Table All.3. Assessment of the stat
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Table All.6. Assessment table of th
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Table All.8. Assessment table of th
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Table All.10. Continued Family/Spec
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Table Affi. Indigenous species whic
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Appendix V Existing Legislation or
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TITLES IN THE ASIAN FISHERIES SOCIE
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