and Ouk Vibol
|There is currently no well documented evidence of exotic species causing environmental harm in Cambodia|
Cambodia is fortunate to have some of the most productive freshwater fisheries in the world. The Mekong, Tonle Sap and Bassac rivers, their tributaries, a number of lakes, and a vast area of floodplain are rich in aquatic resources which support these inland fisheries. An estimated 500 freshwater fish species (Rainboth, 1996) occupy various ecological niches, including plankton feeders, detritus feeders, piscivores, and omnivores. The Great Lake on the Tonle Sap is the largest lake in Southeast Asia, and supports inland fish production that provides food security and income generation for millions of people living in the country. Fish is the main source of protein for Cambodian people, with an estimated average per capita consumption of 30 to 40 kg/person/year. Recent estimates of Cambodia's freshwater capture fisheries indicate annual catches of 400000 tons per year, having an annual retail value between US$ 250–300 million.
Increasing urbanization, industry expansion, and rapid population growth result in the alteration of natural ecosystems. These factors, coupled with conflicts in water management, overfishing, and illegal fishing activities are all contributing to observed declines in wild fish production from inland waters. Human interference with aquatic ecosystems impacts natural aquatic habitat and the biodiversity of aquatic flora and fauna. This includes freshwater fishes supporting commercial fisheries that are threatened, and several indigenous fish species that are either endangered or extinct in Cambodia.
As capture fisheries decline, aquaculture can play an important role by augmenting fish production to provide sustainable food resources for Cambodians. Aquaculture producers use seed from indigenous fish collected from the wild, and several exotic fish species that have been introduced to Cambodia. The use of alien species in aquaculture is believed to increase fish production and improve the livelihood of rural populations. However, alien species can be a significant threat to aquatic biodiversity, and they have the potential to disrupt local aquatic ecosystems.
This paper highlights the present status of introduced fish species, problems faced in fisheries and aquaculture, and mechanisms for the control and responsible use of alien fish species in aquatic ecosystems.
Status of aquaculture
Inland aquaculture is conducted using cages, fenced pens and open ponds. The utilization of cages and pens for aquaculture production is a practice thought to have originated in Cambodia. Aquaculture production, especially inland pond and cage culture, has increased from 2000 metric tons in 1984 to 20000 metric tons in 2002. With this as a model, it is likely that Cambodia will continue to experience similar rapid expansion in the industry.
Cage aquaculture is the most common production system and is responsible for about 80% of total inland fish production. These systems use primarily indigenous fish species collected from the wild. Two major species found in cage culture are the catfish, Pangasianodon hypopthalmus and Channa micropeltes, the red or giant snakehead. Other species are also cultured such as Pangasius bocourti, Barbonymus gonionotus, Leptobarbus hoevenii, Ostiochilus melanopleurus, and others. Some exotic fish are also cultured in cages, primarily Oreochromus niloticus and other tilapia species.
Pond culture of fish is the least developed technique in Cambodia. It contributes approximately 1000 tons per year, or slightly less than 20% of total freshwater aquaculture production. The use of intensive culture systems is concentrated in areas around Phnom Penh and Kandal Province, while small-scale systems are in more wide spread use. The major indigenous fish species cultured intensively are Pangasianodon hypophthalmus and hybrid catfish. Some exotic species such as: Clarias gariepinus and Hypophthalmychthys molitrix are also cultured intensively. The Department of Fisheries, with the assistance of a variety of development organizations has actively promoted small-scale aquaculture in the upland areas for food security. Most of this production occurs in impoundments behind small dams, some of which are linked to rice paddies. This aquaculture is predominantly based on introduced species of fish and their escape may present a serious threat to local biodiversity. There are at least 15 alien species that have been introduced in Cambodia since 1970, including four Chinese major carps: silver carp (Hypophtalmychtys molitrix); bighead carp (Aristichthys nobilis); Grass carp (Ctenopharyngodon idella) and common carp (Cyprinus carpio), three Indian major carps: Rohu (Labeo rohita); Mrigal (Cirrhinus mrigala) and Catla (Catla catla), Java tilapia (Oreochromis mossambicus), Nile tilapia (Oreochromis niloticus), red tilapia (O.niloticus x O. mossambicus), African catfish (Clarias gariepinus), and the Giant gourami (Osphronemus gouramy). Most alien species can adapt well and grow very fast in pond environments.
Coastal aquaculture in Cambodia was negligible before 1988 (Nam, 1999), but is now developing along the coastal zone in three provinces, Koh Kong, Sihanouk Ville and Kampot. Penaeus monodon shrimp seed collected from the wild or imported from Thailand and Viet Nam are commonly cultured in ponds. Shrimp farming peaked between 1994–1996 with production of 600–750 tons, after which it declined drastically amounting to only 50 tons in 2002. Seaweed (cottony II) was introduced to Cambodia in 1999 from Malaysia for coastal farming.
Introduction of alien/exotic fish
Alien species, also called exotic or non-indigenous species, are species that are not native to a specific locality or ecosystem, although they may be found elsewhere in the same country or beyond the country's borders. They represent all phyla, from microorganisms to various plants and animals, and are both terrestrial and aquatic.
Introduction of exotic fish species into Cambodia has occurred for decades. Fish have been introduced intentionally or by accident for various uses including commercial production and recreational purposes.
Although Cambodia has rich indigenous fisheries resources, many different varieties of alien fish species have been introduced for farming since 1969 to supplement the demand for fish seed from wild. The most common introduced species in Cambodia include carps, tilapia and a number of other African species. These species are desirable because they are readily reproduced in captivity, exhibit fast growth and adapt well to pond systems. Environmental concerns arise when these alien species escape the confines of the pond and spread into natural aquatic ecosystems where they compete with native species.
Some fish are intentionally released into the wild in closed reservoirs and canals to enhance the natural stocks and increase fish populations. A number of fish species were released intentionally to control aquatic weeds, while others were introduced for ornamental purposes and were subsequently intentionally or accidentally into natural water bodies.
Under heavy rainstorms or seasonal flooding, fish may escape from farms that are not properly fenced or poorly sited. Introduced plants may harbor eggs of other species that are inadvertently introduced along with them. In some cases, exotic species are knowingly introduced into native waters by private business creating the possibility that they will out compete the natives.
|The decline of endemic fishes is most often reported in association with disturbed and polluted habitats|
Status of alien species in the natural ecosystem
Information on exotic fish from migration studies
Since 1997, the Fisheries Program of the Mekong River Commission (MRC) has been assessing local knowledge in the Lower Mekong River Basin. The objective of the study is to provide information on the life cycles of important Mekong River fish species including the location and seasonality of migration and spawning. Databases resulting from these studies include records of exotic fish species, including many Hypophthalmichthys molitrix, Labeo rohita, Cyprinus carpio, Oreochromis niloticus and Oreochromis sp. These species have been widely recognized and recorded by local fisherman along the Mekong and it's tributaries.
The MRC surveys in the Mekong mainstream included 12670 records documenting a total of 191 species. In Mekong tributaries 6616 records documented 173 species. A detailed listing of the species recorded is found in Table 2.
Table 1. Information on alien species introduced in Cambodia for aquaculture
|Common name||Species||Source||Year||Aquaculture Use||Established in the wild||Ecological impact||Socio-economic impact|
|Silver carp||Hypophtalmychtys molitrix||Taiwan Viet Nam||1969 1981||Widely||Few||Unknown||Beneficial|
|Bighead carp||Aristichthys nobilis||Viet Nam||1981||Widely||Few||Unknown||Beneficial|
|Grass carp||Ctenopharyngodon idella||Viet Nam||1981||Widely||Unknown||Unknown||Beneficial|
|Common carp||Cyprinus carpio||Taiwan Viet Nam||1969 1981||Widely||Few||Unknown||Beneficial|
|Rohu||Labeo rohita||Viet Nam||1986||Widely||Few||Unknown||Beneficial|
|Mrigal||Cirrhinus mrigala||Viet Nam||1980||Widely||Unknown||Unknown||Beneficial|
|Catla||Catla catla||Viet Nam||1980||Widely||Unknown||Unknown||Beneficial|
|Java tilapia||Oreochromis mossambicus||Viet Nam||1980||Widely||Yes||in reservoir||Beneficial|
|Nile tilapia||Oreochromis niloticus||Viet Nam||1980||Widely||Yes||in reservoir||Beneficial|
|Red tilapia||O. niloticus x O. mossambicus||Thailand||1991||Widely||Unknown||Unknown||Beneficial|
|Hybrid catfish||Clarias gariepinus x macrocephalus||Viet Nam||1981||Widely||Unknown||Unknown||Beneficial|
|African catfish||Clarias gariepinus||Viet Nam||1981||Widely||Unknown||Probably yes||Beneficial|
|Giant gourami||Osphronemus gouramy||Viet Nam||2000||Few||No||Unknown||Beneficial|
|Pomacea canaliculata||Asia||1990 1999||Rarely||Unknown||Adverse||Adverse|
|Silver pacu||Piaractus brachypomus||Viet Nam||2003||Unknown||Unknown||Unknown||Unknown|
|Cuban crocodile||Crocodilus rhombiser||Viet Nam||1986||Widely||Unknown||Unknown||Beneficial|
|Golden snail||Pomacea sp.||Thailand Viet Nam||1985 2001||Few||Yes||Adverse||Unknown|
Table 2. Recorded number of exotic species in the Mekong River mainstream and its tributaries
|Species Name||Total Riparian Country Records||Total Cambodian Records||Provinces||Habitats||Remarks (for Cambodia only)|
|Hypophthalmichthys molitrix||57||27||Kratie, Stung Treng Kompong Cham, Kandal||Mekong River||40% do not know species name.|
60% call as Chinese carp, Trey linh (Thynnichthys thynnoides) and Trey Krum Sar (Osteochitus melanopleurus)
|Labeo rohita||52||25||Kratie, Stung Treng Kompong Cham, Kandal||Mekong River||60% do not know species name.|
40% call as Trey Krum (Osteochilus melanopleurus) , Chinese Krum, Ka Ek Tmar, Ka Ek Crahom (Morulius chrysophekadion)
|Cyprinus carpio||96||27||Kratie, Stung Treng Kompong Cham, Kandal||Mekong River||63% do not know species name.|
37% call as Trey Dong, Kachep, Panay, Keab Srong, Sawka keo or Trey Chen.
|Oreochromis niloticus sp.||40||4||Kratie, Stung Treng Kompong Cham, Kandal||Mekong River||75% do not know species name.|
25% call Tiger fish
|Hypophthalmichthys molitrix||22||18||Kandal, Kompong Chhnang Stung Treng, Ratanakiri, Mondokiri||Tonle Sap and trib., Se Kong, Se San trib. Srepok trib., Srepok tributary||55% do not know species name.|
40% call Trey linh Thom, linh Heu, or linh Kam 5% call silver carp
|Labeo rohita||26||18||Kandal, Kompong Chhnang Stung Treng, Ratanakiri Mondokiri||Tonle Sap and trib., Se Kong, Se San trib. Srepok trib., Srepok tributary||90% do not know species name.|
5% call Trey Kros (Osteochilus)
5% call silver carp
|Cyprinus carpio||9||Kandal, Kompong Chhnang Stung Treng, Ratanakiri, Mondokiri||Tonle Sap, Se San, Srepok trib., Srepok tributary||88% do not know species name.|
2% call Trey Pan Kov
Exotic fish species in fishing lot areas
This information on exotic species in fishing lot areas was gathered in the regions around Phnom Penh, and the provinces of Kandal, Kampong Cham, Siem Riep, and Battambang. Informal interviews were conducted with key participants including fishing lot researchers, fisherman, and fishing lot owners. The survey was focused on the annual production of exotic fish in fishing lot areas. The survey results are described below:
There is a fishing area in the outskirts of Phnom Penh City known as Chung Ek fishing lot or fishing lot number 1, which covers the area around Chung Ek Lake. The following four exotic species were caught in this area, common carp (Cyprinus carpio), bighead carp (Aristichthys nobilis), silver carp (Hypophthalmichthys molitrix), and tilapia (Oreochromis sp.)
During the fishing season of 1997–2000, the Chung Ek fishing lot reported capturing from 20–60 kg per year of these exotic species. As a result of the year 2000 fishery reform, this lot has been terminated and released to the fishing community. Recent communication with villagers fishing in this area indicate that the exotic species mix is predominately tilapia.
The exotic species production from fishing lot numbers 01, 03, 04, 05, 13, 14, 16, and 17 during the 1999–2000 harvest season was around 300 kg-500 kg/year. The catch was primarily common carp (Cyprinus carpio), Indian carp (Labeo rohita), and tilapia. Individual fish were small with sizes ranging from 0.2 kg to 1 kg per fish. Fishing gear included bag and seine nets, and catches occurred from January to March.
Kampong Cham Province
In Kampong Cham province during the fishing season of 1998–1999, exotic species caught in fishing lot number 10 included common carp (Cyprinus carpio), Indian carp (Labeo rohita), and tilapia. Approximately 50 to 60 Tilapia were captured per year with a size range from 0.3–0.5 kg/fish. Average sizes for the common and Indian carps were between 2–4kg/fish. Long, trough shaped bamboo traps are used in this fishery and the season extends from October through December.
Siem Riep Province
The quantity of exotic species caught from fishing lot numbers 04, 05, 06 and 07 in Siem Reap was approximately 1600 kg in 1997–1998, and only 720 kg in 2000–2001. The primary exotic species was Rohu (Labeo rohita), referred to by local people as “Indian carp”. Production statistics can be found in Table 3.
Table 3. Rohu (labeo rohita) production from fishing lot Numbers 4, 5, 6, 7 in Siem Reap Province 1997–2001
|Fishing lot Number||1997–98||1998–99||1999–00||2000–01|
|Weight (kg/head)||Quantity (kg)||Weight (kg/head)||Quantity (kg)||Weight (kg/head)||Quantity (kg)||Weight (kg/head)||Quantity (kg)|
Common ornamental fish species in Cambodia
Since the Angkor era of the 11th century the culture of ornamental fish culture has been a part of Cambodian tradition. Many famous authors in Cambodia such as Troeung Ngear and Pikho Som have written many pages about the beauty of fish in water. Some folk tales feature the wild gourami fish and many people are involved in the culture of this species. It is very popular for people to culture the Siamese fighting fish in small jars or bottles as a hobby and for competition, especially during the New Year's celebration.
Ornamental fish are mostly exotic species. Among 31 common ornamental fish species in Cambodia, there are 10 indigenous species and 21 exotic species. Exotic species are imported from Thailand, Viet Nam, Singapore and Malaysia. Some famous indigenous species like the Siamese fighting fish, or Trey Krim are also available in neighboring Thailand and Viet Nam. Tiger barbs (Trey Khlar) and the Asian bonytongue (Trey Tapowt) are expensive and popular fish which can also be found in neighboring countries. Exotic species such as angelfish, koi, and gold fish which are easily bred in aquaria without hormone treatments are not imported to any significant degree.
Socioeconomics often dictates the species of fish hobbyists will enjoy. Most people, especially government staff, use inexpensive seed like goldfish which are readily available. Wealthier hobbyists possess more expensive species such as the Golden Asian Bonytongue, also known as the golden arowana or dragonfish. These fish are reknowned for their beauty and good luck. As ownership of these fish for beauty and luck becomes more widespread, many people in the cities will be encouraged to culture them as a business. Businessmen currently import some exotic ornamental species from Thailand and Viet Nam, and also engage in local breeding programs for additional species. The culture of ornamental fish has been characterized as serving three purposes: 1.beauty, 2.small-scale business and 3.medium-scale business (Vaddhna, 1996).
Table 4. Exotic species caught in fishing lot Numbers 01, 02 and 03
|Fishing lot Number 01||Quantity Kg/year||Weight Kg/head||Quantity Kg/year||Weight Kg/head|
|Indian carp (Labeo rohita)||150||-||300||0.3–0.6|
|Common carp (Cyprinus carpio)||no record||-||130||0.2–0.5|
|Silver carp (Hypophthalmichthys molitrix)||no record||-||70||0.2–0.5|
|Fishing lot Number 02|
|Indian carp (Labeo rohita)||12.5||2–3||-||-|
|Common carp (Cyprinus carpio)||17||-||-||-|
|Silver carp (Hypophthalmichthys molitrix)||14||-||-||-|
|Fishing lot Number 03|
|Indian carp (Labeo rohita)||-||2.5–5||-||-|
|Silver carp (Hypophthalmichthys molitrix)||-||0.5||-||-|
* Exotic carps not identified to species
Impacts of introduced exotic species of fish
There is currently no well documented evidence of exotic species causing environmental risks in Cambodia. It is likely that exotic species in Cambodia are having both positive and negative impacts on various economies in the country, while one would anticipate that impacts on aquatic ecosystems and biodiversity would be detrimental. Introduced fish may hybridize with endemic fish species, alter habitats, impact water quality, compete for food and space, prey on native fish and result in the introduction of exotic parasites and diseases (Courtenay and Stauffer, 1984; Moyle et al., 1986 and Arthington, 1989).
Introduction of exotic fish species for aquaculture could improve protein supplies and create job opportunities, especially for the rural poor located far from natural water bodies in remote locations. Most exotic species introduced in Cambodia are easy to breed and grow very fast in pond environments with minimal inputs. On the other hand, introduction or aquaculture of exotic species in natural water bodies may reduce fishery catch.
There is no study in Cambodia documenting whether introduced fish have altered aquatic habitats or had other impacts on local species and populations. However, there are reports from elsewhere indicating that exotic species can change the biological, chemical and physical characteristics of local environments to the detriment of local species. Feeding behaviors of exotic fish that uproot plants and disturb sediments can impact prey items for indigenous fish that feed on organisms in lake or streambed sediments. The disturbance of bottom substrates by European carp (Cyprinus carpio) during feeding has been attributed to increased turbidity (McCrimmon, 1968). This has implications for other species that visually search for food and impacts photosynthetic abilities of plants. Loss of plants further destabilizes benthic sediments, water clarity continues to decline and the whole system spirals downward. Thus, environmental degradation results from loss of aquatic vegetation, erosion of riverbanks, increased water turbidity and higher nutrient levels. This can destroy habitat for native fish, invertebrates, and waterfowl.
Some introduced species compete aggressively with native species for food and space. Although some introduced fish successfully exhibit generalist feeding habits and trophic opportunism (Taylor et al., 1984; Arthington and Mitchell, 1986), considerable overlap in the diets of introduced and endemic fishes have been reported in many systems (Arthington,1989). Aggressive feeding of some species on certain plants could reduce their availability to local species. The decline of endemic fishes is most often reported in association with disturbed and polluted habitats. High reproductive rates of introduced species such as tilapia may easily result in offspring occupying space and using resources that would otherwise be available for use by endemic species. This is a serious concern, especially during the dry season when water is normally confined to small ponds.
Introduced species may prey on all life history stages of native fish including eggs, larvae, juveniles and adults. However, whether introduced species prey on local species is undocumented in Cambodia. Introductions of fish have been implicated in the importation of parasites and disease outbreaks. Although some parasites require intermediate hosts, many are not very host specific, and others have less complex life cycles.
Existing policies on introduction of fish species
There are currently no detailed guidelines or regulations covering the importation of exotic species for culture that address environmental impact studies or environmental standards for fish farms. As a result, the development of freshwater aquaculture raises concerns about the potential negative impacts of introduced alien species on native fish stocks. Existing laws and regulations do, however, require activities undertaken be in compliance with international law including CITES, SPS, and the law of importation of goods.
The Department of Fisheries encourages culturing exotic species in earthen ponds or cages with appropriate safeguards in order to avoid the escape of these species into natural water bodies. The culture of indigenous fish species is one of the options that the Department of Fisheries is considering to further replace exotic species in aquaculture.
Table 5. The common alien ornamental fish culture in Cambodia*
|No.||Common name||Scientific name||Families|
|1||Black Ghost Knife Fish||Sternarchus albifrons||Apteronotidae|
|2||Giant gourami||Ophronemus gouramy||Anabanidae|
|3||Pearl gourami||Trichogaster leeri||Anabatantidae|
|4||Red Finned Fish||Metynnis sp.||Characidae|
|5||Black Tetra Fish||Gymnocorymbus sp.||Characidae|
|9||Jewel cichlid||Hemichromis bimaculatus||Cichlidae|
|10||Tiger Botia||Botia macracantha||Cobitidae|
|13||Bellybarred pipefish||Hippichthys spicifer||Indostomidae|
|14||Midget sucker catfish||Hypostumus sp.||Loricariidae|
|15||Guppy of million fish||Poecilia sp.||Loricariidae|
|17||Badis||Badis badis burmanicus||Nandiae|
|18||Giant Arapaima||Arapaima gigas||Osteoglossidae|
|21||Malayan angel||Monodactylus argenteus||Toxotidae|
* The source and year of introduction of these ornamental fish is undocumented
Further plan for controlling alien species
Cambodia should have strict rules for importing exotic animals including fish into Cambodia.
Only species which have no negative impacts on the environment should be imported.
Cambodia should promote aquaculture of exotic species but not in proximity to natural water bodies.
The Ministry of Agriculture should prepare guidelines on the management and movement of fish and fish products.
Implementation of international and regional codes of conduct should be undertaken.
Aquaculture should be integrated with land use planning so that certain areas can be separated for aquaculture of exotic species.
Fish stocking programs must release only indigenous species.
More research should be carried out on the impacts of existing exotic species on the environment.
Conclusion and Recommendations
Through surveys in fishing lots, exotic species production in five areas has been documented at approximately 1500–2000 kg per fishing season. The catch comprised primarily common carp (Cyprinus carpio), bighead carp (Aristichthys nobilis), silver carp (Hypophthalmichthys molitrix), and tilapia (Oreochromis spp.). Exotic species are present in great numbers in natural habitats of the Mekong River and it's tributaries.
Given the landscape topography and seasonal flooding in the country, it is difficult for Cambodia to control the dispersal of alien fish in natural environments. Efforts to do so should involve collaboration among all countries within the greater Mekong/Langcang Basin.
There are no research programs in Cambodia to document annual production of exotic fish species in various habitats, or identify what impacts these exotics may have on other natural resources. As a result, if exotic species abundance increases in the future, it will be difficult to ascribe any changes in other natural resources to this increased abundance of exotic fish or other causes. This will complicate natural resource management. An impact assessment of exotic fish species in Cambodia should be developed. This would identify areas of concern, increase awareness, and improve the abilities of fisheries researchers and fisherman to identify alien species. A research program to study long-term impacts of exotic fish species on the environment and fisheries resources is very important for natural resource conservation and management.
Individual countries and their peoples have a responsibility help safeguard local environments from unwanted exotic fish species. The most important guideline to prevent alien fish from entering local environments is to not allow anyone to release exotic fish into waterways.
Arthington, A.H. 1989. Impacts of introduced and translocation of freshwater fishes in Australia, p. 7–20. 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. Publ. 3, X, Manila. Philippines. 132–173.
Arthington, A.H. & Mitchell, D.S. 1986. Aquatic invading species. In R.H. Grooves and J.J. Burdon (eds.) Ecology of Biological Invasions: an Australian Perspective,. Australian Academy of Science, Canberra. 34–52.
Courtenay, W.R. & Stauffer J.R. (eds.) 1984. Distribution, Biology and Management of Exotic Fishes. Johns Hopkins University Press, Baltimore.
Moyle, P.B., Li, H.W. & Barton, B.A. 1986. The Frankenstein effects. Impact of introduced fishes on native species in North America, In R.H. Stroud (ed.) Fish Culture in Fisheries Management. American Fisheries Society, Bethesda, MD. 1981. 415–426.
Nam, S., & Thuok, N. 1999. Cambodia Aquaculture Sector Review (1984–1999) and Outline of National Aquaculture Development Plan (2000–2020). APCU/DoF, Phnom Penh.
Rainboth, W.J. 1996. Fishes of the Cambodian Mekong. FAO Species Identification Field Guide for Fishery Purposes. FAO, Rome, 265 pp.
Taylor, J.N., Courtenay, W.R. & McCann, J.A. 1984. Known impacts of exotic fishes in the continental United States. In W.R. Courtney and J.R. Stauffer (eds.) Distribution, Biology and Management of Exotic Fishes. Johns Hopkins University Press, Baltimore. 132–173.
Vaddhna, E. 1996. Research on species of ornamental fish in Phnom Penh. Phnom Penh, Cambodia. A research study for fulfillment bachelor degree at Royal University of Agriculture.
|The benefits of introduced species are usually realized immediately, but the adverse effects of many exotic species surface after a long time|
Though the major aquatic organisms used in aquaculture in China are indigenous species, the introduction of alien species and genetic selection to improve cultured strains have a significant role in the development of aquaculture, such as increasing total aquaculture production, supplying new species for aquaculture to meet market demands, and increasing farmers' income.
The benefits of introduced species are usually realized immediately, but the adverse effects of many exotic species surface after a long time. Any movement of aquatic organisms between natural ecological boundaries (e.g. watersheds) may involve risk to biodiversity. There is need for refinement and wider application of protocols, risk assessment methods, and monitoring programs for introductions of alien fish species, including genetically improved strains. Internationally accepted codes and protocols exist for reducing the risk of transboundary movement of pathogens including parasites. These cover incidental transfer associated with the movement of fish including alien species, but they need to be better promoted to increase awareness. In China, the management of introduction of alien species has been strengthened since1991. This paper highlights the present status of introduced alien species in China, including their impacts, problems faced in fisheries and aquaculture, and related management issues.
Information on alien species introduction
Alien species and genotypes, such as tilapia, carps, rainbow trout, shrimp and prawns, are used throughout the world. The introduction or transfer of aquatic organisms in support of aquaculture and various fishing initiatives has recently increased quite rapidly. Although China is rich in endemic aquatic genetic resources, introduction of different varieties of alien aquatic species has taken place since the 1960s. To date, introductions for aquaculture purposes have included over 50 species of fish, approximately 10 species of crustaceans, 12species of mollusks, and 11 species of seaweed. Approximately 10% of these are important species in Chinese aquaculture (Table 1), and they comprise about 10% of national aquacultural production. The introduction of ornamental alien species is undertaken primarily by the private sector and there is no official record documenting these introductions. It is likely that more than 100 species of ornamental fish have been introduced.
Many species have been introduced illegally without pre-evaluation, quarantine, or post-evaluation. Only a few species were tested by research institutions before being released.
Table 1. Annual production of successfully introduced and cultured alien species in China
|500–1000 (× 103t)||100–500 (× 103t)||10–100 (× 103t)||1–10 (× 103t)|
|Tilapia(Oreochromis niloticus niloticus)||White shrimp (Litopenaeus vannamei)||Channel catfish (Ictalurus punctatus)||Red drum (Sciaenops ocellatus)|
|Scallop (Argopecten irradians irradians)||Giant freshwater prawn (Macrobrachium rosenbergii)||Pacu (Colossoma brachypomum)||Turbot (Psetta maxima)|
|Brown kelp (Laminaria japonica)||Tiger shrimp (Penaeus monodon)||Rainbow trout (Oncorhynchus mykiss)|
|Large mouth bass (Micropterus salmoides)|
|Africa catfish (Clarias gariepinus)|
Impact of introduction of alien species or genetically improved strains
Both positive and negative consequences can arise from introducing alien species. The following are a few notable examples from experiences in China:
The GIFT strain of Nile tilapia (Oreochromis niloticus niloticus) has been recognized as a genetically improved fish and been introduced into many Asian countries. Its performance was evaluated on research stations and farms in China between 1994 and 1996. It was revealed that growth of the GIFT strain fish was significantly higher (7–30%), and they were 2–3 times more likely to be caught than the existing Nile tilapia strains. This strain was certified as a good breed by regulatory authorities and distributed throughout China. Since 1996, further genetic selection through seven generations has resulted in an additional 30% increase in growth in comparison to the original strain introduced in 1994.
|The Chinese government will use the strongest possible measures to prevent unauthorized introductions|
The bay scallop (Argopecten irradians irradians) was introduced in the 1980s and formed a new industry with annual production of close to 1 million tons.
The white shrimp (Litopenaeus vannamei) was introduced in the 1990s and now is the dominant species of shrimp produced in China.
The turbot (Scophthalmus maximus) was introduced in 1992 and artificially reproduced in 1998. Because of its high value, turbot culture has developed into a significant industry in Northern China.
In 1992, there were great losses to shrimp production in China due to the outbreak of white spot viral disease. This was thought to be due to importation of virus infected shrimp post larvae from abroad.
Ecological Disturbance and Invasion
The river perch (Perca fluviatilis) is a carnivorous species introduced from the Ertrix River basin in the north Xiangjiang Autonomous Region to the Bosten Lake in the south Xiangjiang Autonomous Region for fishery resource enhancement. It became a dominant fish in the new environment and caused the extinction of native bighead (Apiorhynchus laticeps) and the decline of many other species.
The red swamp crayfish (Procambarus clarkii) was accidentally introduced during World War II from the USA. It appeared in catches in Shanghai suburbs in the 1960s, and then spread along the Yangtze River basin up to Chongqing City, where it reproduces in surrounding water bodies. In some areas, populations are so abundant they are consumed by people during a special festival and also harvested and processed for export. However, burrowing activity by the crayfish has damaged dikes and drainage systems by creating burrows as deep as 1.5meters which may weaken dikes and cause flooding.
Table 2. Aquatic alien species certified by NCCA
|Common name||Scientific name||Certification code|
|Nile tilapia||Oreochromis niloticus niloticus||GS03001–1996|
|Blue tilapia||Oreochromis aureus||GS03002–1996|
|Large mouth bass||Micropterus salmoides||GS03003–1996|
|Channel catfish||Ictalurus punctatus||GS03005–1996|
|Rainbow trout||Oncorhynchus mykiss||GS03006–1996|
|Rainbow trout (Donaldson strain)||Oncorhynchus mykiss||GS03007–1996|
|Leather catfish||Clarias lazera||GS03008–1996|
|German mirror common carp||Cyprinus carpio||GS03009–1996|
|Russia mirror common carp||Cyprinus carpio||GS03010–1996|
|Giant freshwater prawn||Macrobrachium rosenbergii||GS03012–1996|
|Bay scallop||Argopecten irradians irradians||GS03015–1996|
|Pacific oyster||Crassostrea gigas||GS03017–1996|
|Bigmouth buffalo||Ictiobus cyprinellus||GS03002–2000|
The piranha (Serrasalmus nattereri) was introduced from South America as an ornamental fish. This aggressive carnivorous fish is referred to as the “eat men fish”. It is easily propagated, and if released into natural waters could become established and decimate native fish populations. As a result of these concerns, this species was banned in 2003.
Hybridization has been reported between the Nile tilapia Oreochromis niloticus niloticus and blue tilapia Oreochromis aureus (Li and Cai, 1995). There has also been mixed breeding between populations of the same species representing different introductions.
Formulation of Policy and Strategies to Manage Introductions of Aquatic Alien Species
Certification of Introduction of Aquatic Alien Species
Before the 1990s, China did not have any specific act to prevent the illegal introduction and spread of introduced alien species. Since 1990, a guideline and step-by-step process on exotic introductions and quarantine of aquatic animals has been prepared. The National Certification Committee of Aquatic Wild and Bred Varieties (NCCA) was established in 1991 under the Ministry of Agriculture (MOA). One of its mandates is to certify genetically improved aquatic breeds and alien species for aquaculture. Only certified genetically improved fish breeds and alien species can be released for commercial aquaculture. The current list of genetically improved fish breeds and alien species certified by the NCCA for commercial aquaculture are listed in Table 2.
Management and Regulation of Aquatic Alien Species Introductions
Recently, a proposal for national regulations to manage introduction of aquatic alien species has been developed. The regulation includes two parts: 1) the text of the rule, and 2) A list of species by category. This proposed regulation would apply to all life stages, including broodstock, gametes, embryos, larvae or young animals, spores, and other genetic materials intended for use in breeding for purposes of aquaculture and enhancement. More detailed information about this proposal can be found at: http://www.chinabiodiversity.com/etf/annual-2002-en.htm#c
|Many species have been introduced illegally without pre-evaluation, quarantine, or post-evaluation. Only a few species were tested by research institutions before being released|
Proposals for any new introductions would be presented to the provincial and/or central government authority and should include:
Application report, including proposed place of introduction and objectives, area of origin, biological data (habitat, reproduction), cultivation system, disease condition, proposed number, size and life history stage.
Capacity of the applicants to carry out the introduction, estimated ecological (competition, predation, hybridization, pathogen transfer), social and economic impacts.
The local fishery management authorities would grant first approval.
Final approval is under administrative authority of the provincial or central government and depends on the category of animals proposed for introduction (see appendix II).
For new introductions, the Ministry of Agriculture will organize experts to evaluate the need and justification for the introduction. The Chinese government will use the strongest possible measures to prevent unauthorized introductions. For example, in early 2003 possession of the piranha Serrasalmus nattereri, originally imported from Brazil was prohibited throughout China.
Li Sifa and Cai Wanqi. 1995. Introgression in hatchery stocks of Tilapia nilotica and Tilapia aurea in China (in Chinese). J.-Fish.-China-Shuichan-Xuebao: 19(2): 105–111.
Category list for introduction of aquatic alien species
In this list, Class I species are forbidden to be introduced, Class II species are authorized if approved by the Ministry of Agriculture, Class III species are authorized if approved by the provincial fishery authorities. The Ministry of Agriculture has jurisdiction over species not on this list. Blank entries indicate data is unavailable or there is no English common name for the species.
|Common name Chinese/English||Scientific name||Origin Area/Country||Year of first introduction|
|Hypostomus plecostomus||South America||1990|
|/ Land snail||Ampullarium insularum||Taiwan|
|Acipenser baeri baeri||Russia||1998|
|/ Russian sturgeon||A. gueldenstaedti||Russia||1993|
Fringe barbel sturgeon
|A. nudiventris||Former USSR||1933|
|/ Sterlet||A. ruthenus||Russia||1997|
|Huso huso (♀) x A. ruthenus(♂)||Russia||1997|
|/ European eel||Anguilla anguilla||France||1990|
|/ American eel||Anguilla rostrata||USA|
|/ Short fin eel||Anguilla australis australis||Australia|
Giant mottled eel
|/ Giant gourami||Osphronemus goramy||Viet Nam||1996|
Siamese Tiger Fish
|/ Slider turtle||Trachemys scripta||Brazil||1997|
|/ Snapping turtle||Chelydra serpentina||USA||1997|
|/ Crowned river turtle||Hardella thurjii||Bangladesh, Pakistan|
Yellow-headed temple turtle
|Hieremys annandalei||Thailand, Malaysia|
Malayan snail-eating turtle
|Malayemys subtrijuga||Viet Nam, Thailand, Malaysia|
|/ Painted terrapin||Callagur borneoensis||Thailand, Malaysia|
|/ Pond turtle||Mauremys sp.||1997|
|SPF/ Kuruma prawn||Penaeus japonicus|
Pacific white shrimp
Australian Cray Fish, marron
|/ Red abalone||Haliotis rufescens||USA||1985|
|/ Green abalone||H. fulgens||USA||1985|
|/ Black abalone||H. discus discus||Japan||1996|
|/ Bloody clam||Tegillarca granosa||South Korea|
Green sea urchin
|/ Chum salmon||Oncorhynchus keta||Russia||1988|
|/ Pink salmon||O. gorbuscha||Russia||1987|
|/ Atlantic salmon||Salmo salar||USA||2001|
|/ Masu salmon||Oncorhynchus masou masou||Japan||1996|
|/ Rainbow trout||O. mykiss||North Korea||1959|
|/ Rainbow trout||O. mykiss||Japan||1996|
|/ Steelhead trout||O. mykiss||USA||2001|
|/ Brook trout||Salvelinus fontinalis||USA|
|/ Whitespotted char||Salvelinus leucomaenis||Japan||1996|
|/ Northern whitefish||Coregonus peled||Former USSR, North America||1985|
|C. lavaretus maraenoides||Former USSR, North America||1985|
|/ Broad whitefish||C. nasus||Former USSR||1987|
|/ Northern pike||Esox lucius||USSR|
|/ Tench||Tinca tinca||Czech||1997|
|/ Catla||Catla catla||Bangladesh||1983|
|/ Sultan fish||Leptobarbus hoevenii||Thailand||1988|
|/ Mrigal carp||Cirrhinus mrigala||India||1982|
|/ Rohu labeo||Labeo rohita||Thailand||1978|
|/ Mirror carp||Cyprinus carpio carpio||German||1984|
|/ Mirror carp||Cyprinus carpio carpio||Former USSR||1984|
|/ Mirror carp||Cyprinus carpio carpio||Former USSR||1958|
|/ Common carp||Cyprinus carpio||Former USSR||1958|
Common European carp
|/ Channel catfish||Ictalurus punctatus||USA||1984|
North African catfish
|/ Walking catfish||C. batrachus||Thailand||1978|
|. Sutchi catfish||Pangasius hypophthalumus||Thailand||1978|
|/ Giant catfish||Pangasianodon gigas||Thailand||1986|
|/ Wels catfish||Silurus glanis||German, Hungary||1990|
|/.Spotted gar||Lepisosteus oculatus||USA||1990|
|/ Walleye||Sander vitreus||Canada||1993|
|/ Silver perch||Bidyanus bidyanus||Taiwan||1998|
|/ White perch||Morone americana||USA|
|Morone saxatilis ♀x Morone chrysops ♂||USA||1993|
|/ Golden perch||Macquaria ambigua||Australia||1991|
|/ Zander||Sander lucioperca||Russia||1960|
Black spotted grenadier
|/ Yellow bass||Morone mississippiensis||USA|
|/ Barramundi||Lates calcarifer||Thailand||1983|
|/ Murray cod||Maccullochella peelii peelii||Australia||2001|
|/ Bluegill||Lepomis macrochirus||USA||1987|
|/ Green sunfish||L. cyanellus||USA||1999|
|Oreochromis mossambicus||Viet Nam||1957|
|/ Nile tilapia||O. nilotica||Sudan||1978|
|/ Blue tilapia||O. aurea||USA||1981|
|/ Mango tilapia||Sarotherodon galilaca||Africa|
Black chin tilapia
|O. mossambicus (♀) x O. nilotica nilotica (♂)||Taiwan||1983|
|O. Mossambicus (♀) x O. nilotica nilotica (♂)||Taiwan||1978|
GIFT Nile tilapia
|O. nilotica nilotica||Philippines||1994|
|/ Kawa anago||Eleotris oxycephala||Thailand, Viet Nam||1988, 1999|
|/ Sleeper||Oxyeleotris sp.||Thailand||1986|
Marble goby, sand goby
|/ Dusky sleeper||Eleotris fusca|
|/ Snakehead||Channa striata||Thailand||1986|
|/ Turbot||Psetta maxima (Scophthalmus maximus)||UK||1992|
|/ Southern flounder||Paralichthys lethostigma||USA||2002|
|/ Broad flounder||P. squamilentus|
|/ Puffer||Fugu ocellatus||Japan|
|/ Puffer||Fugu rubripes|
|/ Kuruma shrimp||Penaeus japonicus|
|/ Tiger shrimp||P. monodon||Thailand||1986|
Giant freshwater prawn
|./ Redclaw, yabby||Cherax quadricarinatus||Australia||1992|
|/ Bay scallop||Argopecten irradians irradians||USA||1981, 1982|
|/ Yesso scallop||Patinopecten yessoensis||Japan||1981|
Bay, Calico scallop
|Argopecten irradians concentricus||USA||1991|
Bay, Calico scallop
|Argopecten irradians concentricus||USA||1995|
|/ Pacific Oyster||Crassostrea gigas||Japan||1985|
|/ Atlantic Oyster||Crassostrea virginica||USA||1985|
|/ Blood, ark shell||Scapharca broughtonii|
|/ Spirulina||Oscillatoriaceae spirulina|
|/ Brown algae||Laminaria japonica||Japan||1930|
|/ Brown algae||Laminaria japonica||Japan||1982|
|/ Eucheuma||Eucheuma muricapum||Philippines||1985|
|/ Nori||Porphyra yezoensis||Japan||1991|
|/ Dunaliella||Dunaliella sp.||Israel||1991|
|/ Chlorella||Chlorella sp.||Japan||1995|
|/ Giant kelp||Macrocystis pyrifera||USA||1982|
|/ Tetraselmis||Tetraselmis sp.||Canada||1996|
and Kamphet Rodger
|Aquaculture development in Lao People's Democratic Republic is a combination of traditional methods and lessons learned from the neighbouring countries, such as China, Viet Nam and Thailand|
Policy formulation and strategies in fisheries are a recent development in Lao People's Democratic Republic, emerging over the past decade. More recently, interventions in fisheries have been directed towards the conservation of natural resources and the development of fish farming by decentralizing the fisheries management functions to local authorities. These activities have included:
awareness building on the adverse impacts on the use of illegal and destructive fishing gears;
promoting the sustainable exploitation and use of indigenous fish species;
the establishment of fish breeding facilities;
the use of non-carnivorous species in aquaculture;
the careful use of exotic species in aquaculture.
Previous fisheries management measures that have been enforced by local authorities and by communities themselves have often resulted in conflicts and problems because of the lack of scientific based information responding to the root causes of the situations. This situation started to improve through the guidance of the Prime Minister Decree No. 118 on 5October 1989 concerning the management and conservation of aquatic animals, wild animals, the hunting and fishing.
Fisheries management in Lao People's Democratic Republic in Nam Ngum reservoir has been assisted successively by many donors such as Netherlands, Switzerland, FAO and Denmark, through MRC since the beginning of the establishment of the Hydro-Power reservoir. mainly Netherlands, Switzerland, FAO and Denmark.
Aquaculture development in Lao People's Democratic Republic is a combination of traditional methods and lessons learned from the neighbouring countries, such as China, Viet Nam and Thailand. Fish seed farms were built in many provincial capitals during the Indochina war period, especially during 1960s with USAID assistance in Vientiane, Savannakhet, Pakse, Sayaboury and Luang Prabang. In early 1970s, hatcheries were constructed in northern provinces (Houa Phanh, Xieng Khouang and Oudomxay) with the assistance of China and Viet Nam. From 1997 onwards there were a number of external assistance projects. A FAO/UNDP intervention assisting the Government in aquaculture development in areas such as capacity building, extension, fish seed production demonstration, fish culture techniques, information on technologies, hatchery rehabilitation. By the end of 2001 throughout the country there were fish seed hatcheries scattered throughout 18 provinces of Lao People's Democratic Republic, 30 existing hatcheries in which 17 belong to provincial Government and 13 belong to private farms. There were nine new hatcheries under construction. Altogether, these hatcheries and their production will form the basic infrastructure for the expansion of aquaculture in the near future.
Fisheries Development Program
Throughout the development of fisheries sub sector and particularly aquaculture, the promotion of the introduction of exotic species for aquaculture was problematic due to lack of supply and the inability to maintain the broodstock in sufficient numbers and quality. Several projects have also been targeted at the use and exploration of indigenous species. More than 500 species out of 1200 species in the Mekong River Basin have been identified (Fish of Lao by Maurice Kottelat 2001) with the assistance of World Bank, IUCN and WWF. This elucidated the high degree of fish species diversity, even though it is still incomplete. In the field of aquaculture, checking only the available aquatic biodiversity that is currently being utilized, it was found that there are nine exotic species and around 18 indigenous species found in subsistence farming type aquaculture. .
Indigenous species found in aquaculture comprised of: Barbodes gonionotus (Pa pak), Channa micropeltes (pa do), Hampala macrolepidola (pa soud), Hemibagrus numerus (pa kod), Hemibagrus wyckioides (pa kheung), Pangassius kremfi (pa souay), Wallago leeri (pa khoune), Wallago attu (pa khao), Wallagodimina (pa khop), Osteochilus melanopleurus (pa nock khao), Cirrhinus molitorella (pa keng), Cirrhinus microlepis (pa phone), Labeo behri (pa va), Morulius chrysophekadion (pa phia), Probarbus jullieni (pa eun), Clarias spp. (pa duk na), Osphrosnemus exodon (pa men).
Of the exotic species that are typically found (Table 1) are the: major India Carps like: Labeo rohita, C. mrigala, Catla catla, Cyprinus carpio, some Chinese carps: Aristichthys nobilis, H. molitrix, Ctenopharryngadon idella and Oreochromis niloticaus.
In the aquaculture of indigenous Mekong fish species project (AIMS), Lao People's Democratic Republic has chosen to study seven species among 17 namely: Barbodes gonionotus, C. microlepis (by Km8 Pakse station), C. molitorella and Puntioplites falcifer (by Nah Luang station), Clarias macrocephalus, Morulius chrysophekadion, and Osphoronemus exodon (by Nam Huang station).
Fish farming systems and fish species
The main fish farming systems that are practiced in the country are: pond fish culture, integrated farming with livestock, rice cum fish culture and fish seed production. The above-mentioned fish farming systems are generally followed by farmers according to traditional methods that as prevail in their respective localities and according to their own experience and that of their neighbours. Other fish cultures systems are becoming increasingly popular in the country namely:
cage culture in the main stream of rivers and reservoirs,
hatchery and nursery farming systems,
fish stock enhancement in small water bodies.
The indigenous species currently being bred and cultured extensively by farmers are pa pak (Barbodes gonionotus); While the snakehead (Channa sp.), and Gouramy (Osphoronemus gourami) are cultured by few farmers.
Other species indigenous to the Mekong and its tributaries have been imported to Lao People's Democratic Republic from adjoining Thailand. Fingerlings of Barbodes gonionotus were introduced to the Nong Teng fish farm in 1978 from Nongkhai fisheries station (on the opposite bank of the Mekong River Thailand) and were successfully bred for the first time in Lao People's Democratic Republic in 1980. Subsequently pa eun (Probarbus jullieni), pa keng (Osteochilus prosemion), pa phone (Cirrhinus microlepis), pa kaho (Catlocarpio siamensis), pa hou mat (Pangassius larnaudii), pa phia (Morulius chrysophekadion), pa men (Osphoronemus gouramy) and pa suey (Pangassius hypothalamus) were also subsequently introduced for culture.
Table 1. Information on alien species in Lao People's Democratic Republic
|Fish Species||Date of first introduction||Origin||Reason||Ecological impact||Social economic impact|
|Catla catla||1977||Thailand/India||Aquaculture||Not destroy aquatic environment||None||Beneficial||Cannot breed in natural water bodies|
|Ctenopharyn-odon Idella||1977||China||Aquaculture||Probably yes||Cannot breed in natural water bodies|
|Cirrhinus mrigala||1977||Thailand/India||Aquaculture||Probably yes||Cannot breed in natural water bodies|
|Clarias gariepinus||1980||Viet Nam||Aquaculture||Yes||Low price, hybrid|
|Cyprinus carpio||1965||Thailand||Aquaculture||Yes||Beneficial, productive|
|Laobeo rohita||1965||Thailand||Aquaculture||Not destroy aquatic environment||None||Beneficial||Cannot breed in natural water bodies|
|Oreochomis mossambicus||1965||Thailand/Japan||Aquaculture||Yes||Beneficial||People prefer|
|Oreochromis niloticus||Unknown||Thailand||Aquaculture||Yes||Beneficial||People prefer|
|Pomacea canaliculata||1986||Thailand||Ornamental||Unknown||Loss of money (impact on rice cultivation)|
Apart from the import of indigenous species for culture, there is a long tradition of fish culture in paddy fields in northern parts of Lao People's Democratic Republic and the similarities with that practiced in surrounding countries (such as bordering provinces in Viet Nam and Yunnan, PR China) suggests that is has a long history in the region. Carassius carassius, known locally as “Pa fek” (or possibly Carassius auratus) is an exotic species that appears to be feral in northern Lao People's Democratic Republic in upland streams and paddy systems and has probably been introduced historically by the tribes in the mountains that practice rice fish culture. The common carp (Cyprinus carpio) is a more recent introduction to paddy filed culture, but again, may have been translocated by migrations of tribes between China, Viet Nam and Thailand and therefore its arrival in Lao People's Democratic Republic is not certain but may well extend back well over a century.
Pond fish culture
Pond culture is pursued as both polyculture and monoculture. There are 23 species of fresh water fish that are reportedly cultured in the country, of which the most popularly cultured species are: Tilapia (the strains are unknown and have been extensively mixed through serial introductions and movement), common carp (Cyprinus carpio as with Tilapia, this species has local coloured strains that may have along history, more recent introductions have been from development assistance activities and bilateral support form Hungary and Viet Nam), silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), grass carp (Ctenopharyngodon idella), Rohu (Labeo rohita), Mrigal (Cirrhinus mrigala), African catfish (Clarias gariepinus), Giant snake head (Channa micropeltes), silver barb (Barbodes gonionotus), Cirrhinus microlepis, Cirrhinus molitorella, Morulius chrysophekadion, Osphoronemus exodon and Clarias macrocephalus.
Integrated fish livestock farming
In addition to rice farming, livestock raising is a traditional practice in rural households. Fish culture with livestock (pig and poultry) has been introduced and is practiced by some farmers but is still relatively uncommon in the country -partly due to the tendency of small farmers to not pen livestock, limiting manure introduction directly to the pond. Fish production in demonstration areas where high levels of manure were delivered to the pond was increased from 100–500 kg/ha without integration to 1200–2500 kg/ha with integration (Gupta, 2000).
Rice cum fish culture
Traditionally Lao farmers caught wild fish from natural sources than introduced to their paddy fields. However due to declining fish supply from natural sources and given importance of rice farming, there is growing interest in recent years in integrating aquaculture with rice farming in the country. This form of aquaculture is quite common in the northern Lao People's Democratic Republic.
Cage fish culture
In recent year fish culture in cages is developed largely in the central part down to southern part of the country namely Vientiane Municipality, Vientiane province, Khammouane, Savannakhet and Champassak provinces. The farmers culture fish in cage in reservoir (Nam Ngum, Nam Houm, and Nam Xuang) and along the Mekong River, Ngum River. The most popular fingerings being raised are sex reversed Nile tilapia which are typically imported from hatcheries across the Mekong river in Thailand. The result from cage fish culture are quite encouraging so far to the farmer who do not have access to ponds.
Recommendation of the national workshop on the impact of exotic fish species in Lao People's Democratic Republic
The national workshop on the impact of exotic fish species in Lao People's Democratic Republic was conducted by the Department of Livestock and Fisheries of Lao People's Democratic Republic (DLF) and Asian Institute of Technology (AIT) with financial support from SIDA. The workshop was held in Thalat, Vientiane province from 22 to 24 November 2002.
The workshop reviewed the alien species currently cultured in Lao People's Democratic Republic (Table 1). The summary of this review is presented in Table 1.
Recognized that the introduction of introduced fish has positive impact to the socio-economy of the country and also has had impacts on aquatic resources.
Understood that grass carp, African catfish and common carp are a risk to aquatic environment. The meeting agreed that these alien species should not be released into water bodies without deep technical study.
Recognized that the importation of aquatic animal and aquatic plants are a high risk for the introduction of fish disease into the country. Therefore the country should consider an arrangement to establish regulations for controlling aquatic animals.
Recognized that due to the high risk of alien fish species, they should only be promoted in suitable areas that are secure enough to minimize impacts.
Recommended publishing of technical guidelines, regulations and policy on sustainable aquaculture and fisheries in order to reduce negative impacts of alien species and promote their positive impact.
Recommended appropriate conditions and methodologies in establishing the technical infrastructure for serving export and import services.
Noted that there was a need to enhance public awareness on the negative impact of import introduced aquatic animals and aquatic plants into the country nationwide, in order to ensure wide participation in their monitoring and management.
Recommended that there should be continuing studies to solve the anticipated problems of the future.
Realized that there was a need to study new indigenous aquatic animal species in order to develop economically in the future.
Future Plans and Cooperation
Lao People's Democratic Republic lists the following as important elements of a national plan on responsible use of alien species:
Study on new biogenetic resources and technologies.
Study on an appropriate environment for culture.
Assessments on aquatic animal and aquatic plant diseases.
Study on types of fish farming.
Study on the fish farming and fish feeding.
Study on the brood stock management and culture.
Study on culture of indigenous fish and promotion of indigenous species as for the ornamental fish market.
Regional Cooperation to promote the Plan includes:
exchange of information on health issues in aquatic animals and plants;
establishment of Set regional guidelines on quarantine and health certification;
immediately reporting to neighbouring countries on outbreaks of aquatic animal disease.