Current Status of Aquatic Genetic Resources Conservation and Utilization

in Thailand

Nuanmanee Pongthana

National Aquaculture Genetics Research Institute, Department of Fisheries, Thailand

Introduction

Thailand supports an extremely diverse aquatic fauna and flora along their supporting habitats. Situated in the Indo-Chinese and Malay Peninsula sub-regions of the Oriental Realm, the areas of the country has been described as a “Biogeographical Crossroad¡¨, where comprises Indo-Burmese, Indo-Chinese and Indo-Malayan elements. Thailand’s aquatic ecosystems are supported by two coastlines and six major river systems.

For at least 6,500 years, the economy of the Thai people in many parts of the country has been intimately involved with aquatic ecosystems. These ecosystems have been important not only as a source of water but also a source of food. In recent decades, Thailand’s economic growth has accelerated with the land developments, industrialization and cultivation combined with intensive human use of freshwater and marine habitats which remained, leading to significant threats to habitats, species and genetic diversities.

Biodiversity of aquatic resources in Thailand

Thailand extends from 50¡¦ N to 20o 30¡¦ N and from 97o 30¡¦ E to 105o 45¡¦ E and approximately 1,500 km from north to south and 800 km from east to west, covering 513,517 km². The North lies between the Salween and Mekong River systems and most of the area is drained by the headwaters of the Chao Phraya River system. The Northeast area drains almost entirely into the Mekong River system. The Central part has been watered by the mainstream of the Maeklong, Chao Phaya and Bangpakong Rivers. The Maeklong system, including the Kwae Noi and Kwae Yai, originated from the Tennasserim range of the westernmost areas. The Peninsula Thailand refers to the area south of 12o N latitude of southward from the Isthmus of Kra.

The Gulf of Thailand faces to the western part of the South China Sea to the northwest of the Indo-Malayan Peninsula. The eastern Gulf of Thailand has an area of 320,000 km² and a coastline of 1,874 km. In the west is the Andaman Sea with an area of 116,280 km² and a coastline of 740 km.

The major inland resources available for freshwater aquaculture and fisheries comprises 66 rivers, 10,233 lakes and swamps, 685 reservoirs and man-made lakes with the total water surface of 566,400 hectares. The six major river drainages are: the Salween, Mekong, rivers of southern Peninsula, southeastern part, Chao Phraya and Maeklong River systems.

The Salween River originates in the Tibethan range of the eastern Himalayas, and covers 324,000 km² of the drainage area. The river drainages pass through western Yunnan, China, and passes the Thai-Myanmar border and then runs off to the Andaman Sea at Martaban Bay. The Salween River system supports a unique Indo-Burmese fauna which is different from the other river systems in the country, but share similarities with the Ganges and Irrawaddi River faunas. At least 29 species are exclusively found in the river, (endemic), including cyprinids (Rohtee alfrediana, Aspidoparia morrah, Hampala salweenensis); catfishes (Aoriithys seenghala, Hemibagrus microphthalmus, Gagata sp., Exostoma vinciguerri, Pseudoechenius sulcatus); spiny eels (Mastacembelus alboguttatus); glassperch (Parambassis wollmeri) etc.

The Maeklong River system includes the Petchburi River and other drainages above the Ishmus of Kra, the Rivers originated from the eastern side of Tennaserim Range and runs off to the Gulf of Thailand. The watersheds have been supported by the vast areas of the western rain forest. Over 144 fish species were found.

Peninsula Thailand supports Indo-Malayan fauna and flora, with affinities toward the south. The area commences southward of the Ishmus of Kra, extending throughout the Malay Peninsula. The two mountains ranges of the southern Tennaserim and Khao Bantad, which receive Thailand’s highest rainfall, are the backbone of the Peninsula. The Khao Bantad Range supports the most extensive river systems. Six main but short river systems drain the Peninsula, three Rivers runs off to the Gulf of Thailand, and two Rivers drain to the Andaman Sea. Over 140 fish species were found.

Rivers of the southeast Thailand covers less extensive area of the southeastern part of the country, drained by relatively short mainstreams of three rivers. This is one of least seasonal area in Thailand, similar to the Peninsula both in the aspect of climatic and species occurrence. At least 120 freshwater fishes occurs, four species are exclusive to the area; Koh Chang Loach Schistura kochangensis, Myers’s Loach Pangio myersi, cyprinid Oreiichthys parvus and Mouth-brooder Betta Betta prima. More examples of affinity to the Peninsula are Asian Bony-tongue Scleropages formosus, Dwarf Rasbora Boraras maculata and Torrent stream Catfish Pterocryptis torrentis.

The Chao Phraya River system is the main blood vessels of the northern and central continental Thailand, originated from watersheds of the two mountains ranges. The system has been drained into by four major rivers; Ping, Wang, Yom and Nan Rivers, conjuncted into mainstream of Chao Phraya River at Nakonsawan. The River connects with three tributaries; Sakaekrung and Tachin from western, Pasak from the Petchabun Range, northeastern and Bangpakong from the Bantad Range, southeastern, then the system runs off to the Gulf of Thailand.

So far, 250 species of fishes are known but two catfishes thought to be endemic species, schilbeid Platytropius siamensis and mountain-stream sisorid Oreoglanis siamensis, both considered as a risk while the former species is thought to be on the brink of extinction. The Banpakong River, eastern tributary is an important habitat of the relict stock of the Chao Phraya fish species, whereas several species which disappeared from the mainstream i.e. Albulichthys albuloides, Macrochiricthys macrochirus, Cyclocheilicthys heteronema still rarely occur in this River.

The Mekong River is ranked as the 11^th longest world’s rivers. Originated from the eastern Tibethan Plateau, drained through six countries; China, Myanmar, Laos PDR, Thailand, Kampuchea, along 4,200 km, then runs off to the South China Sea at the Mekong Delta of southern Vietnam. Over half of the River length has drained through Thailand consists ca. 77% of the entire basin area. There are three main tributaries; the Chi-Mun Rivers of Northeast Thailand, the Nam Nguem and Nam Teun Rivers of Laos PDR and the Tonle Sap River of Kampuchea where connected with the Grand Lake.

The Mekong River system is inhabited by over 1000 species of fish. In the Thai portion, the River possesses at least 289 species. Some Chinese species affinity may occur, i.e. mud gudgean Abbottina rivularis, loach Sinibotia longiventralis and bagrid catfish Mystus pleuriradiatus. Over 30 fish species are endemic to this river, ranges from the largest Giant Catfish Pangasianodon gigas of the mainstream, to the 3^rd smallest cyprinid Boraras micros of the marshland.

The recent checklist reported at least 17 orders, 56 families and 570 species of freshwater fishes occur to Thailand, the largest family is Cyprinidae, possesses 204 species. The second is Balitoridae, 62 species known and Cobitidae, 31 species respectively. The River system which supports largest species number of the country is the Chao Phraya River, from which 329 species known. The Mekong basin of Thailand possesses 290 species; at least 270 fish species found in the Peninsula Thailand; the Maeklong basin possesses at least 207 species; the Southeast Thailand is found 166 species. The least species number is reported from the Salween basin of the country of 111 species. Additionally 15 introduced or exotic freshwater fish species was populated or flourished in natural waters (Table 1).

Aquatic resources utilization in Thailand

In Thailand, capture fishery accounts for the bulk or 52% of the total production, while the rest or 48% production comes from aquaculture. Marine fisheries accounts for 94% of the total capture fishery, while coastal aquaculture accounts for 79% of the total aquaculture production. Coastal aquaculture covers the production areas of 749.416 km², while freshwater culture covers the production areas of 583.992 km². The total fish production in 1995 was 3.5726 million tons with a total value of US$ 2,402.79 million. Part of the production is for domestic consumption, the rest is for export. In 1995, the exported quantity was 1,192,560 tons with a total exported value of US$ 29.14445 million.

Importance of aquatic genetic resource conservation to Thailand

The need for genetically improved aquaculture broodstock in Thailand is now widely recognized as natural populations of aquatic animals are fished out nearly to the point of extinction, and aquaculture supplies an increasing proportion of the food protein requirements of rural peoples. The value of genetic conservation in aquaculture has been recognized more recently.

Due to the conservation strategy for any aquatic species depends on its biology, genetic diversity within and between different populations and stresses that are modifying each population. One of the impediment to conservation of fish germplasm resources of Thailand is the lack of database on the above aspects. Genetic information is inadequate and biological information from different geographic populations of each species is limited.

Due to the high demand of large population and the rapidly developing aquaculture industry, aquatic biodiversity in Thailand is under a very high stress. Loss of biodiversity throughout Thailand may severely limit the sustainable development of aquaculture and fisheries. Genetic conservation of aquatic organisms becomes a critical problem for the sustainable development of aquaculture industry. Some efforts have been made by the government and fisheries scientists, but not much.

Impacts of hatchery stocks on wild fish has been realized. Due to hatchery breeding and rearing practices, the genetic variation and life history traits of farmed fishes differ considerably from wild fish. Broodstocks maintained for hatchery operations are subject to artificial selection for production traits or unintended selection at the time of establishing founder stocks or during domestication. Selection for specific traits generally result in reduced genetic variance and fitness. Due to massive introduction of cultured fish, displacement of wild stocks may be found and high levels of introgression of the altered hatchery fish genome into wild stocks may be taken place and may have serious implications for long term survival of wild stocks. Escape of farmed fish and inter breeding with wild populations can result in decreased fitness of wild stocks.

In Thailand, specific studies to show the genetic consequences of hatchery stocks on wild fish is lacking. Due to the ongoing programs of the Department of Fisheries for stocking reservoirs and rivers with hatchery bred seed of various fish species, the level of introgression is different between hatcheries may threaten the genetic purity and variability of wild stocks. Also, by stocking natural waters with hatchery seed from broodstock originating from a different geographic area, there is danger of homogenization of natural genetic diversity. The immediate requirement is to develop a breeding strategy that can be easily applied in commercial hatcheries to avoid inadvertent selection, inbreeding and introgression. Seed for ranching operations should be derived from wild stocks of that particular geographic area to avoid dilution of natural genetic.

In conclusion, most of the conservation efforts in Thailand are targeted at the level of ecosystem or species. Based on the genetic variation within and between populations, a species has the capacity to adopt to varying environmental conditions. Also the genetic variability within a species forms the foundation on which genetic upgradation programs can be based. Therefore, there is urgent need to take effective steps to safeguard against negative genetic consequences of escaped farmed fish.

Status of aquatic genetic resource conservation and utilization in Thailand

Conservation of aquatic genetic resources that prevent the deterioration of environments and regulate harvesting, culturing and transfers and introductions has recently become a national priority to avert the loss of many important aquatic species.

Thailand’s current and future aquatic genetic resources activities comprise the following:

¡PCharacterization and evaluation of aquatic genetic resources.

¡P Baseline information, performance recording and molecular characterization in many cultured aquatic species, i.e. carp species, marine shrimp, oysters, catfishes, freshwater prawn, etc.

¡PConservation/utilization of aquatic genetic resources, with sustainable use.

¡P In situ conservation via restrictions on fishing gear, times and season for the marine and freshwater resources.

¡P Ex situ conservation via developing of cryopreservation protocols in many cultured aquatic species, i.e. catfishes, carps, marine fishes, etc. as well as in genetically improved breeds of Silver barb and catfish for further dissemination

¡P germplasm transfers of genetically improved tilapia and common carp.

¡P Development of the national database on the diversity of aquatic species.

¡P A member of an International Network on Genetics in Aquaculture (INGA).

¡P Management of enhanced fisheries and aquaculture.

¡P Policy of property rights, national legislation/control on aquatic genetic resources.

Table 1. List of introduced or exotic freshwater fishes available in Thailand.

Species list	Year introduced	Introduced from	Origin
Family Cyprinidae
Cyprinus carpio Linnaeus, 1758	1912	China	China
Carassius auratus Linnaeus, 1758	1980	Japan	China
Ctenopharyngodon idellus Valenciennes, 1842	1922	China	China
Hypophthalmicthys molitrix Valenciennes, 1844	1932	China	China
Hypophthalmicthys nobilis Richardson 1844	1922	China	China
Labeo rohita Hamilton 1822	1968	India	Ganges basin
Cirrhina mrigla Hamilton 1822	1980	Bangladesh	Ganges basin
Family Characidae
Colossoma bidens Spix 1829	1980	Hongkong	Amazonia
Family Ictaluridae
Ictalurus punctatus Rafinesque 1818	1981	USA	USA
Family Clariidae
Clarias gareipinus Burchell 1822	1985	Laos PDR	Africa
Family Loricaridae
Hypostomus plecostomus Linnaeus 1758	1977	Hongkong	Amazonia
Family Cichidae
Oreochromis mossambicus Peters 1852	1948	Malaysia	Africa
Oreochromis niloticus Linnaeus 1758	1965	Japan	Nile basin
Oreochromis aureus Steindachner 1864	1957	Belgium	Africa
Family Poecilidae
Poecilia reticulata Peters 1859	1947	Singapore	Central America
Gambusia affinis Baird and Girald 1853	1947	Belgium	Central America