Review of Aquaculture Genetic Researches in Thailand

Aquaculture business has been well established in Thailand for more than 40 years. The most recent data indicated a total production of 260 380 tons. Sixty-five percent of the total production came from coastal aquaculture, mainly tiger prawn (Penaeus monodon) culture. Other important species for coastal aquaculture are banana prawn (P. merguensis), cockle (Anadara granosa), green mussel (Perna viridis), oyster (Crassostrea belcheri, Saccostrea commercialis), sea bass (Lates calcarifer) and grouper (Epinephelus tauvina). Freshwater aquaculture, although produced only 35% of the annual production, provides major protein source for people in rural areas. Important freshwater species are Nile tilapia (Oreochromis niloticus), tawes (Puntius gonionotus), sepat Siam (Trichogasterpectoralis), walking catfish (Glorias spp.), stripped catfish (Pangasius sutchi) and giant freshwater prawn (Macrobrachium rosenbergii). Optimum aquacultural practises, namely stocking density, nutrition requirement and water quality have been obtained in most cultured species. But genetic approach has not been considered, thus resulting in deterioration in economic traits which might be due to excessive inbreeding (reviewed by Uraiwan 1989) and/or negative selection (Wongsangchan 1985). The history of researches on genetics in aquaculture in Thailand started in 1982 when the aquaculture genetic programme in form of a network has been established at the National Inland Fisheries Institute, Department of Fisheries. This programme was supported by the International Development Research Centre (IDRC, Canada) in cooperation with Dalhousie University, Canada (Uraiwan 1989). In the same year a genetic improvement programme aiming at improving economic characters of some economic fish species has been conducted at the Department of Aquaculture, Kasetsart University. Paralelly a course in Fish Genetics has been offered. Since then different approaches of genetics have been applied with final objectives on improving aquaculture production of the country. Researches being conducted are reviewed according to the following fish species

MtDNA diversity of the critically endangered Mekong giant catfish (Pangasianodon gigas Chevey, 1913) and closely related species : implications for conservation

Catfishes of the family Pangasiidae are an important group that contributes significantly to the fisheries of the Mekong River basin. In recent times the populations of several catfish species have declined, thought to be due to overfishing and habitat changes brought about by anthropogenic influences. The Mekong giant catfish Pangasianodon gigas Chevey, 1913 is listed as Critically Endangered on the IUCN Red List. In the present study, we assessed the level of genetic diversity of nine catfish species using sequences of the large subunit of mitochondrial DNA (16S rRNA). Approximately 570 base pairs (bp) were sequenced from 672 individuals of nine species. In all species studied, haplotype diversity and nucleotide diversity ranged from 0.118&plusmn;0.101 to 0.667&plusmn;0.141 and from 0.0002&plusmn;0.0003 to 0.0016&plusmn;0.0013, respectively. Four haplotypes were detected among 16 samples from natural populations of the critically endangered Mekong giant catfish. The results, in spite of the limited sample size for some species investigated, indicated that the level of genetic variation observed in wild populations of the Mekong giant catfish (haplotype diversity=0.350&plusmn;0.148, nucleotide diversity=0.0009&plusmn;0.0008) is commensurate with that of some other related species. This finding indicates that (1) wild populations of the Mekong giant catfish might be more robust than currently thought or (2) present wild populations of this species carry a genetic signature of the historically larger population(s). Findings from this study also have important implications for conservation of the Mekong giant catfish, especially in designing and implementing artificial breeding programme for restocking purposes.</div