Biochemical polymorphism in yellow catfish, Mystus nemurus (C&V), from Thailand

Yellow catfish, Mystus nemurus (Cuv. & VaL.), is becoming one of the major freshwater species farmed by aquaculturists in Southeast Asia. rt was of in terest to examine levels of genetic subpopulation differentiation among sam ples of this species obtained from parts of its range, as well as to compar e the genetics of wild and hatchery-bred fish. Horizontal starch gel electr ophoresis and histochemical staining techniques were used to examine geneti c variation within and among eight wild and one hatchery populations of M. nemurus from northern, northeastern, central and southern Thailand. Four ti ssues (heart, liver; kidney and muscle)from individual specimens were used to analyze variations at 23 protein-coding loci. Fifteen of the 23 loci exa mined (65.22%), namely ACP*, AAT-1*, EST-1*, EST-2*, GPI*, IDH-1*, IDH-2*, MDH-1*, MDH-2*, MDH3*, ME*, PGM*, 6PGD*, SOD*, and HB*, were polymorphic at the 0.95 level. Observed heterozygosities ranged from 0.041 to 0.111, with an average of 0.068 +/- 0.028. Genetic distances ranged from 0.005 to 0.16 4. The greatest genetic distance was found between the Chainat and the Sura tthani populations (0.164), a level indicative of subspecific differenciati on in M. nemurus from within Thailand.