Growth performance, survival and feed utilization of diploid (2n) and triploid (3n) sex-reversed male and female Nile tilapia were evaluated at maintenance feeding (1% body weight (BW) day À1 ), ¢xed feeding (3% BWday À1 ) and apparent satiation feeding levels in a freshwater recirculation system comprised of thirty-six1-m 3 concrete tanks at the Asian Institute of Technology, Bangkok,Thailand. Triploid Nile tilapia (3n) was produced by subjecting fertilized diploid (2n) tilapia eggs to heat shock. After hatching, ¢sh were sex-reversed to all-male and allfemale populations by oral administration of 17 amethyltestosterone (60 mg kg À1 feed) and ethynylestradiol (100 mg kg À1 feed) respectively.There was signi¢cantly higher growth with increased ration levels in both male and female groups. There were no signi¢cant di¡erences in ¢nal BW, spe-ci¢c growth rate, survival rate, feed conversion ratio and protein e⁄ciency ratio between diploid and triploid ¢sh. Triploids had lower gonad weights than diploids, and this was particularly evident at the satiation feeding level. Triploid ¢sh had a signi¢cantly higher apparent net protein utilization and percentage of gutted weight than diploids at all feeding levels. Higher protein utilization e⁄ciency of triploids might be an advantage for commercial tilapia culture but further research is necessary to make such a conclusion.

After more than 20 years of hatchery production of Asian seabass in Thailand, genetic information is still lacking for effective genetic management and a selective breeding programme. This study aimed to evaluate genetic status of existing hatchery populations and genetic consequences of a selective breeding attempt. We examined genetic relatedness in seven hatchery samples, including a selectively bred population (RACF-F1), compared with three wild samples using 11 microsatellite loci. Genetic diversity and relatedness values within most hatchery samples, except for RACF-F1, did not differ from those of wild populations (P > 0.05). RACF-F1 had the lowest allelic diversity and effective population size (A r = 6.99; N e = 7.8) and highest relatedness values (mean r xy = 0.075-0.204). Pairwise Φ ST values, principal component analysis and modelbased cluster analyses revealed three genetically distinct hatchery groups: Eastern Thailand (CHN, RACF, NSCF and SKCF), Southern Thailand (NICA) and the Andaman Sea (STCF). Results suggest that exiting domestic populations capture reasonable amount of genetic variation and can be useful for a base population for genetic improvement programmes. In addition, given the rapid increase in relatedness that we observed in one selectively bred population, we recommend using selection methods and hatchery practices that reduce variability in family contribution in the subsequent generations.

Population genetic structure of Varuna litterata living along the coast of Thailand were examined in this study. The samples were collected from 3 coastal regions: The Andaman sea

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