resistance rates to these three antibiotics were all higher than 30%. Moreover, high levels of F (96.7%) and RA (80.0%) resistance were found in strains from diseased oysters. Thus, monthly F resistance rates should be monitored because such rates were obviously higher than those for the other tested antibiotics. The percentages of multi-resistance strains were also high and the peak were all more than 60% in farming seawater and in oysters. During the whole year, the antibiotic resistance peak s of the strains mostly overlapped in April, September, and November. Further studies are required to explain this seasonal occurrence of high antibiotic resistance among strains. In addition, resistance rates of seawaterderived bacteria to the same antibiotics was close to that of oysterderived bacteria. And correlation analysis indicated that a significant and positive correlation existed between the seawaterderived strains and the oyster-derived strains. Incidentally, oysters are physiologically distinct from fi sh, but exhibit similar results in bacterial resistance involving their cultivation environments