An Ecological Study of Edwardsiella tarda in Flounder Farm

Abstract

Edwardsiella tarda, a well-known freshwater fish pathogen, has been recognized as an important pathogen of marine fish recently. Flounder (Paralichthys olivaceus) is one of such species. For elucidating the ecology of E. tarda in marine environment, the distribution of the bacterium in a flounder farm in Nagasaki city was examined in 1985 and 1986 by means of direct plating method on SS (Salmonella and Shigella) agar and enrichment culture method in DSSS (WYATT et al., 1979) and strontium chloride B (IVESON, 1971) medium. E. tarda was hardly detected from sea water or fouling materials on net cages except for during epizootic, but was isolated everytime from the intestines of 10 to 50% of apparently healthy flounder. During the epizootic the incidence of E. tarda in the intestines rose to 60 to 100% of the samples. When the numder of E. tarda in the intestines rose more than 103 CFU/g, the bacterium was also tend to isolate from the kidney. All of 13 selected isolates from environment and the intestines were found to be virulent to eel. © 1988, The Japanese Society of Fish Pathology. All rights reserved.