Investigate the role of environmental andphysicochemical parameters affecting yersiniosisdisease in rainbow trout (Oncorhynchous mykiss) fshin the Haraz province

Yersiniosis or Enteric Red Mouth Disease (ERM) is an infectious bacterial disease that causes mortality and alsoeconomical loss in Salmonid aquaculture industries. In recent years, the yersiniosis has been expended in differentpart of Iran and there are reports about it in most of the Rainbow trout farms in Iran. Mazandaran Province hasthe second grade of Rainbow trout production in Iran and the most production of Mazandaran is in Haraz Zone(East of Mazandaran). There for, because of the importance of Yersiniosis and also high production of Rainbowtrout in this part of Mazandaran, factors influencing on yersiniosis incidence was evaluated. Samplings were donefrom July 2011 to August 2012 and in 10 rainbow trout farms. Overall, liverand kidney of 1200 fsh with clinicalsigns (410 samples) either without clinical signs (790 samples) were Cultured in TSA agar (Merck Co. Germany).Then Microbial cultures were transformed to laboratory (Ecology of Caspian Sea Institute, Health and Aquaticanimal’s Disease branch) and Bacteria were identifed using gram staining and biochemical tests. In addition, thewater of farms was sampled for calculating Bacterial total count and also measuring some of the physicochemicalparameters (Temperature, DO, pH, Nitrate, Nitrite, NH4+ and TDS) of water. Result showed that decrease oftemperature and increase of pH had the most effects on incidence of yersiniosis . Also, it was demonstrated thatfrom 410 diseased fsh and 790 fsh without clinical signs, 20% and 10% suffered from yersiniosis respectively.