The phase of experimental pathogenicity in rainbow trout was implemented in line with the research project "Evaluation of the antibacterial effect of florfenicol (50%) produced in the country on rainbow trout produced at the Iranian Artemia Research Center", dated 28 November 2018. In this phase, the disease was experimentally induced in fish by intraperitoneal injection of liveYersinia ruckeri and the therapeutic effect of the drug produced in Iran will be studied on them.