en Viral Diseases and viology Viral Diseases and viology پژوهشي Original research papers <div style="text-align: justify;">In the year 2017, Iran had fisheries production amounted to 1 million tons, of which the total aquaculture was about 300 thousand tons that 160 thousand tons of aquaculture was regarding <em>Oncorhynchus mykiss</em>. Increase of fish stocking density in the pond results in escalation of the number of nutrients, the stresses and incidence of diseases. Among these diseases viral diseases could be identified in the field of rearing ponds, such as Infectious hematopoietic necrosis (IHN), Viral Hemorrhagic Septicemia (VHS) and Infectious Pancreatic Necrosis (IPN). Unlike other projects that sample is taken from fish tissues known as a sample, in this study each farm was selected as a research unit<span dir="RTL">.</span>&nbsp;According to the layout of the work based on different fields; the positive or negative result of the presence of the pathogens was recorded. &nbsp;However, aquatic samples were collected from Mazandaran province and Yasuj sites, located in north and southwest of Iran, respectively. Based on the results of Mazandaran area, it was revealed that the increase of bio-safety in the pre-broodstock farms did not have a significant difference (p> 0.05) compared with the increase of immunity level or serum antibodies. This index was relatively equal in fish of other areas. Contrarily, in the pre-broodstock farms, the lysozyme value as a non-specific immunity index had a significant increase, which indicates that the upgrading of the bio-safety level can reduce stress and shift the energy directly to the production.<br> &nbsp;</div> Rainbow trout, SPF, IPN, VHS, IHN, Iran 71 82 http://ijaah.ir/browse.php?a_code=A-10-35-50&slc_lang=en&sid=1 M.J Zorriehzahra zorrieh@yahoo.com 10031947532846002516 10031947532846002516 No Aquatic Animal Health and Diseases Department, Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organization, Tehran, Iran S Kakoolaki bsh443@gmail.com 10031947532846002517 10031947532846002517 Yes Aquatic Animal Health and Diseases Department, Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organization, Tehran, Iran M Mehrabi bsh443@gmail.com 10031947532846002518 10031947532846002518 No Aquatic Animal Health and Diseases Department, Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organization, Tehran, Iran A Sepahdari asepahdari@yahoo.com 10031947532846002519 10031947532846002519 No Aquatic Animal Health and Diseases Department, Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organization, Tehran, Iran M Ghasemi bsh443@gmail.com 10031947532846002520 10031947532846002520 No Aquatic Animal Health and Diseases Department, Inland Water Aquaculture Research Center, Agricultural Research Education and Extension Organization, Anzali, Iran M Yarmohammadi bsh443@gmail.com 10031947532846002521 10031947532846002521 No Genetic Department, International Sturgeon Research Institute, Agricultural Research Education and Extension Organization, Rasht, Iran M Ghiasi bsh443@gmail.com 10031947532846002522 10031947532846002522 No Department of Aquatic Animals Health and Diseases, Ecology Research Center of the Caspian Sea, Agricultural Research, Education and Extension Organization, Sari, Iran