**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** INFECTIOUS HEMATOPOIETIC NECROSIS VIRUS (IHNV) IS A WIDESPREAD PROBLEM FOR THE RAINBOW TROUT (ONCORHYNCHUS MYKISS) AQUACULTURE INDUSTRY, RESULTING IN LARGE SCALE PRODUCTION LOSSES AND ECONOMIC HARDSHIP. SELECTIVE BREEDING OF FISH FOR RESISTANCE TO IHNV OFFERS A POWERFUL OPTION FOR MANAGEMENT OF THIS DEVASTATING PATHOGEN AND MITIGATION OF ITS IMPACTS. IN PARTICULAR, SELECTIVE BREEDING FOR FISH THAT ARE RESISTANT TO INFECTION AND TRANSMISSION IS LIKELY TO BE THE MOST EFFECTIVE STRATEGY, BECAUSE IT HAS THE POTENTIAL TO FACILITATE VIRUS ERADICATION FROM PRODUCTION FACILITIES. IN THIS PROJECT, WE PLAN TO QUANTIFY VARIATION IN IHNV TRANSMISSION RESISTANCE ACROSS RAINBOW TROUT GENETIC LINEAGES (FAMILIES) AND ESTIMATE THE HERITABILITY OF THE TRAIT. WE WILL THE DETERMINE IF TRANSMISSION RESISTANCE IS LINKED TO OTHER FARM PERFORMANCE TRAITS SUCH AS RESISTANCE TO CLINICAL DISEASE, GROWTH, YIELD, AND FILLET QUALITY. THIS WILL LAY THE FOUNDATION FOR FUTURE CAMPAIGNS TO SELECTIVE BREED RAINBOW TROUT FOR IHNV TRANSMISSION RESISTANCE. THE PROJECT WILL INVOLVE A PARTNERSHIP BETWEEN A LEADING EXPERT IN IHNV BIOLOGY, ANDREW WARGO, PHD AT THE VIRGINIA INSTITUTE OF MARINE SCIENCE, AND THE CHIEF SCIENCE OFFICER, JESSE TRUSHENSKI, PHD AT A LARGE RAINBOW TROUT AQUACULTURE COMPANY, RIVERENCE HOLDINGS. RESULTS WILL BE DISSEMINATED ACROSS THE SALMONID AQUACULTURE AND DISEASE MANAGEMENT COMMUNITIES THROUGH PRESENTATIONS AT PROFESSIONAL ASSOCIATIONS, INDUSTRY FORUMS, AND SCIENTIFIC MEETINGS; AS WELL AS THROUGH PUBLICATIONS IN TRADE AND SCIENTIFIC JOURNALS FOR DISSEMINATION TO THE LARGER COMMUNITY. COLLECTIVELY, THIS PROJECT WILL NOT ONLY BOLSTER IHNV MANAGEMENT IN SALMONID AQUACULTURE, BUT PROVIDE A FRAMEWORK FOR SELECTIVE BREEDING OF TRANSMISSION RESISTANCE THAT COULD BE APPLIED TO A VARIETY OF AQUACULTURE SYSTEMS.