Cooperative Fish and Wildlife Research Units Program: Colorado
Education, Research and Technical Assistance for Managing Our Natural Resources

Since 2015, several state fish hatcheries in Colorado have had positive detections of Renibacterium salmoninarum, the causative agent for bacterial kidney disease (BKD) in salmonids. Since there is little known about the pathophysiology of inland trout, management efforts have been implemented at many hatcheries to reduce the transfer of this bacterium to offspring during spawning seasons. One management strategy is the removal of all fish once R. salmoninarum has been detected. However, it is unclear if depopulation of positive fish is necessary to eliminate the bacterium and, in many instances, critical and sometimes irreplaceable broodstocks are lost. The Colorado native greenback cutthroat trout (Oncorhynchus clarkii stomias) is one species of concern because depopulation may endanger populations of critical broodstocks. We are proposing to assess the bacterial load of R. salmoninarum within parents and evaluate the vertical transmission to progeny and to assist in developing non-lethal management strategies. We also propose to evaluate the consequences of keeping infected broodstock in a hatchery and the potential for horizontal transmission to other fish within the facility.