The physiological associations between infectious agents and migrating juvenile Chinook salmon (Oncorhynchus tshawytscha)

The role of infectious diseases in the declining productivity of wild Chinook salmon (Oncorhynchus tshawytscha) in BC is poorly understood. In wild populations, it is difficult to study the effects of infectious diseases because they interact with environmentally induced stress and diseased fish are not often observed as many are likely predated upon or die out of view. The early marine life of Pacific salmon (Oncorhynchus spp.) is believed to be one of the key components of the declining populations. More focus on understanding the potential role of infectious agents during this life period is needed. My study assessed how infectious agents are associated with the physiology of migrating juvenile Chinook salmon upon their entry to marine waters by linking ancillary data, physiological responses and histopathological lesions with infectious agent detection. It is one of the first to study infectious agents carried by wild salmon through combining molecular, protein, and cellular levels of fish physiology information. Among 46 assayed infectious agent taxa, 26 were detected, including viruses, bacteria, and parasites. Fish from Columbia River system were found to have significantly higher infection burden than those derived from five other regional groups. I discovered and reported the associations between fish physiological conditions and five infectious agents, including Ichthyophonus hoferi, ‘Candidatus Branchiomonas cysticola’, Parvicapsula minibicornis, Ceratonova shasta, and Piscine orthoreovirus (PRV). PRV, particularly, was recently reported in many salmon farms in BC as the suspected causal agent of two related diseases in both Atlantic and Chinook salmon, and has potential to be exchanged between farmed and wild populations. I further provided one of the first lines of evidence of potential impacts of PRV both on host genes and histopathology in the wild juvenile Chinook salmon. Understanding the relationships between infectious agents and salmon can help inform conservation and management practices.Forestry, Faculty ofGraduat