Two of the viruses were present in fish from the three sources, while one of the viruses was only found in farmed fish. Next, they screened for these viruses in farmed salmon, hatchery salmon and wild salmon to determine their distribution. looked for viruses in dead and dying salmon from farms and discovered three previously unknown viruses. used these technologies to look for new viruses in Pacific salmon.įirst, Mordecai et al. In the last ten years, advances in DNA sequencing technologies have led to the discovery of many new viruses, and Mordecai et al. One factor that may be involved in these declines is viral infection.
The last three decades have seen large declines in populations of Chinook and sockeye salmon. These fish play a central role in the coastal ecosystems of the Northeast Pacific, where they have supported Indigenous populations for thousands of years. Chinook and sockeye salmon are two such species. Keystone species are animals and plants that play a pivotal role in supporting the ecosystems they live in, making their conservation a high priority. The discovery in dead and dying farmed salmon of previously unrecognised viruses that are also widely distributed in wild salmon, emphasizes the potential role that viral disease may play in the population dynamics of wild fish stocks, and the threat that these viruses may pose to aquaculture. Population surveys of >6000 wild juvenile Chinook and sockeye salmon showed divergent distributions of viruses, implying different epidemiological processes. In situ hybridisation localised arenavirus mostly to blood cells. Sequencing revealed two different arenavirus variants which each infect wild Chinook and sockeye salmon.
Metatranscriptomic sequencing and surveillance of dead and moribund cultured Chinook salmon revealed a novel arenavirus, reovirus and nidovirus. It is thought that infectious disease may contribute to declines, but little is known about viruses endemic to Pacific salmon. The collapse of iconic, keystone populations of sockeye ( Oncorhynchus nerka) and Chinook ( Oncorhynchus tshawytscha) salmon in the Northeast Pacific is of great concern.
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