Salmon battle a coronavirus cousin

While the novel coronavirus continues to wreak havoc on the world above the water, salmon hatching in the Fraser Valley are facing their own crisis—including attacks from previously undocumented viruses. That’s tough news for a fish that has just experienced its worst year on record; the 2021 salmon run is expected to be a little better than 2020, but still not good enough to open up fisheries.

Among the problematic viruses is one known as the Pacific salmon nidovirus (PsNV). It is a cousin to coronaviruses found in mammals—like the one that upended the world in 2020—and causes damage to gill tissue while the salmon gets ready to transition to the ocean. It could compromise the ability of salmon to adapt to salt water, according to research done by federal scientist Kristi Miller-Saunders and others.

In BC, PsNV has been discovered most frequently in Chinook hatcheries in the Fraser Valley, although it was also found in 8% of wild Chinook and 18% of farmed Chinook. (PsNV was first found in wild Chinook after they had been in contact with hatchery-raised salmon.) A study showed the virus proliferated during the salmon’s development in freshwater and was then rarely detected in fish that had spent a month in the ocean—although it’s possible the salmon beat the infection, it’s more likely they died.

Miller-Saunders’ 2019 paper that identified the new virus also identified 2 other new kinds of viruses: an arenavirus, which causes lesions, and a reovirus, which causes bleeding. In general, little is known about viruses in salmon—it’s not clear how long PsNV has been around, for example, although there is evidence that it’s not brand new—but research shows the viruses definitely have a negative impact.

This week, Miller-Saunders told a meeting of the Standing Committee on Fisheries and Oceans that there’s no one solution to solving the crisis salmon are experiencing. Viral infections weaken salmon populations, as does travelling through warmer waters or hanging out near salmon farms. Fish who grow up in hatcheries also face issues related to domestication, which doesn’t make their transition to the ocean any easier.

“Hatchery fish don’t behave the same and they don’t survive the same as wild fish,” Miller-Saunders said. “So, if we can find ways of creating hatchery fish that have a very low level of stress and behave more like a wild fish, we could not only increase their potential for survival but we would decrease the domestic effects of hatcheries.”

Miller-Saunders and her team are planning to outfit some salmon with FIT-CHIPs, a type of biological marker that will allow researchers to see where salmon are experiencing the most stress. The hope is that this project will help identify what can be done to aid salmon throughout their lifecycle. If used in hatcheries, it could help smolts have a better chance of surviving out in the ocean—making it possible they could feed a hungry whale population, boost BC fisheries, or even make it back to the river to spawn.