Genetic tool to track disease in B.C. salmon
By Randy Shore, Vancouver SunMarch 16, 2013
B.C. fishery scientists are developing a new generation of genetic tools to find diseases that are undermining the health of wild Pacific salmon and track them back to their source.
More than 90 per cent of juvenile salmon that migrate from fresh water to live as adults in the ocean die before they return to spawn, according to the researchers.
Disease is believed to be responsible for excessive mortality, according to Brian Riddell, CEO of the Pacific Salmon Foundation. But very little is known about the incidence of disease among wild salmon, in part because wild salmon are very difficult to observe once they enter the ocean and because weakened fish are eaten by predators, leaving no evidence of the cause of illness.
"We almost never see diseased wild fish," Riddell said.
But a new collaboration between Genome B.C., the PSF and Fisheries and Oceans Canada (DFO) is collecting the biggest set of tissue samples from both wild and ocean-farmed Pacific salmon ever assembled in order to analyze the genomes of all the viruses, disease and pathogens the fish carry.
Microbes accumulate DNA mutations through time, so the genome of a virus or other pathogen is like a trail of breadcrumbs that can lead researchers back to the source of infection.
Genetic testing tools being developed by DFO scientist Kristi Miller analyze samples for disease faster and in greater number.
"It will revolutionize our ability to do real-time (disease) surveillance," said Riddell.
The research could help satisfy several key recommendations for further research contained in the final report of Justice Bruce Cohen's commission on the health of the Fraser River sockeye. Cohen noted that pathogens and disease are strong contenders for causes of the decline of the Fraser sockeye and that disease transfer occurs between wild and farmed fish.
The first phase of the study is focused on collecting samples from known wild Pacific salmon populations all the way up the coast, concentrating at first on Fraser sockeye and chi-nook on B.C.'s south coast. Samples are also being collected from healthy fish in hatcheries and fish farms.
As the study progresses, new sample data will be collected each year over a one-month period to create a biological "snapshot" of the presence and distribution of potentially harmful pathogens in wild and cultured salmon populations.
rshore@vancouversun.com© Copyright (c) The Vancouver Sun
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