As they swam through the Discovery Islands near Campbell River, which are home to 19 fish farms, the salmon were more likely to pick up the bacterium than in any other location along their route, the study suggests.

Scientist Andrew Bateman, lead author of the publication, argued that the results mean fish farms should be kept from operating along the salmon's migratory route.

"If we are wanting to protect these Fraser River sockeyes, we need to give them the best shot that we can," said Bateman.