In 2018 the Clayoquot Sound UNESCO Biosphere Region saw salmon lice reach levels never seen before on the BC coast.
The source of these pests was the open-net pen salmon farms which clutter local wild salmon migration routes. Because salmon farms rear fish in crowded conditions, they act like lice incubators. The lice are then free to pass through the open nets to infest baby wild salmon, which would not normally encounter lice before they are old enough to have fully developed scales for protection.
A lice count of three or more per fish is the threshold for treatment on salmon farms. At one point, one of Norwegian-owned Cermaq’s Clayoquot farm sites reported lice levels of 54.7 per fish! With half a million fish per farm, that’s an explosion of 27 million lice—right when 2018’s tiny salmon smolts were migrating out of the rivers to their near-shore nurseries.