Effect of government removal of salmon farms on sea lice infection of juvenile wild salmon in the Discovery Islands

Abstract

In response to a federal government order, the number of salmon farms operating in the Discovery Islands region declined from eight in 2020, to one in 2022. Over this period, 1627 juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon captured at sites throughout the study area were examined for sea lice. The average number of sea lice per juvenile salmon declined by 96% over the study period. Such a substantial decline was not witnessed in similar samples from the nearby Broughton Archipelago. The decline could not be attributed to chance sampling, and only a small proportion of it was associated with environmental fluctuations.