Factors affecting the spatial and temporal distribution of biofouling communities on Atlantic salmon (Salmo salar) farms: insights from the Broughton Archipelago, British Columbia, Canada.

Biofouling communities were examined at five depths at two salmon farms (Doctor Islets (DI), Wicklow Point (WP)) in British Columbia, Canada from April/May to October 2020. In addition, various water quality parameters were measured and the jellyfish numbers were quantified. Biofouling communities were mainly composed of Mollusca (primarily Mytilus spp.), arthropods (mostly harpacticoids), and hydroids (predominantly Obelia sp.), while jellyfish samples were made up mostly of medusa-form Obelia sp. At DI, all variables except ammonia were associated with biofouling counts, all variables except depth were associated with hydroid biomass, while only temperature, dissolved oxygen, ammonia, and nitrate were associated with jellyfish. At WP, all variables except phosphate and silica were associated with biofouling counts, only depth was associated with hydroid biomass, and only ammonia was associated with jellyfish. Insights into what environmental variables are correlated with biofouling organisms and jellyfish may assist with the development of effective mitigation strategies.