Production data from 2015 to mid-2024 for S. salar in the Los Lagos region included live and dead biomass, secondary and environmental mortalities (algal blooms, low oxygen), bacterial and viral mortalities, antimicrobial use per production cycle, and total sea lice (Caligus).
An Antimicrobial Consumption Index (ICA) was calculated as kilograms of antimicrobials used divided by total produced plus dead biomass (tonnes),and classified into quartiles (low to high). Patterns were described (Figure 1), and a PCA was performed on antimicrobials and production variables (Figure 2).
Most centers fell into the low-consumption category, though a consistent fraction remained high. PCA showed ICA, SRS, and florfenicol co-occurred, with high antimicrobial use mainly linked to SRS outbreaks. Florfenicol was also associated with higher biomass, while other antimicrobials showed weaker links to bacterial mortality or biomass. Overall, antimicrobial use was driven mainly by florfenicol, with no single factor explaining use independently.