There's also the Vital Choices newsletter's Chile’s Salmon Farms Accused of Drug and Worker Abuses:

Regulations adopted by the United States and European Union restrict the use of antibiotics in salmon farming fairly strictly. But Chilean salmon farms are said to employ these vital human drugs in massive doses.

According to Ecoceanos and other sources, Chilean farms use 75 to 100 times more antibiotics per ton of salmon, compared with Norwegian farms.

Overuse of antibiotics can result in rising salmon-infection rates from antibiotic-resistant bacteria, and contamination of salmon steaks and fillets with antibiotic residues that can promote growth of drug-resistant bacteria in human diners.