The type and amount of use of antibiotics in aquaculture depends on farming practices, different local and national regulations and government enforcement ability.
Pathogens occur naturally in the freshwater and marine environments. As with all types of farming, the process of raising farmed finfish like salmon includes a number of animal husbandry practices to ensure good animal welfare, and that fish remain healthy throughout the production cycle. Practices include using high-quality nutritional feed, providing a low-stress growing environment and, when diagnostic tests demonstrate the need, veterinarian prescribed antibiotic treatments against bacterial pathogens.
In Canada, antibiotics can only be used when they are required to fight disease, never to stimulate growth. Veterinarians can only prescribe drug products to treat farmed fish that have been approved for legal sale by Health Canada according to the Food and Drugs Act. In the past, most bacterial pathogens affecting farmed finfish were treated with antibiotics. However, the majority of the bacterial diseases may now be prevented using vaccines. This change in practice has drastically reduced the quantities of antibiotics used, which also substantially reduces the risks of bacteria in the wild from becoming antibiotic-resistant. However, there are still some diseases (e.g., Yellow Mouth) where vaccine treatments have not been developed or where vaccine treatments are not always successful or available (e.g. Bacterial Kidney Disease). In these cases farmers still rely on antibiotics to treat infected animals.
Norway has cut antibiotic use in salmon—one of the principal foods consumed in the country and a major export—to virtually zero. This has led to a flourishing industry and a reduction in the risk of antibiotic resistance in humans.