Excessive Antibiotics

Large volumes of antibiotics are used in salmon farming to treat disease. Open net-cage aquaculture systems encourage antibiotic use because farmed fish are fully exposed to diseases and parasites that occur in the ocean environment.

With the combination of exposure to disease and the ability of disease pathogens to multiply quickly in the high density conditions common to net-cages, excessive and preventative antibiotic use is common practice in the salmon farming industry.

Farmed salmon are treated with antibiotics through medicated baths and medicated food. By law, a “withdrawal period” – a set number of days between the last use of the antibiotic and the harvest of fish for human consumption – must be met in order to limit the residues of antibiotics in the final product to safe levels.

The major cause of concern with the use of antibiotics in farmed salmon (and other livestock) is that many of these antibiotics are also used to treat human diseases. Frequent use of antibiotics in aquaculture and other industries poses a risk to human health by allowing disease microbes to become resistant to antibiotic treatments – making it more difficult to treat human disease.

Salmon Aquaculture Chemical Report

The multistakeholder World Wildlife Fund (WWF) Salmon Aquaculture Dialogue commissioned a report on chemical use in salmon farming.1 The committee of expert scientists that authored the report explain that:

“…this use of large volumes of antibiotics can only be explained by excessive and prophylactic [preventative] use. Excessive and prophylactic use of antibiotics in animal husbandry is in general the result of shortcomings in rearing methods and hygienic conditions that favor animal stress, and opportunistic infections and their dissemination.”

The committee of scientists, including a research scientist from Fisheries and Oceans Canada marine environmental sciences division, raised concerns about the large quantities of antibiotics that are applied in Chile and in BC. The quantity of antibiotics prescribed per metric ton of production is significantly higher in comparison to Norway or Scotland.

In open net-cage fish farming it is likely for antibiotics to pass into the environment, affecting wildlife remaining in the environment for extended periods of time. The report concludes that “antibiotic-resistant organisms in the marine environment will, in turn, pass their antibiotic resistance genes to other bacteria, including human and animal pathogens.” The whole ecosystem (including fish, shellfish, marine mammals, and human beings) is affected.

The industry continues to rely on these treatments, administered in net-cages open to the ocean, despite growing concerns over antibiotic resistance.2

Learn about closed containment systems and how they may offer a promising solution to the excessive use of antibiotics.


1 Burridge, Les, Judith Weis, Felipe Cabello and Jaime Pizarro (March 2008). Chemical Use in Salmon Aquaculture: A Review of Current Practices and Possible Environmental Effects. World Wildlife Federation, Salmon Aquaculture Dialogue.

2 Cabello, F.C. (2006) Heavy use of prophylactic antibiotics in aquaculture: A growing problem for human and animal health and for the environment. Environmental Microbiology. 8(7):1137-1144.