Farmed salmon are fed more antibiotics
per pound than any other livestock in North America. Antibiotics are needed to control the spread of infection in the high
density conditions of open net-cage farms. According to B.C. government data, there has been an increase in the use of antibiotics per tonne of
production since 2001.
Escaped farmed fish caught in a Broughton Archipelago stream carried bacteria known to cause a range of human health problems. These bacteria were resistant to 10 different antibiotics. Excessive use of antibiotics has already led to the development of antibiotic resistant "super-bugs".
Excess drugs make their way along the food chain. Research suggests that between 74 to 100% of wild fish caught near farms contain antibiotics in their flesh.The Salmon Aquaculture Dialogue's report on chemical use states that “antibiotic-resistant organisms in the marine environment will pass their antibiotic resistance genes to other bacteria including human and animal pathogens. Thus the whole ecosystem (including fish, shellfish, marine mammals, and human beings) is affected.
The salmon farming industry often states that since antibiotic use by volume is significantly higher in other food production industries, the use (and excess use) of antibiotics in salmon aquaculture should be ignored. A committee of expert scientists disagree, including a senior staff member from Fisheries and Oceans Canada. In their report the committee of scientists explain that:
“[T]his use of large volumes of antibiotics can only be explained by excessive and prophylactic 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.”
SLICE
One of the most significant and well-studied impacts of salmon farming on wild salmon is the transfer of sea lice from fish farms to juvenile wild salmon during out-migration. Attempts to control sea lice outbreaks on salmon farms by industry and government have been through emamectin benzoate, sold under the commercial name SLICE. Emamectin benzoate, the active ingredient in SLICE, is a pesticide that is administered to farmed fish through their feed.SLICE has not been:
- tested for food safety by the Canadian Food Inspection Agency
- licensed by Health Canada; or
- permitted for use through the Pesticide Control Act
In B.C., salmon farmers are approved to use SLICE through the Emergency Drug Release Program which allows the use of non-approved drugs when recommended by veterinarians for emergency situations. But SLICE is not used for the occasional emergency. Outbreaks of sea lice are so prevalent in industrial net-pens that the use of SLICE has become standard operating procedure. A steady dependence on SLICE by the B.C. salmon farming industry has been recorded by the Ministry of Agriculture and Lands.
Emamectin benzoate belongs to a class of chemicals called avermectins, which are axonic poisons affecting nerve cells. Farmed fish ingest SLICE as a coating on commercial food pellets. Digestion releases the drug to pass through the lining of the fish’s gut and into the fish’s tissues, from where it takes about a week to be eliminated. Although SLICE contains emamectin benzoate (0.2%), an active ingredient in pesticides, it is classified as a drug because it is fed to the fish rather than applied externally.
Overuse or over-reliance on any single compound has been shown to lead to the development of resistance by the target organism. Evidence of resistance to SLICE has recently been reported in Chile.
SLICE lacks specificity; it puts marine organisms in the vicinity of treated salmon farms at risk. The Salmon Aquaculture Dialogue's report on chemical use notes that sea lice therapeutants (such as SLICE) negatively impact the environment through their effects on sensitive non-target organisms, and may alter nearby wildlife.
