Introduction Of Chemicals into the Marine Environment
Industrial production of farmed salmon inevitably leads to disease and parasite outbreaks, leading the farm operators to treat their fish with a variety of chemical substances in the form of antibiotics and pesticides. The widespread use of chemicals raises a range of concerns.
In 2003, 37 million farmed salmon in Canada were treated with emamectin benzoate (trade name SLICETM), a parasiticide treatment used to combat sea lice. SLICE is only authorized for use in the marine environment on an “emergency” basis, but outbreaks of sea lice are so prevalent in industrial open net-cages that the emergency” use of SLICE has become standard operating procedure.
SLICE is mixed with feed pellets, but not all the feed pellets are eaten by the farmed fish, and uneaten food will drift down and potentially be eaten by other, wild, marine organisms, some of which are eventually harvested for human consumption. SLICE is also excreted from the fish feces into the marine environment
Of note to consumers interested in what they're eating is the fact that fish treated with SLICE must undergo a withdrawal period before harvesting to ensure fish are drug free.
Antibiotic treatment is also on a steady increase in the farmed salmon industry. The widespread use and introduction of antibiotics into the marine environment may contribute to antibiotic resistance. According to Health Canada, antibiotic resistance is an emerging global health issue that may become one of the most significant public health challenges worldwide.
Chemicals used to streamline fish farming operations also pose a threat. To prevent the growth of seaweed, barnacles and mussels on the nets used in open net-cage fish farms, most nets are painted with a toxic coating. As densely crowded farm salmon competitively gulp food pellets tossed into the water, they may ingest the toxic paint flakes drifting from all sides of the pen.
Chemicals used in salmon farming have also been found to kill the life in the sediments underneath salmon farms (see Pollution Concerns).
