Chemicals and Additives
New Zealand salmon farms use diets especially prepared for king salmon. These diets do not contain antibiotics, vaccines, steroids or other growth enhancers.
The feed contains zinc (concentrations of ~130 - 150 mg/kg), which is an essential micronutrient for the prevention of cataract formation and other health problems. Zinc can accumulate in sediments beneath fish farms and can be toxic in high concentrations. Feed companies are presently working to minimise zinc discharges to the seabed, mainly by reducing the content in the feed.
Copper can also accumulate in sediments below farms and, like zinc, can also be toxic in high concentrations. Copper comes from antifouling paint, used to reduce build-up of fouling organisms. New Zealand salmon farming companies actively minimise the use of copper antifoulant paints and use manual defouling as much as possible. Research is ongoing into other antifouling treatments as alternatives to copper-based paints.
The relative absence of salmon diseases and parasites in New Zealand waters means chemical treatments against these things are not used in New Zealand salmon farms.
Other chemical contaminants such as dioxins, polychlorinated biphenyls (PCBs) and heavy metals like mercury, are globally ubiquitous compounds that accumulate in animal tissue (including humans) via the food chain.
In New Zealand, PCB and dioxin levels in sea-cage salmon are well within health guidelines stipulated by various regulatory agencies, and as such are unlikely to be a risk to the wider ecosystem or to consumers’ health.
The New Zealand salmon industry and feed supply companies implement various measures to minimise contaminant inputs to the environment, which will likely lead to reduced contaminant loads in the future.
