Agriculture and Environment: Salmon
Environmental Impacts of Production: Use of Antifoulants
While the net cages can vary considerably by area, they tend to be some 20 metres deep. One of the main problems that the net cages pose is the potential for fouling.
Shellfish and marine algae grow on the nets and can make them extremely heavy. This makes the lifting and cleaning of the nets very difficult, and it shortens the lifetime of the investment (Ellis and Associates 1996).
To avoid fouling and to prolong the life of the cage, growers often use antifouling paints. Such paints, by definition, are highly toxic given that that is how they prevent organisms from growing on painted structures. The most commonly use antifoulants (organotin or copper-based compounds) are toxic to bivalves and could be harmful to fish species as well (Cripps and Kumar 2003).
Titanium, copper, and tributylin (TBT) have been used in marine paints, and are known to be harmful to shellfish. However, some of these paints are also known to accumulate in the tissues of fatty fish such as salmon and are therefore inappropriate for use around fish intended for human consumption.Tributylin has been shown to be highly toxic to marine life, causing reproductive failure and growth abnormalities in molluscs. In addition, paints containing oxytetracycline should be prohibited from salmon aquaculture operations because they are known to result in increased antibiotic resistance (Ellis and Associates 1996).