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Research Document - 2010/017

Pathway of effects of chemical inputs from the aquaculture activities in Canada

By L.E. Burridge, K.G. Doe, and W. Ernst


As in all animal food production systems, it is often necessary to treat aquaculture species for diseases, parasites and fouling organisms. The types of therapeutants available for use and the treatment protocols are tightly regulated in Canada and therapeutants can only be used under prescription from a licensed veterinarian. Management practices have evolved as health threats appear and husbandry has greatly improved over the past 20 years. However, aquaculturists still rely on the use of pesticides and drugs to combat infestations of ectoparasites, antibiotics to treat diseases, metals and products such as lime to combat fouling organisms and disinfectants to ensure biosecurity at aquaculture sites. Chemotherapeutants used in the aquaculture industry are considered either a drug or a pesticide depending on the use and method of application. Health Canada regulates the use of both drugs and pesticides and makes the distinction between them based on the method of application. If the product is applied topically or directly into water, it is considered a pesticide; however, if a product is delivered through medicated feed or by injection, it is considered a drug.

In this report, the types of chemicals used in normal aquaculture practices in Canada are examined for their physical and chemical characteristics, their potential to affect the aquatic environment and species therein and the likelihood that these effects will occur. The main objective of this report is to evaluate the pathway of effects of the various chemical types to identify their stressor-effects such as the presence, effects and consequences in and on non-target aquatic organisms. Each chemical type is assessed for the state of knowledge in relation to stressor-effects, measurable ecological outcomes or endpoints, the magnitude of the effect, the identification of factors and conditions that modify or influence the effect, biological implications, the availability and strength of evidence for the stressor-effect relationship, uncertainties, activities under which stressor-effects occur, and cascading effects or linkages. Pathway of effects diagrams have been created for water borne compounds and in-feed compounds.

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