Overview of the aquaculture Pathways of Effects tool for assessing aquaculture impacts

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A Pathways of Effects (PoE) model is a tool that conveys complex interactions between human activities, the type of cause-effect relationships that are known to exist, and the mechanisms by which stressors ultimately lead to effects in the aquatic environment. The model recognizes that a single environmental stressor can have multiple source activities and can lead to one or more environmental effects. It also recognizes that a single environmental effect can be influenced by one or more stressors or activities. In considering a specific activity, it is important that site specific attributes and anticipated ecosystem changes (in addition to specific aquaculture stressors), like climate change, be incorporated into the assessment of effects and the evaluation of the efficacy of potential mitigation measures.

Fisheries and Oceans (DFO) Fisheries Protection Program (FPP) uses Pathways of Effects models in evaluating projects. Consistent with this approach, fish and fish habitat impact evaluation of new aquaculture sites by DFO consider the range of activities, associated stressors and the effects of these stressors on different components of the ecosystem.

In making decisions around aquaculture activities, following the Framework for Aquaculture Risk Management (FARM), the Aquaculture Pathways of Effects are used to identify issues for scientific assessment and advice, and support the risk management steps of identifying mitigation options, the selection of risk management strategies and the determination of the residual risk after the application of mitigation measures.

Aquaculture Pathways of Effects

The Aquaculture Pathways of Effects model (Figure 1) was developed collaboratively with Provincial and Territorial regulators. A Canadian Science Advisory Secretariat (CSAS) process confirmed the scientific basis for the linkages between the following major stressor categories associated with aquaculture activities, the resulting stressors that can result, and the potential effects of these stressors on different ecosystem and environmental componentsFootnote 1.

As additional data from monitoring around aquaculture sites and new scientific research results becomes available, the characterization of the duration, scale and intensity of the stressor-effects relationships will need to be reviewed and updated to reflect this new information.

Graph: Pathways of Effects for finfish and shellfish aquaculture.
Figure 1: Pathways of Effects for Finfish and Shellfish Aquaculture
Long description

Pathways of effects for finfish and shellfish aquaculture.

Activities include placement/removal of infrastructure, use of industrial equipment and site and stock management.

Stressors include physical alteration of habitat, alteration of light, noise, release of chemicals and debris, release/removal of nutrients, release/removal of fish and release of pathogens.

Effects include change in suspended sediment concentration, water flow, containment concentration, habitat structure/cover/vegetation, primary productivity, oxygen, access to habitat/migration routes, substrate composition/geochemistry, food availability/supply, wild fish populations/communities and wild fish and/or farmed fish health.

At the point of evaluating a specific aquaculture application, the linkages between each of the stressors and the relevant effects described in the Aquaculture Pathways of Effects Tool are considered. The specific environment and activity will determine which stressor-effect linkages exist, and what mitigation measures can be used to effectively and sustainably “break” or lessen the stressor-effect linkages. The residual risks to each of the environmental components from the aquaculture activities following the application of mitigation measures, are then considered in the Risk Management Strategy.

Stressor descriptions

Information and examples of how the Aquaculture Pathways of Effects Tool can be used to support aquaculture decisions within the Framework for Aquaculture Risk Management can be found in the associated document Framework for Aquaculture Risk Management: Application of the Aquaculture Pathways of Effects in Aquaculture Activities Decisions.

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