Terms of Reference

Freshwater Cage Aquaculture: Ecosystems Impacts from Dissolved and Particulate Waste Phosphorus

Regional Peer Review – Central and Arctic Region

June 17-19, 2014
Winnipeg, MB

Co-Chairs: Jay Parsons and Corina Busby

Context

Organic waste material from open net pen finfish aquaculture operations in freshwaters is released directly into aquatic environments.  These wastes may be in the form of particulate matter (e.g., uneaten feed and feces) which typically settle to the benthic environment beneath and near the cage arrays, or they may be in the form of dissolved wastes (e.g., carbon, nitrogen, phosphorus released from feed, feces and metabolic excretions of fish) which are released directly into the water column.  Fish size, water temperature and aquaculture practices (e.g., feed composition, ration, and feeding methods) are some of the factors that can affect the level of waste production.  The release of phosphorus in the freshwater environment is of particular concern because it is generally the most limiting nutrient for plant growth in freshwater ecosystems. Excessive inputs of phosphorus into freshwater can lead to increased algal growth and result in decreased oxygen concentrations.

There has been little research into the cycling of phosphorus between aquaculture waste accumulations and the water column and it is not known what proportion of phosphorus released from aquaculture operations is or will eventually be available for primary production. Research at the Experimental Lakes Area was undertaken to determine the ecological consequences of freshwater cage aquaculture by evaluating how phosphorus, nitrogen and carbon from aquaculture facilities cycle in the freshwater environment.

The lack of tested tools for predictive modelling and a thorough understanding of the long term fate of phosphorus released from freshwater aquaculture operations generate apprehension for the public and industry about potential environmental damage and create reliance on a precautionary rather than a science-based approach to regulation of the industry.  A sound scientific understanding of potential effects and scale of phosphorous release from aquaculture operations in freshwater is required if the industry is to grow in an environmentally sustainable fashion.

Based on a review of the current scientific knowledge of the release of phosphorous (dissolved and particulate) from freshwater cage aquaculture operations, this scientific review process will aim to provide advice on the potential impacts that might be associated with phosphorous enrichment by the freshwater cage aquaculture industry.

Objectives

1. Review importance of phosphorus to the freshwater environment and in particular those Canadian ecosystems where cage aquaculture is prevalent.
2. Review what is known of the type and amounts of phosphorus inputs from freshwater cage farms, including a review of estimation methods, and place inputs in context of other natural and anthropogenic sources.
3. Review what is known of cycling and fate of the chemical forms of in the freshwater environment, focussing on those chemical forms of phosphorus that are associated with cage aquaculture activities.
4. Review what is known of methods to predict, manage and mitigate effects of cage aquaculture phosphorus in the freshwater environment.
5. Assess risk of phosphorus inputs from the cage aquaculture industry to Canadian freshwater environments.
6. Identify important knowledge gaps that affect our ability to assess the risk that phosphorus release from the cage aquaculture industry poses to freshwater environments.

Expected Publications

• Science Advisory Report
• Proceedings
• Research Document

Participation

• Fisheries and Oceans Canada (DFO) (Ecosystems and Oceans Science, and Ecosystems and Fisheries Management sectors)
• Environment Canada
• Ontario Ministry of the Environment
• Academia
• Aquaculture Industry
• Other invited experts