Science Advisory Report  2013/064

Science Advice from the National Risk Assessment for Ballast Water Introductions of Aquatic Nonindigenous Species to Canada

Summary

• Ballast water is a vector that poses a significant risk for primary and secondary introductions of aquatic nonindigenous species (NIS) to all regions. A proportion of these NIS is or may become invasive. Invasive species can cause economic, social, or ecological impacts.
• The following Science Advisory Report (SAR) is based on a comparative analysis of the relative risk among 11 ballast water pathways in Canada across Atlantic, Pacific, Arctic and Great Lakes regions (Figure 1). 
• The comparative analysis considers the potential for arrival and survival of zooplankton and phytoplankton NIS (microbes are not considered) in determining introduction potential as well as the magnitude of consequences of these aquatic NIS. The relative risk posed by the discharge of ballast water from commercial ships in Canadian waters was assessed under current ballast water regulatory requirements, as well as future requirements for International Maritime Organization (IMO) D-2 performance standards. 
• The invasion risk currently posed by International Transoceanic vessels arriving to the Great Lakes and St. Lawrence River (GLSLR) was used as the lowest risk benchmark in this study, since ballast water exchange (BWE) is thought to be particularly effective for this pathway and no ballast-mediated NIS have been reported from the Great Lakes since 2006. However, as this is a relative risk assessment, it should be noted that even the lowest ranked pathways pose a risk of invasion.
• Although few ballast water discharges occur in the Arctic, resulting in a relatively low annual risk, the risk posed by individual discharges of International Transoceanic vessels in the Arctic is comparatively high. This risk will increase in the future with expected growth of commercial shipping activities due to longer ice free seasons and northern development. Arctic ports are unlikely to serve as a source of NIS for other Canadian waters.
• Ships operating within the Ballast Water Exemption Zones in the Pacific and Atlantic regions currently pose a relatively high invasion risk. International Exempt vessels are an important pathway for the introduction of zooplankton and phytoplankton NIS into Canadian waters through the transport of un-exchanged ballast water.
• The risk of domestic vessels for introduction of aquatic NIS is variable across regions, taxa and timescales. Lakers pose a relatively high risk for zooplankton NIS at both timescales, while Eastern Coastal Domestic vessels pose a relatively high risk for both zooplankton and phytoplankton NIS on an individual discharge basis. The risk posed by domestic ships in the Arctic is relatively low, while Pacific Coastal Domestic vessels were not assessed due to lack of data.
• While current regulatory requirements for BWE by transoceanic vessels reduce the risk of invasions to freshwater ecosystems (e.g., Great Lakes), these regulations are less effective in reducing the risk to marine ecosystems (i.e., Atlantic and Pacific International Transoceanic pathways are relatively high risk in this assessment).
• The abundance (i.e., number of individuals) of zooplankton NIS would be reduced for all pathways if managed in accordance with the IMO D-2 standard. However, the abundance of phytoplankton NIS would be reduced only for half of the pathways.
• Effective management of all ship-mediated NIS introductions will require consideration of other shipping vectors such as hull biofouling and ballast sediments, by both commercial and non-commercial vessels.  

This Science Advisory Report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, national advisory meeting of March 25-27, and June 19-21 2013 on the National Risk Assessment for ship-mediated introductions of aquatic nonindigenous species to Canada. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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