Research Document - 2011/105

Risk Assessment for ship-mediated introductions of aquatic nonindigenous species to the Canadian Arctic

By F.T. Chan, J.E. Bronnenhuber, J.N. Bradie, K.L. Howland, N. Simard, and S.A. Bailey

Abstract

Ballast water has historically been the predominant ship-mediated vector for aquatic non-indigenous species (NIS) introductions to Canada, while hull fouling is recognized as a leading sub-vector for the introduction of marine aquatic NIS worldwide. To the best of our knowledge, there has been no ship-mediated NIS established in the Canadian Arctic. However, if shipping activities increase as expected with a warming climate, propagule pressure will also increase and the Arctic will be more vulnerable to future invasions. The objective of this report was to conduct a relative risk assessment of shipping vectors (hull fouling and ballast water) to Canadian Arctic ports. First, the probability of introduction was estimated by combining the individual probabilities of successful transition through each stage of the invasion process (i.e., arrival, survival and establishment), based on ship arrival/ballast water discharge data and environmental conditions at Arctic and potential source ports. Second, the potential magnitude of consequences of introduction was estimated based on the number of high impact ship-mediated NIS recorded for eco-regions of ports directly connected to Arctic ports through shipping activities. The probability of introduction and potential magnitude of consequences were then combined for a final relative invasion risk rating. Finally, we identify priorities and make recommendations for future management needs.

A transit analysis shows that Canadian Arctic ports are connected with international and coastal domestic ports, resulting in potential for species transfers via hull fouling and ballast water discharge. The final relative invasion risk for fouling NIS is higher for Churchill (Manitoba), intermediate for Iqaluit and Erebus Bay/Beechey Island (Nunavut) and lower for other Arctic ports, with moderate uncertainty. The final relative invasion risk for ballast-mediated NIS is higher for Churchill and lower for all other ports, with moderate uncertainty. It is important to note that results presented in this document are based on relative rankings among top Arctic ports. Ports identified as higher risk in this study may not be high risk in a national scale considering the relatively low shipping traffic and harsh environmental conditions in the Arctic; these ratings will be recalibrated to differentiate risk among top ports from all Canadian regions in a subsequent national risk assessment.

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