Research Document 2021/061
Evaluation of Existing Risk Assessment Methods for Granting Ballast Water Management Exemptions
By Ogilvie, D., Daigle, R., Chassé, J., and Bailey, S.A.
Abstract
The International Maritime Organization’s (IMO) Ballast Water Management Convention permits nations to grant exemptions from specific ballast water management requirements to ships travelling or exclusively operating between specified ports. Furthermore, exemptions must be granted based on scientifically robust risk assessments that indicate a ship’s ballast water activities have a low probability of damaging public health, environment, resources, or property of any nation.
Two existing risk assessment methods — i) Joint Harmonized Procedure and ii) Same Risk Area — that satisfy the requirements of the IMO’s Guidelines for Risk Assessment were assessed by conducting a literature review and applying these methods to case studies in Canada.
The Joint Harmonized Procedure uses detailed port survey data and a decision tree to evaluate risk based on the salinity difference between source and recipient ports and the presence of species of concern. The Joint Harmonized Procedure was applied to a case study where ballast water was transported from Boston, MA, to Saint John, NB. The outcome of the risk assessment was high risk due to the occurrence of seven species of concern and the overlap in salinity between Boston and Saint John. Overall, conducting port surveys to identify harmful species that could be transported from the source to recipient port in ballast water is logical and straightforward, and the decision tree can be adapted to assess factors relevant for predicting survival associated with a given shipping route; e.g. evaluating temperature and salinity tolerances of species of concern against environmental conditions in the recipient port.
The Same Risk Area approach evaluates whether species of concern can disperse unassisted from the source to recipient ports, regardless of their transport in ballast water. To evaluate this method, the natural connectivity between 12 ports in the province of Québec was examined using a trait based biophysical model, assessing various combinations of planktonic duration, swimming behavior, and spawning period. Port connectivity varied greatly between these ports across the trait combinations examined, with some ports having relatively higher connectivity, though most ports had lower or no connectivity. In summary, the Same Risk Area approach is flexible to assess specific species of concern or general character traits when species distribution data are or are not unavailable, respectively. However, port connectivity thresholds (high vs. low) are not well defined, making it difficult to evaluate port connectivity relative to the likelihood of spreading harmful species to the recipient port via ballast water.
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