Influence of Vessel Transit Patterns on Developing a Ballast Water Treatment Strategy for Exotic Species

The accelerating rate of dispersion of exotic aquatic species on a global scale has prompted a need to develop methods to treat ballast water. Vessel transits patterns were assessed to determine the influence of this variable on the development of a ballast water management strategy. Analyses of data sets from four North American ports that included 464 to 2537 different vessels that made 2076 to 8056 visits from overseas to each port over a 3 to 9 years interval indicated two consistent trends. The most important was 45–71% of the vessels visited a port once over the period monitored. Also, less than 20% of the vessels visited a port regularly on an annual basis. The low frequency of visits by individual vessels could influence the design and application of ballast water treatment options.