Research Document - 2004/118

Ecological and Oceanographic Criteria for Alternate Ballast Water Exchange Zones in the Pacific Region

By Levings, C.D., M.G.G. Foreman

Abstract

We present an overview of the ecological risk associated with draft zoning regulations for disposal of ballast water that has not been exchanged in mid-ocean before vessels arrive at ports in British Columbia. Using data on average seasonal currents off the BC coast, we analysed the possible transport of ballast water organisms into deep ocean habitats and away from key ecosystems and habitats (pilot MPAs, productive fishing grounds, spawning grounds, areas of high primary and secondary productivity, aquaculture operations, areas where ballast water is already being discharged or exchanged, and submarine and estuarine features promoting landward transport). To decrease the risk of possible harm to coastal ecosystems, an amendment of the draft Transport Canada “Annex II” alternate ballast water exchange zone (ABWEZ) is suggested, as given below. Our analysis of currents, bathymetry, and eddies provide rationale for these amendments. Consideration is required of special ABWEZs inshore of the 50 n mi/500 m depth boundary, should weather conditions or other factors require them. Previous assessments showed that an ABWEZ in Juan de Fuca Strait and entrance was associated with risk for non-indigenous species introduction. Further risk assessment is required to investigate the suitability of other special ABWEZs in Pacific region. We also discuss the problematic issue of coastal transport of ballast water organisms and suggest some possible steps to reduce dispersal from this vector into BC waters.

With the exception of Bowie Seamount (53° 19′ 135° 38′, 50  mi (92.6 km) diameter exclusion) and western Queen Charlotte Sound (50 n mi headland (50° 46.5′; 128° 26.0′) to headland (51° 55.6′; 131° 0.0′)), our proposed alternate ballast water exchange zone includes any waters more than 50 nautical miles from the coast and west of the 500 m depth contour.

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