Research Document - 1999/211

Review of current practices to reduce the risk of introducing non-indigenous species into Pacific region via ballast water.

By C.D. Levings

Abstract

The contemporary solution used to minimize the risk of moving NIS (non-indigenous species) around the world oceans in ballast water is mid-ocean exchange. In this procedure, if safety permits, the majority of the coastal water in a ship's ballast tanks is replaced with water from mid-ocean, containing organisms not adapted to coastal conditions, so that when a vessel arrives in an overseas port, the ballast water pumped into a harbour contains organisms that should not survive. Estimates of the efficiency of mid-ocean exchange vary widely, and are usually considerably less than 100 %.

Vancouver Port Authority (VPA) developed the mandatory ballast water program to reduce the risk of NIS arrival into waters under their jurisdiction. This protocol, established in 1997 under the VPA Harbourmaster's Standing Orders, is incorporated in the proposed Canadian national guidelines for ballast water management and has been adopted by port authorities in Fraser Port (New Westminster) and Nanaimo. Briefly, if a ship has not performed mid ocean ballast water exchange, with some exemptions, the vessel can be sent back out to sea to exchange ballast water at an alternate or backup site in Juan de Fuca Strait, subject to safety concerns. Initially the backup site specified was Race Rocks but more recently Sheringham Point is indicated. To date no ships have been sent to an alternate location.

The decision to exempt ships that have taken on ballast water from north of Cape Mendocino in California from the VPA Standing Orders should be re-examined as this enhances the risk of moving NIS from ports in Oregon and the outer Washington coast to Pacific region. Ships with ballast water amounts of <1000 tonnes are also exempted. This should also be re-examined since only a few individuals or spores in the residual water and mud in a tank can establish a NIS population. VPA has a program to determine compliance rate for mid-ocean exchange. If ballast water is found to have salinity of > 25 psu or a preponderance of oceanic copepods (calanoids) over bottom dwelling coastal copepods (harpacticoids), the vessel has complied. An assessment is required to determine the statistical power and biological validity of the sampling program. Other BC ports (eg Prince Rupert, Victoria) should become involved in efforts to reduce the risk of introducing NIS to Pacific region.

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