Cargo vessel ballast water as a vector for the transport of non-indigenous marine species

Abstract

The fauna in ballast water tanks of bulk cargo vessels sailing between Japan and Australia was investigated over two years. Two fish species ( Therapon jarbua and Ptereleotris sp.) were found. Twenty-two zooplankton species and 45 other planktonic taxa were collected. Of these, six copepod species ( Calanus sinicus, Centropages abdominalis, C. yamadi, Labidocera bipinnata, Pontellopsis tenuicauda and Corycaeus affinis), and one mysid ( Neomysis japonica) are endemic to Japan. In sediments from ballast tanks, 16 species and at least 21 taxa were found. Species endemic to Japan included two amphipods ( Melita rylovae, Orchomene pacifica), one mysid ( Acanthomysis shrencki), two brachyuran crabs ( Pinnixa rathbuni and Pinnaxodes mutsuensis) and one caridian shrimp ( Alpheus hoplocheles). The number of planktonic species and taxa arriving in Australia in ballast water tanks tended to decrease with increased voyage time. Mid-ocean exchange of ballast water en route greatly reduced the number of planktonic species. We estimated that two-thirds of the taxa that could be expected to be found have so far been recorded. These results suggest that water and sediment carried in ballast tanks of bulk cargo ships can act as an important inter-continental vector for the spread of planktonic and benthic species.