Reproductive phenology of the introduced kelp Undaria pinnatifida (Phaeophyceae, Laminariales) in Port Phillip Bay(Victoria, Australia)

摘要

A thorough understanding of the repro-ductive phenology of introduced species is crucial foreffective management and control. Undaria pinnati-fida is an invasive macroalga from the NorthwestPacific which has been recently introduced into threecountries in the Southern Hemisphere: Australia,New Zealand and Argentina. Reproductive pheno-logical studies in Port Phillip Bay, Australia, wereundertaken and compared with other populations inthe Southern Hemisphere, especially with those fromTasmania which were suspected to be very different.The growth season began earlier in Port Phillip Baythan in Tasmanian populations, and abundance washigher. Growth rates were lower in Port Phillip Bay,but this might be due to the different morphology ofboth populations. The maximum spore release com-petency of U. pinnatifida in Port Phillip Bay was12.1 x 10~5spores cm~(-2)h~(-1)which is 20 times themaximum obtained in Tasmania (0.6 x 10~5sporescm~(-2)h~(-1)). For most of the growth season, sporerelease competency ranged between 2 and 3 x 10~5spores cm~(-2)h~(-1), 3-5 times more than in Tasmania.Undaria pinnatifida has not been established outsidePort Phillip Bay in continental Australia, but a precautionary approach should be undertaken inorder to avoid further spread. Monitoring for earlydetection and removal of immature sporophytes priorto spore release seem to be the best options. Thismonitoring should be continuous since new recruitsmay appear throughout the growth season (April—February) and it should be combined with informa-tive programmes to reduce the chances of spread.