Marine alien species in Western Cape harbours, South Africa: A tool for stategically focusing monitoring efforts

Master Thesis


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University of Cape Town

Alien species are the second most important cause for the loss in biodiversity globally, after habitat destruction. Marine alien species are transferred across the globe through various vectors, including ballast water, hull fouling, aquaculture facilities and the aquarium and pet trade. Ballast water has previously been considered as the primary vector of alien species transfer. However, fouling is becoming widely recognised as an important vector for the transfer of marine alien species both internationally, as well as in South Africa, where it has been reported to contribute 48% of marine species introductions. The objectives of this study were to document alien species from fouling assemblages in six South African harbours (St Helena Bay, Saldanha Bay, Table Bay, Hout Bay, Gansbaai and Mossel Bay) and to use the data collected to identify factors (such as vectors and other harbour characteristics and activities), that could be used by management authorities to target harbours upon which to focus monitoring efforts. This was done by taking subtidal scrape samples and visual samples from harbour walls and pillars. The prioritisation of harbours was obtained through the use of regression tree models utilising CART (Classification and Regression Trees).

Includes bibliographical references.