1. Marine and Coastal Management, Private Bag X2, Rogge Bay, Cape Town 8012, South Africa
2. Marine Biological Research lnstitute, Zoology Department, University of Cape Town, Rondebosch, Cape Town 7701, South Africa
3. School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa