1. Marine Apex Predator Research Unit, Institute for Coastal and Marine Research, Nelson Mandela University, PO Box 77000, Port Elizabeth 6031, South Africa
2. Southern African Foundation for the Conservation of Coastal Birds, 22 Pentz Drive, Tableview, Cape Town 7441, South Africa
3. Harbor Branch Oceanographic Institute, Florida Atlantic University, 5600 US 1, Fort Pierce, Florida 34946, USA