Recolonisation of the Robberg Peninsula (Plettenberg Bay, South Africa) by Cape fur seals

  • J Huisamen
  • SP Kirkman
  • LH Watson
  • VG Cockcroft
  • PA Pistorius

Abstract

The Cape fur seal Arctocephalus pusillus pusillus colony at Robberg Peninsula, Plettenberg Bay, on the south-east coast of South Africa, was driven to extinction by indiscriminate harvesting by the late 1800s. Seals only began to recolonise this site in the 1990s. This study describes the recolonisation process from 2000 to 2009, exploring both within- and between-year count data of seals using the site. Counts increased over the study period from <300 animals to >3 100. Generalised linear models indicated the importance of year and month in explaining variability in the counts. Withinyear variability in the counts decreased over the study period, which may be related to an increasing proportion of resident (as opposed to transient) seals in the colony. However, the colony is currently still in a transition phase with a low ratio of breeding to non-breeding animals, based on the low numbers of pups born in the colony (currently still <100 per year). The influx of seals to the Robberg area may be  associated with shifts in prey availability at the ecosystem level. The colony benefits from the protection afforded by the reserve status of the Robberg Peninsula and the existence of a marine protected area adjacent to it. However, human interference associated with fishing and/or ecotourism on the peninsula may inhibit development into a substantial breeding colony. Potential interventions for the conservation and management of this colony are discussed.

Keywords: Arctocephalus pusillus pusillus, breeding, counts, marine protected area, population trend

African Journal of Marine Science 2011, 33(3): 453–461

Author Biographies

J Huisamen
School of Natural Resource Management, Nelson Mandela Metropolitan University, Private Bag X6531, George 6530, South Africa; CapeNature, Private Bag X6546, George 6530, South Africa
SP Kirkman
Oceans and Coasts, Department of Environmental Affairs, Private Bag X2, Rogge Bay 8012, South Africa; Animal Demography Unit, Department of Zoology, University of Cape Town, Cape Town 7701, South Africa
LH Watson
School of Natural Resource Management, Nelson Mandela Metropolitan University, Private Bag X6531, George 6530, South Africa
VG Cockcroft
Department of Zoology, Nelson Mandela Metropolitan University, PO Box 7700, Port Elizabeth 6031, South Africa; Centre for Dolphin Studies, PO Box 1856, Plettenberg Bay 6600, South Africa
PA Pistorius
Department of Zoology, Nelson Mandela Metropolitan University, PO Box 7700, Port Elizabeth 6031, South Africa
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X