Seasonal fluctuations in occurrence of inshore Bryde’s whales in Plettenberg Bay, South Africa, with notes on feeding and multispecies associations

  • GS Penry
  • VG Cockcroft
  • PS Hammond

Abstract

Seasonal fluctuations in the occurrence of inshore South African Bryde’s whales Balaenoptera edeni were investigated between November 2005 and June 2008. Sighting data were collected in Plettenberg Bay on the south-east coast of South Africa. Bryde’s whale occurrence was modelled in relation to the following environmental covariates: sea surface temperature, chlorophyll a concentrations and wind speed. Seasonal increases in encounter rates (sightings per day) were observed during summer and autumn, with a peak in April that corresponded to increased feeding activity and above average aggregation sizes. All three environmental covariates were significant factors in terms of explaining variability in the occurrence of whales. Multispecies associations with common dolphins Delphinus capensis and Cape gannets Morus capensis were most common in summer and autumn, when feeding activity was highest.

Keywords: Balaenoptera edeni, chlorophyll a, generalised linear models, multispecies associations, seasonality, SST

African Journal of Marine Science 2011, 33(3): 403–414

Author Biographies

GS Penry
Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, Fife KY16 8LB, Scotland, UK; Centre for Dolphin Studies, Department of Zoology, PO Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031, South Africa; Mammal Research Institute, University of Pretoria, c/o Iziko South African Museum, PO Box 61, Cape Town 8000, South Africa
VG Cockcroft
Centre for Dolphin Studies, Department of Zoology, PO Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031, South Africa
PS Hammond
Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, Fife KY16 8LB, Scotland, UK
Section
Articles

Journal Identifiers


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