Movement patterns of coastal dolphins in the presence of a fast-flowing prevailing current: shore-based observations at Cape Vidal, South Africa

Theoni Photopoulou, Peter B Best, Philip Steven Hammond, Ken Findlay

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

The presence and movement of Indo-Pacific bottlenose dolphins Tursiops aduncus were investigated using shore-based observations made during a humpback whale Megaptera novaeangliae migration survey at Cape Vidal, South Africa, undertaken between June and October 1988–1991. Occurrence was analysed as counts of dolphin sightings per hour within a generalised estimating equation framework. Bottlenose dolphin sightings decreased throughout the daily survey period, and there was a small seasonal peak in sightings during August. Data on movement trajectory were collected using a theodolite for 60% of the groups of dolphins sighted. Most groups were observed travelling in a northerly direction, with few groups recorded moving south. A generalised linear model indicated that northward-travelling dolphins were located closer to shore, travelled at higher speeds, and occurred in bigger groups under low-tide conditions, than those seen moving in a southerly direction. The southward-flowing Agulhas Current is close to shore at Cape Vidal, where the continental shelf is particularly narrow. We suggest that bottlenose dolphins in this area have adopted a specific movement regime to cope with the consistent fast-flowing currents that dominate their environment at Cape Vidal.
Original languageEnglish
Pages (from-to)393-401
JournalAfrican Journal of Marine Science
Volume33
Issue number3
DOIs
Publication statusPublished - 11 Jan 2012

Keywords

  • Agulhas Current
  • Generlised estimating equation
  • Generalised linear model
  • Sightings
  • Theodolite
  • Tursiops aduncus

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