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Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South Africa
Dissertation (MSc)--University of Pretoria, 2012.
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University of Pretoria
2013
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| _version_ | 1867613676383502336 |
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| access_status_str | Open Access |
| author2 | Bester, Marthan Nieuwoudt |
| author_browse | Bester, Marthan Nieuwoudt |
| author_facet | Bester, Marthan Nieuwoudt |
| collection | Thesis |
| dc_rights_str_mv | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria E13/4/450/ |
| description | Dissertation (MSc)--University of Pretoria, 2012. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/30926 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:39:56.028Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2013 |
| publishDateRange | 2013 |
| publishDateSort | 2013 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/30926 Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South Africa Bester, Marthan Nieuwoudt Jewell, Oliver Joseph David UCTD White shark (Carcharodon carcharias) Movement-based kernel density estimation Conservation hotspots Cape fur seal (Arctocephalus pusillus pusillus) Site specific foraging Dissertation (MSc)--University of Pretoria, 2012. Dyer Island is thought to host one of the most abundant populations of white sharks on the planet; this is often credited to the large (55 – 60,000) Cape fur seal colony at Geyser Rock. Yet relatively little work has ever been produced from the area. This may be attributed to the harshness in its location as a study site, exposed to wind and swell from west to east which limits research periods. This study accounts for over 220 hrs of manual tracking at Dyer Island with a further 68 added from the inshore shallow areas of the bay. Sharks focused their movements and habitat use to reefs or channels that allowed access to Cape fur seals. Movement- Based Kernel Estimates (MKDE) were used to compute home range estimates for shark movements through and around the heterogeneous structures of Dyer Island and Geyser Rock. Inshore two core areas were revealed, one being the major reef system at Joubertsdam and the other at a kelp reef where the tracked shark had fed on a Cape fur seal. At Dyer Island one core area was identified in a narrow channel, ‘Shark Alley’, here a second tracked shark foraged for entire days within meters of rafting Cape fur seals. Rate of Movement (ROM) and Linearity (LI) of tracks were low during daytime and movements were focused around areas such as Shark Alley or other areas close to the seal colony before moving into deeper water or distant reefs with higher rates of ROM and LI at night. If moonlight was strong foraging would take place to the south of Geyser Rock but with higher ROM and LI than observed during the day. Foraging patterns in this study contrast studies from other sites in South Africa and home range and activity areas were comparatively much smaller than observed in Mossel Bay. It has been established that several known white sharks forage at Dyer Island and the other studied aggregation sites, such differences in foraging would suggest that they are able to adapt their foraging behaviour to suit the environment they are in; making them site specific in their foraging ecology. Both satellite and acoustic telemetry are revealing aggregation hotspots of white sharks in South Africa. It is important that such information is used to assist the recovery of the species which has been protected since 1991, yet is rarely considered in planning of coastal developments. Zoology and Entomology MSc Unrestricted 2013-09-09T07:51:46Z 2013-06-28 2013-09-09T07:51:46Z 2013-04-12 2012 2013-06-20 Dissertation Jewell, OJD 2012, Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South Africa, MSc Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/30926> E13/4/450/gm http://hdl.handle.net/2263/30926 http://upetd.up.ac.za/thesis/available/etd-06202013-160414/ © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria E13/4/450/ application/pdf University of Pretoria |
| spellingShingle | UCTD White shark (Carcharodon carcharias) Movement-based kernel density estimation Conservation hotspots Cape fur seal (Arctocephalus pusillus pusillus) Site specific foraging Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South Africa |
| title | Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South Africa |
| title_full | Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South Africa |
| title_fullStr | Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South Africa |
| title_full_unstemmed | Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South Africa |
| title_short | Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South Africa |
| title_sort | foraging ecology of white sharks carcharodon carcharias at dyer island south africa |
| topic | UCTD White shark (Carcharodon carcharias) Movement-based kernel density estimation Conservation hotspots Cape fur seal (Arctocephalus pusillus pusillus) Site specific foraging |
| url | http://hdl.handle.net/2263/30926 http://upetd.up.ac.za/thesis/available/etd-06202013-160414/ |