Residency, habitat use and sexual segregation of white sharks, Carcharodon carcharias in False Bay, South Africa

PLoS One. 2013;8(1):e55048. doi: 10.1371/journal.pone.0055048. Epub 2013 Jan 28.

Abstract

White sharks (Carcharodon carcharias) are threatened apex predators and identification of their critical habitats and how these are used are essential to ensuring improved local and ultimately global white shark protection. In this study we investigated habitat use by white sharks in False Bay, South Africa, using acoustic telemetry. 56 sharks (39 female, 17 male), ranging in size from 1.7-5 m TL, were tagged with acoustic transmitters and monitored on an array of 30 receivers for 975 days. To investigate the effects of season, sex and size on habitat use we used a generalized linear mixed effects model. Tagged sharks were detected in the Bay in all months and across all years, but their use of the Bay varied significantly with the season and the sex of the shark. In autumn and winter males and females aggregated around the Cape fur seal colony at Seal Island, where they fed predominantly on young of the year seals. In spring and summer there was marked sexual segregation, with females frequenting the Inshore areas and males seldom being detected. The shift from the Island in autumn and winter to the Inshore region in spring and summer by females mirrors the seasonal peak in abundance of juvenile seals and of migratory teleost and elasmobranch species respectively. This study provides the first evidence of sexual segregation at a fine spatial scale and demonstrates that sexual segregation in white sharks is not restricted to adults, but is apparent for juveniles and sub-adults too. Overall, the results confirm False Bay as a critical area for white shark conservation as both sexes, across a range of sizes, frequent the Bay on an annual basis. The finding that female sharks aggregate in the Inshore regions when recreational use peaks highlights the need for ongoing shark-human conflict mitigation strategies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acoustics
  • Animals
  • Bays*
  • Behavior, Animal*
  • Body Size
  • Ecosystem*
  • Female
  • Male
  • Seasons
  • Sex Factors
  • Sharks* / growth & development
  • South Africa
  • Telemetry

Grants and funding

Bursary funding for AAK was provided for her MSc research from the National Research Foundation and for her PhD research through a grant to CG from the National Research Foundation (South Africa) (http://www.nrf.ac.za) SEAChange Programme. The Department of Environmental Affairs provided additional research equipment and ship time. The Save Our Seas Foundation provided a grant to AAK to conduct this research. The funders had no role in study design, analysis and decision to publish. MM and DK (employees of the Department of Environmental Affairs who supplied research equipment and ship time) assisted in collection of the data and contribution of materials. Both also reviewed the manuscript before publication.