Browsing by Author "Towner, Alison"

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    Great white sharks Carcharodon carcharias in Gansbaai, South Africa : environmental influences and changes over time, 2007-2011
    (2012) Towner, Alison; Underhill, Les; Smale, Malcolm
    The South African Government introduced protective legislation prohibiting targeted fishing of the great white shark Carcharodon carcharias in 1991. This pre-emptive measure was intended to protect this species from increasing fishing pressure to allow researchers to gather information of this shark’s distribution, basic life history traits, breeding behaviour, and habitat use. Following this, the species conservation status was placed on CITES Appendix II and classified on the IUCN (International Union for the Conservation of Nature) Red List as Vulnerable. This thesis investigates white sharks at Gansbaai, in particular their occurrence, changes over time and the influence of environmental variables on their numbers there. The size and numbers of white sharks were recorded from an anchored cage diving vessel over a five-year period between 2007 and 2011. The study was conducted around Dyer Island and the inshore region of Gansbaai in the Western Cape of South Africa. A change in size frequency between seasons suggests that the white sharks are not resident for long periods, but that different size classes use the coastal bay at different times. There was a statistically significant change of size distribution over the five years for both male and female sharks. The trend of larger sizes recorded later in the study could infer a change in the cohorts visiting the bay or growth of the same individuals exhibiting site fidelity to the area.