Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on July 20, 2009). Includes bibliographical references.

In this study, microsatellite and mtDNA markers were successfully used to study the population structure of <i>C. carcharias.  </i>Development of new microsatellite loci and the largest sample panel so far assembled for population genetic analyses has given the highest resolution of white shark population structure to-date.  Concordance of direct (photographic identification) and indirect (molecular tools) methods of individual identification was assessed to validate proposed white shark local movements.  The utility of DNA from alternative sources to standard muscle biopsies was tested, with encouraging results obtained from attempts to extract sufficient genomic DNA from white shark teeth.  Female mating strategies were investigated and set in the context of a global phylogeographic study of the white shark, utilizing 304 individuals caught worldwide.  For the first time female promiscuity was documented in two species of Lamniformes, conforming to the typical mating pattern of elasmobranches studied to date.  Finally, the presence of two matrilineal clades in the Atlantic-western Indian and Pacific oceans was revealed, with a deeper substructure within oceans detected by nuclear and mtDNA markers, supporting the hypothesis of female philopatry with gene flow mediated by both sexes.  These findings are essential to the management of white shark populations, a species that has already been classified as ‘Vulnerable’ by the IUCN.

Thesis (M. Sc. (Zoology))--University of Pretoria, 2003. / Includes bibliographical references (leaves 140-153).

Recent research confirmed white shark (Carcharodon carcharias) nursery habitat off Long Island, New York; however, additional research is required to determine the habitat use and fine-scale movements of young-of-the-year and juvenile white sharks within this nursery. Between 2016 and 2019, twenty-five white sharks were fitted with satellite and acoustic tags to better define habitat use. Individuals exhibited horizontal movements parallel to Long Island’s southern shoreline and coastal New Jersey. Log-likelihood chi-square analyses determined preference for water column depth, SSTs, sea surface salinities, and chlorophyll a concentration. Vertical analysis of diving behavior revealed swimming behavior primarily in the upper 20 m of the water column, in temperatures between 18°C and 20°C. Generalized additive mixed modeling suggested SSTs above 20.5°C affected dive depth. These results can help improve characterization of essential fish habitat for young white sharks and provide data to determine the species’ susceptibility to anthropogenic activities. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

The aim of this study was to investigate various aspects of the life history of white sharks Carcharodon carcharias at Dyer Island, South Africa, between August 1999 and January 2001. Inter-specific predatory interactions between the white shark and various potential prey species such as the Cape fur seal (Arctocephalus pusillus pusillus), African penguin (Spheniscus demersus), Cape cormorant (Phalacrocorax capensis), bank cormorant (P. neglectus), crown cormorant (P. coronatus) and white-breasted cormorant. (P. carbo) were observed. White sharks were attracted daily to a research vessel positioned at various anchorages in the vicinity of Dyer Island. Spatial and temporal abundance, and population composition of white sharks were recorded throughout the year and revealed seasonal trends in habitat utilisation. White sharks occupied inshore waters, away from the Geyser Rock seal colony in the summer. Sharks became abundant in the near vicinity of Geyser Rock in the winter period. The summer inshore population was characterised by the increased total length of sharks and the exclusive presence of female sharks. Prey resembling decoys were used to investigate trends in the 'predatory motivation' of white sharks in relation to various independent variables. White sharks displayed greatest predatory motivation in close proximity to a seal colony, in overcast conditions, and when water clarity was low. White sharks evidently elevate their motivation to hunt large prey, which are difficult to catch, in situations where the likelihood of encountering valued prey and completing a successful attack is greatest. Ontogenetic difference in predatory motivation towards the decoys existed, with sharks above 325 cm TL displaying greater predatory motivation than smaller sharks. Various choice tests were conducted to determine the visual discriminatory ability and prey preference of white sharks at Dyer Island. The results suggested that white sharks preferred a biologically familiar shape (pinniped) over an inanimate shape (rectangle), smaller (75 mm TL pinniped) over larger (1800 mm TL pinniped) prey, and a pinniped decoy over a penguin decoy of similar size. Selectivity in larger white sharks (>375 cm TL) was most noticeable in the prey shape (pinniped vs. rectangle) experiment, which suggests they may readily utilise a speculative hunting strategy based on rough similarities between detected potential prey and recognised prey. In this situation mistaken identification of prey is more possible. Smaller white sharks (a majority of the sample) displayed most selectivity in the prey size experiment, with strong preference for the smaller seal decoy over the large one. This pattern indicates that prey size may be a partial limiting factor in the feeding of smaller white sharks. Negative impacts (such as conditioning or distraction) of cage-diving on white sharks were assessed by the measurement of white shark contact time and visit time in relation to the chumming vessel. These results revealed that smaller sharks had longest visit times, and that sharks in the vicinity of Geyser Rock displayed visitation patterns indicative of hunting sharks. Particular vigilance should be kept by operators not to allow small sharks to take bait (reward). The channel area appears to be an important hunting ground and white shark cage-diving should perhaps be restricted in this area. White sharks also showed greater activity around the chumming vessel on cloudy days and operators must be particularly vigilant to deny sharks any rewards (bait) under these conditions. Both the white sharks and Cape fur seals predate and/or attack seabirds and predatory interactions were quantified and qualified by the routine collection and inspection of seabird carcasses and injured birds, as well as opportunistic observations of live attacks throughout this study. White sharks are infrequent predators of seabirds in this ecosystem, perhaps due to an abundance of Cape fur seals (a preferred prey), anti¬predator behaviour by penguins, and seabirds not being a sought after prey type. Cape fur seals were a more conspicuous seabird predator, annually attacking a significant percentage of the adult penguin (1.99-2.52%), white-breasted cormorant (5.21-5.72%), and crowned cormorant (3.13%) populations. A minimum estimate of 1.09% of the fledgling Cape cormorant population also succumbed to Cape fur seal predation. / Dissertation (MSc(Zoology))--University of Pretoria, 2006. / Zoology and Entomology / unrestricted

Mossel Bay is internationally recognised as one of the centres of abundance of white sharks in South Africa. During 2008 – 2010 there were four sites within the bay i.e. Seal Island, Hartenbos, Kleinbrak and Grootbrak, which were sampled to gain insight into the population dynamics of this species. Currently, life history information on white sharks in this area is limited. This study used a combination of mark-recapture using photographic identification techniques and sight per unit effort methods. Inter-annual, seasonal and spatial patterns in abundance are assessed. The effects of environmental parameters on abundance are also investigated. Photographic identification techniques were employed to identify unique individuals within the sampled population. This modified mark-recapture approach is therefore non-invasive and cost-effective. Open population POPAN parameterization was used to analyse the data in software program MARK. The total population was estimated at 389 sharks (351 – 428; 95 percent CI). Over the three year period, a marginal (yet non-significant) decline in numbers was observed, in terms of both monthly and seasonal population estimates. Sightings per unit effort data were collected during sampling trips. The relative abundance and body size composition of white sharks demonstrated significant spatial and seasonal variation. The highest and lowest relative abundance was observed at Seal Island and Hartenbos, respectively, and is likely attributed to prey availability. Although white sharks were present year-round in Mossel Bay, the highest relative abundance occurred during summer and the lowest relative abundance occurred during spring. White sharks were grouped into three main size classes based on estimated total length (TL): Young of the year (YOY) (125 – 174cm), juvenile (175 – 324cm) and adult (325 – 524cm). YOY white sharks were most prevalent at Grootbrak, with juvenile and adult individuals concentrating at Seal Island. Although most size classes were present throughout the year, seasonal differences were observed. YOY individuals were most abundant in the autumn months, juvenile size-classes appeared to concentrate in the study area during winter, and the adult individuals were most abundant in the spring months. Overall, there was a high concentration of white sharks ranging in size between 175 – 324cm TL, and it was thus hypothesised that Mossel Bay represents an interim nursery or grow out area for white sharks in South Africa. Data collected from 2008 and 2009 was used to investigate the relationship between specific environmental parameters, i.e. sea surface temperature and vertical water clarity, in relation to the relative abundance of white sharks. Sea surface temperature and vertical water clarity observed in this study ranged from 9.3 - 22.7°C and 0 – 10m, respectively. Sea surface temperature did not have a significant influence on the relative abundance of white sharks and this may be attributed to the thermoregulatory capacity of the species. Vertical water clarity, however, did significantly influence the relative abundance. Furthermore, the combined effect of site and season significantly influenced the relative abundance of white sharks and is probably linked to the distribution and abundance of inshore prey resources.

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. / Dissertation (MSc)--University of Pretoria, 2012. / Zoology and Entomology / MSc / Unrestricted

The south coast of South Africa represents the extreme western end of the range of the Indo-Pacific humpback (Sousa chinensis, plumbea type) and Indo-Pacific bottlenose dolphins (Tursiops aduncus), which are both confirmed to range as far west as False Bay (Jefferson & Karczmarski, 2001; Hammond et al., 2008). Individual ranging behaviour for both species however is not well resolved. Recent genetic analyses suggest that animals currently considered as plumbea type Sousa chinensis (Reeves et al., 2008) may be a separate species, Sousa plumbea (Mendez et al., 2013). In South African waters less than 1000 adult humpback dolphins (Sousa chinensis, plumbea type hereafter “humpback dolphin”) may comprise the entire population (Karczmarski, 1996), while all estimates suggest the bottlenose dolphin (Tursiops aduncus, hereafter “bottlenose dolphins”) population is relatively large, numbering thousands of animals (Cockcroft et al., 1992; Reisinger & Karczmarski, 2010). Both dolphin species are exposed to variable levels of anthropogenic impacts throughout their range including vessel traffic, chemical pollution and habitat degradation associated with coastal development. This thesis describes the results of a study investigating: 1) the environmental and anthropogenic factors which influence the habitat use of humpback and bottlenose dolphins in two adjacent bays on the southern Cape coast, South Africa – Mossel Bay and Vlees Bay; 2) the abundance of humpback dolphins using Mossel Bay and 3) the interaction of these two dolphin species with white sharks, and the influence this has on dolphin group sizes and habitat use in Mossel Bay. Both land-based and boat-based survey platforms were used in this study with land-based data collected during dedicated watch periods at sites in Mossel Bay (n = 6) and Vlees Bay (n = 4) between February 2011 and March 2013, with a focus on humpback and bottlenose dolphins. A surveyor’s theodolite was used at these sites to collect positional data on animals, while behavioural data were collected through direct observation. Boat-based photographic identification surveys were used to collect data on the presence of individual humpback dolphins in Mossel Bay between April 2011 and November 2013. White shark data from Mossel Bay between February 2011 and March 2013 were provided from boat-based chumming surveys for the collection of photo-ID data from the Master’s thesis of Rabi’a Ryklief, based at Oceans Research. Data were analysed using ANOVA’s, Tukey honest significance tests and generalised additive modelling (Wood, 2006) in programme R, while capture histories of humpback dolphins were analysed with RMark (Laake, 2013) using POPAN open population models (Schwarz & Arnason, 1996) and Huggins heterogeneity closed capture models (Huggins, 1989; Chao et al., 1992). Humpback dolphins socialised over sandy beach habitats in both bays, while feeding/foraging occurred over reef systems in Mossel Bay and off fine grained sandy beach habitats in Vlees Bay. Humpback dolphin resting behaviour was observed at a very low frequency and occurred in all of the primary habitat types in Mossel Bay, while in Vlees Bay resting was only observed over reefs. Bottlenose dolphins in both bays preferentially used wave cut rocky platform habitats for feeding/foraging and resting while socialising occurred in the vicinity of estuaries in Mossel Bay and fine grained sandy beach habitats in Vlees Bay. Higher sighting rates were recorded in the control site, Vlees Bay, than in Mossel Bay for both dolphin species. The largest reverse osmosis desalination plant commenced operations in the sheltered corner of Mossel Bay in October 2011 and discharged approximately five million litres (Ml) of effluent per day (between October 2011 and February 2012) and 18 Ml per day in March and April 2012. In Mossel Bay higher sighting rates of humpback dolphins occurred in the period before desalination began while bottlenose dolphin sighting rates were highest after active desalination decreased to once per month (May, 2012). During the period of peak brine discharge in Mossel Bay, sighting rates were highest for both species in Vlees Bay. Even after desalination operations decreased the sighting rate of humpback dolphins remained low. The operation of the desalination plant at full capacity in Mossel Bay may have led to reduced use of this area by both humpback and bottlenose dolphins. Key habitats in Mossel Bay for both dolphin species are shared with great white sharks (Carcharodon carcharias hereafter “white sharks”) and focus around the three estuaries and their associated near-shore reef systems. The presence of predatory white sharks may limit the time dolphins spend in a specific habitat and influence the number of animals within groups, with larger humpback dolphin groups at sites with high shark utilisation. Both dolphin species had lower individual sighting rates during periods when white shark abundance peaked. Large group sizes of humpback dolphins at Seal Island, and of bottlenose dolphins at Hartenbos and Tergniet, combined with increased rates of travelling and decreased resting and socializing suggest that these areas may pose the largest threat to dolphins due to the variety of shark size classes’ present, especially larger sharks. Closed capture models generated within year population estimates ranging from 48 to 97 individual humpback dolphins (2011: 97, 95% CI: 46 – 205; 2012: 48, 28 – 81; 2013: 68, 35 – 131) while open population modelling produced a ‘super-population’ estimate of 116 animals (95% CI: 54 – 247) using Mossel Bay. During the study 67 humpback dolphins were individually identified with 94.3 % of the individuals in good quality photographs distinctively marked. Fewer humpback dolphins may be present on the south-east and southern Cape coast, including between Algoa Bay and Mossel Bay, than initially thought (Karczmarski, 1996), as definite links exist between Algoa Bay and Plettenberg Bay (Smith-Goodwin, 1997), and Plettenberg Bay and Mossel Bay (this study). The Gouritz River mouth (21º 53' E; Ross, 1984) and De Hoop (20º 30' E; Findlay et al., 1992) were previous suggested as the western limit of this species, but within the last 20 years knowledge on the extent of their range has been greatly improved, and range extension of this species may be occurring to the west with animals present as far west as False Bay (18º 48' E; Jefferson & Karczmarski, 2001). Due to the vulnerability of this species and their wide ranging behaviour, conservation plans need to be implemented on a wide scale to ensure protection of these animals from human impacts throughout their range. A concerted effort is required to further establish the population links between the various locations on the southern Cape coast that these animals frequent. / Dissertation (MSc)--University of Pretoria, 2014. / Zoology and Entomology / MSc / Unrestricted

[For the Abstract, please see the PDF files below, namely "front.pdf"] CONTENTS. Chapter 1 Introduction. Chapter 2 Gross and microscopic visceral anatomy of the male Cape fur seal with reference to organ size and growth. Chapter 3 Age determination and growth in the male Cape fur seal: part one, external body. Chapter 4 Age determination and growth in the male Cape fur seal: part two, skull. Chapter 5 Age determination and growth in the male Cape fur seal: part three, baculum. Chapter 6 Suture age as an indicator of physiological age in the male Cape fur seal. Chapter 7 Sexual dimorphism in the adult Cape fur seal: standard body length and skull morphology. Chapter 8 Reproduction in the male Cape fur seal: age at puberty and annual cycle of the testis. Chapter 9 Diet and foraging behaviour of the Cape fur seal. Chapter 10(a) The Impact of the fur seal industry on the distribution and abundance of Cape fur seals. Chapter 10(b) South African Airforce wildlife rescue: Cape fur seal pups washed from Black Rocks, Algoa Bay, during heavy seas, December 1976. Chapter 11(a) Operational interactions between Cape fur seals and fisheries: part one, trawl fishing. Chapter 11(b) Operational interactions between Cape fur seals and fisheries: part two, squid jigging and line fishing. Chapter 11(c) Operational interactions between Cape fur seals and fisheries: part three, entanglement in man-made debris. Chapter 12 Concentrations of heavy metals (Cd, Cu, Pb, Ni & Zn) and organochlorine contaminants (PCBs, DDT, DDE & DDD) in the blubber of Cape fur seals. Chapter 13 Endoparasites of the Cape fur seal. Chapter 14(a) Preliminary investigations of shark predation on Cape fur seals. Chapter 14(b) Aggressive behaviour of an adult male Cape fur seal towards a great white shark Carcharodon carcharias. Chapter 15 Conclusions and future directions.