Thesis (Ph.D.)--University of Rhode Island, 2007. / Includes bibliographical references (leaves 98-129).

Thesis (M.S.)--University of South Florida, 2003. / Title from PDF of title page. Document formatted into pages; contains 89 pages. Includes bibliographical references.

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

Thesis (M. Sc.)--College of William and Mary. / Vita. Includes bibliographical references.

Thesis (M. Sc.)--College of William and Mary. / Vita. Includes bibliographical references (leaves 85-89).

Thesis (M.S.)--North Carolina State University, 2003. / Title from PDF t.p. (viewed on Aug. 21, 2004). Includes vita. Includes bibliographical references (p. 88-94).

Bull sharks (Carcharhinus leucas) are globally distributed top predators that play an important ecological role within coastal marine communities. However, little is known about how the spatial and temporal scales of their habitat use are associated with their ecological role. In this study, a population of sub-adult and adult bull sharks were investigated within a remote subtropical marine community in the southwest Indian Ocean off the coast of southern Mozambique. The main objectives of the study were to test a minimally invasive remote biopsy sampling method; to investigate the feeding ecology of bull sharks; and to investigate the temporal and spatial scales of bull shark residency patterns and migration dynamics. Biopsy tests on free-swimming bull sharks showed that the devised sampling technique provided a minimally invasive and consistent method (biopsy retention rate = 87%) to obtain muscle tissue samples sufficiently large enough (310±78mg, mean ± SD) for stable isotope analysis. Results from the stable isotope analysis showed that adult bull sharks appeared to exhibit a shift towards consistentlyhigher trophic level prey from an expanded foraging range compared to sub-adults, possibly due to increased mobility linked with size. Additionally, bull sharks had significantly broader niche widths compared to top predatory teleost assemblages with a wide and enriched range of δ13C values relative to the local marine community, suggesting that they forage over broad spatial scales along the east coast of southern Africa. Results from the passive acoustic telemetry investigation, conducted over a period between 10 and 22 months, supported these findings showing that the majority of tagged adult sharksexhibited temporally and spatially variable residency patterns interspersed with migration events. Ten individuals undertook coastal migrations that ranged between 433 and 709km (mean = 533km) with eight of these sharks returning to the study site. During migration, individuals exhibited rates of movement between 2 and 59km.d-1 (mean = 17.58km.d-1) and were recorded travelling annual distances of between 450 and 3760km (mean = 1163km). These findings suggest that adult bull sharks are not the sedentary species once thought to be but rather, consistently move over broad spatial scales on the east coast of southern Africa and play an important predatory role shaping and linking ecological processes within the southwest Indian Ocean.

This project provided an exceptional opportunity to describe diving behaviour, movements and to characterise critical habitats of blue sharks in the North-eastern Atlantic using satellite and archival telemetry.  Tracked blue sharks displayed southward movements away from the tagging areas, exhibiting pronounced site fidelity to localised high-productivity frontal regions.  Blue sharks also displayed a high degree of variability in vertical movements. Shifts in diving behaviour were detected both within and between individuals, whereas behavioural phases were linked to the thermal structure of the water column in coastal areas, and to changes in prey distribution or type in offshore regions.  High resolution data showed that blue sharks shift between Brownian (in productive habitats) and Lévy (less productive waters) behaviours.  Vertical movements ranged from the surface to 1160 m, and water temperatures varied between 7.2-27.2°C.  Behavioural data was also crucial in determining the degree of spatial and temporal overlap, and thus vulnerability, between blue sharks and high-seas longliners.  Confirmed fishing mortality was ~11% with four tagged sharks caught by surface longliners.  Simulations showed that boats/sharks overlap was higher in winter and early spring, with the majority of simulated sharks (~88%) at risk at least one day year-1.  Our results indicate that, depending on which geographical regions are occupied at specific times, different segments of the blue shark population face differential risk from longlines.  Sequencing of mitochondrial DNA suggested an absence of spatial genetic differentiation throughout the North Atlantic, providing strong evidence that blue sharks comprise a single population in this region.

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.

Le nourrissage artificiel de requins présente d'importants enjeux écologiques et sociétaux en raison de son impact environnemental mal connu et de la forte controverse publique qui complique sa gestion. Cette thèse propose une réflexion au carrefour des sciences naturelles et sociales, en étudiant la réponse comportementale des requins en termes d'organisation sociale et de déplacements spatiaux, ainsi que le rôle des perceptions sociales dans une meilleure caractérisation du conflit social sous-jacent. Nous décrivons la place centrale des sites de nourrissage dans les réseaux de déplacement des requins tigre et requins citron, et montrons les capacités des requins citron adultes à développer des stratégies comportementales adaptées au contexte de compétition inhérent aux activités de nourrissage. Nous effectuons une interprétation fonctionnelle de tous les effets du nourrissage décrits à ce jour et mettons en évidence une cascade d'effets majoritairement délétères se répercutant de l'échelle individuelle à l'échelle de l'écosystème. En caractérisant la dimension humaine de cette relation particulière entre Homme et Requin, nous identifions les principaux facteurs du comportement des usagers de la mer vis-à-vis du nourrissage et discutons le développement de l'activité selon les lois de l'offre et de la demande comme le principal facteur de risque à l'apparition de mauvaises pratiques et les effets pernicieux qui leurs sont associés. Les approches entreprises au cours de cette thèse illustrent la complémentarité des sciences naturelles et sociales dans la caractérisation et la gestion des relations entre société et ressources naturelles. / Artificial shark provisioning bears critical ecological and societal stakes because of its underinvestigated environmental effects and the strong public controversy that undermines management plans. This thesis aims at combining natural and social science approaches to characterise both (1) the behavioral response of tiger and sicklefin lemon sharks that are targeted by provisioning operations and the (2) role of public perceptions in better apprehending the latent social conflict. We describe the central place of provisioning sites in the movement networks of tiger and sicklefin lemon sharks and describe the capacity of lemon sharks to develop behavioral strategies that are adapted to the competitive context that is inherent to provisioning operations. We provide a functional interpretation of all effects of provisioning reported so far in the literature and highlight cascading and predominantly deleterious effects through the individual to the ecosystem-scale. By investigating the human dimension of this case of human-shark interactions, we identify the main drivers of both operator and ocean user behavior and discuss the unregulated expansion of shark provisioning activities as the main factor of risk to the emergence of bad practices and the associated pernicious effects. The approaches presented in this thesis highlight the advantages of combining natural and social sciences for a better characterization and management of the interaction between society and natural resources.