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

Large population declines for sand tiger sharks (Carcharias taurus) in parts of its global range are well documented, resulting in a strong need for biologically informed conservation and management measures. Although sand tigers in the western North Atlantic have been listed as a Species of Concern by the US government since 1997, details of their seasonal migratory movements and especially vertical habitat use patterns along the US East Coast are limited. Understanding these movement patterns is vital to reducing fishery-related mortality of these sharks and informing other management efforts aimed at recovery of their stocks in the US Atlantic. Although survey and fishery-dependent data have revealed a general picture of the seasonal distribution patterns of sand tiger sharks, details of the areas specifically used by these sharks and their movements between such areas remain unclear. Additionally, information on vertical habitat use such as preferred depth and temperature, as well as variability observed among sexes, size classes and geographic locations would provide insight into the fine-scale distribution of sand tigers to aid better management practices. Here, I report on the horizontal and vertical movements of sand tiger sharks along the US East Coast determined through use of pop-up archival transmitter (PAT) tags and supplemental acoustic telemetry. PAT tags were deployed on 14 sand tiger sharks in Delaware Bay in late summer 2008. Sufficient archived depth and temperature data were obtained from 11 sharks (eight male, three female), and sufficient light data allowed construction of long-term horizontal tracks for 10 sharks (seven male, three female) using a Kalman filter state-space model. Duration of tag deployment per animal ranged from 64-154 days ( =121.6). All seven male sharks left Delaware Bay in late summer/early autumn and migrated south along the US East Coast reaching waters off North Carolina, where they remained until transmitter detachment during the winter months. In contrast, all three females moved out of Delaware Bay into deeper, offshore waters east of the bay near the continental slope. During southern migration of males, average depth utilized was positively correlated to shark size. The smallest males spent on average over 90% of their time in waters <40 >m, whereas intermediate and large sized males spent only 54 and 38% of their time at depths <40 >m, respectively. Female sharks spent an average of 46% of their time in waters range, spending at least 95% of their time in waters 17-23oC, with little difference between size classes or sexes. Horizontal movements of male migrating sand tigers also revealed several areas of concentrated activity along their southern migratory routes. Migratory patterns of sand tiger sharks along the US East Coast appear most similar to patterns displayed by this species along the coast of South America. Further delineation of western North Atlantic continental shelf and slope core areas of sand tiger shark activity, especially for females, will inform efforts to reduce interactions with commercial fisheries and measures to avoid habitat degradation - management aspects that will aid in reducing mortality and enhance rebuilding of sand tiger stocks along the US East Coast.

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