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Sharks, rays and skates (elasmobranchs) are a group of cartilaginous fishes currently facing mass declines from overfishing. As of 2014, 25% of elasmobranch species were classified as threatened with extinction by The International Union of the Conservation of Nature (IUCN) Red List. It is estimated that 100 million are killed every year through illegal, unregulated and unreported (IUU) fishing, often for their fins which are in high demand for shark fin soup. As elasmobranchs have been on the planet for nearly 450 million years, the function that each species has within the environment is vital for the marine food web structure and function which ultimately regulates biomass density and therefore balancing ecosystem functions. However, more information is still required on the general biology and population structure of most elasmobranch species, which will assist in management at in-situ and ex-situ sites, to conserve populations. To address some of these issues, this thesis uses a range of molecular techniques to investigate species identification and population dynamics by genetics and non-invasive/non-intrusive tagging methodologies. All samples collected and analysed were either a discard elasmobranch product from fish markets or from non-invasive/non-intrusive mucus swabs, which ensures each chapter has not contributed to the decline of wild populations. By focusing on non-invasive techniques, the thesis developed a new method of collecting non-intrusive DNA samples by mucus swabbing individuals underwater, collected by scuba divers. Non-intrusive and invasive discard product samples from the undulate ray Raja undulata revealed 6 new distinct genetic clusters throughout their distribution and the application of capture mark-recapture using photographs and recognition software provided consistent population sizes and evidence of female to female or female to male pairing between individuals. Photo recognition was also successfully applied to the small-spotted catshark Scyliorhinus canicula in early-stage development (within the first 60 weeks of life) as an alternative for invasive tagging, especially focusing on ex-situ conservation. Genetic analysis using microsatellite markers was applied to two species of captive sharks for ex-situ management and found genetically diverse populations with little signs of inbreeding. Wild samples of discard products of elasmobranchs and chimaeras (chondrichthyans) caught in Morocco in June 2015 and 2016 were utilized for two chapters. By employing DNA barcoding methods and observational field methods, the first analysis of the diversity of chondrichthyans was conducted and provided evidence of targeted fishing for elasmobranchs and IUU fishing. These samples were also used to investigate the ability of identifying the proteins in elasmobranch fins, which could possibly be applied as an alternative method of identifying species. We found that 5 main protein groups define the composition of elasmobranch fins; collagen, actin, tubulin, tropomyosin and myosin. Finally, the use of genetics found the first evidence of twins and heteropaternal superfecundation, whereby twins were formed from two different fathers in the same egg. Following the outcomes of the thesis, further research is advised to focus on revealing and understanding the full genome sequence of species to better understand individual characteristics and population differences, which may influence the their success or demise for future conservation. As elasmobranchs continue to decline, it is imperative that further studies are not only conducted but applied in order to conserve elasmobranchs for the future. The outcomes of this thesis have successfully generated a deeper understanding of the biology, connectivity and utilisation of elasmobranch populations in both in-situ and ex-situ sites. However, it is the responsibility of scientists and governments to continue the research into elasmobranch biology and population structure, to influence management, conservation and social change.

Commonly addressed as the apex predator in the oceans, elasmobranchs play an important role in keeping the balance of a healthy marine ecosystem. About a quarter of all elasmobranchs are threatened by extinction mainly due to human activities, such as overfishing, destructive fisheries and shark finning. Elasmobranchs are vulnerable to extinction due to their slow growth, late sexual maturity, and low offspring production. Some oviparous elasmobranch species lay their sessile egg cases around shallow waters of the intertidal zone, where they are exposed to extreme environments, e.g. high temperatures and low dissolved oxygen levels. Climate models predict that CO2 levels will increase to 1100 ppm by 2100, which leads to ocean warming, as well as the extent and frequency of low dissolved oxygen zones. However, only few studies have considered the effect of elevated temperatures and low dissolved oxygen levels on biological fitness and physiological performances of elasmobranchs, especially during crucial embryonic stage. We developed an alternative scale for staging embryonic development non-invasively in living embryos (Chapter III), and then used this scale in later work to determine biological fitness, physiological performances and survival at specific developmental stages. This PhD research is therefore aimed to investigate the effect of both current extreme environments and predicted future climatic conditions, specifically ocean warming and hypoxia, on growth and survival (in Chapter IV), and metabolism (in Chapter V) of small-spotted catshark, Scyliorhinus canicula during early ontogeny. Our results revealed that exposure to elevated temperatures increase the embryonic growth, yolk consumption and metabolic rates of S. canicula, while shrinking the hatchling size. Under hypoxic conditions, S. canicula embryos showing a steady growth, but metabolic rates were significantly reduced, suggesting that S. canicula may have incorporated anaerobic metabolism during this period. As the incubation period was longer in hypoxic treatments, embryonic survival was negatively affected as the animals trapped longer inside the sessile egg cases under low dissolved oxygen conditions. The synergistic effects of both ocean warming and hypoxia increased mortality rate of S. canicula during early embryonic stages. To mimic the free-living hatchling stage that are free to swim in a preferred environment, S. canicula hatchlings were then transferred into a common environment (normoxia, 15 °C), where metabolic performances were re-measured after 1-week. Our results revealed that developmental environment does not have a lasting impact on metabolism of S. canicula hatchlings. Understanding the impacts of future predicted climate change on ecological and physiological aspects of elasmobranchs is essential from a conservation standpoint in order to accurately determine, predict and eventually reduce the consequences of human activity on marine habitats as well as the species within them.

Determining the dynamic nature of animal movement has been an important component in a wider understanding of animal population ecology. Generally, this is because temporal change in the density of a population at a specific geographic location is not only a function of births and deaths but also of movements, including migration. The increased availability of remote telemetry and biologging systems in recent years has enabled many studies tracking marine predators, such as turtles, seabirds and marine mammals, but a general understanding of spatial dynamics in large sharks remains less well developed. This is in part due to few studies having achieved sufficiently long-term, multi-year tracks to detect changes in movement behaviour over time. Determining the timing, repeatability and potential motivations for movements of large sharks is necessary to understand the ecological and evolutionary role of such behaviour more generally in marine predators. Furthermore, given global concerns of declining shark populations, a detailed appreciation of shark movements can reveal the extent 6 of overlap with area-focused human activities (e.g. fishing), as well as inform assessments of population trends and spatial management options. In order to demonstrate how shark migratory behaviour and spatial dynamics can vary dramatically depending on the species and location, with subsequent contrasting conservation implications, the present work used longterm, remote telemetry to reveal detailed patterns in shark movement behaviour at two very different geographical scales: broad-scale movements of larger species that encompass ocean basins, versus fine-scale movements of reef-associated species at a remote atoll. First, using satellite telemetry, it was revealed for the tiger shark Galeocerdo cuvier, that adult males undertake annually repeated, roundtrip migrations of over 7,500 km in the northwest Atlantic. Second, acoustic telemetry was used to determine the fine-scale spatial dynamics of a multispecies shark assemblage at a small, remote atoll in the Seychelles, Indian Ocean, where a number of species displayed perennial residency. While the fine-scale movements of reef sharks in the Seychelles suggest an MPA of moderate size may be an effective management option, the long-distance migrations of the tiger sharks in the Atlantic reveal that conservation efforts targeting them must account for dynamic fisheries interactions over large geographical scales, potentially requiring time-area closures to be effective. Examining the long-term movement behaviour of different shark species over contrasting geographical scales has emphasised the importance of understanding spatial dynamics when informing management decisions, and has contributed to a wider understanding of the population ecology of these species.

Sharks are some of the most well adapted and effective animals in the animal kingdom. Unfortunately, they are also some of the most feared. For many people the word shark evokes images of vicious attacks like those seen in movies such as Jaws. Sharks have also been negatively portrayed in the media. This negative portrayal of sharks has led to misconceptions about sharks that have damaged their populations. Efforts have been made to raise awareness and fight common misconceptions of sharks. However, many people still hold on to the incorrect ideas they have about sharks. This thesis will examine the negative impact that the media has had on shark populations. It will also examine the role that sharks play in marine ecosystems to raise awareness about these animals. After researching this issue, a literature review was conducted in addition to case studies and visual analyses. This research will inform my final visual solution for this thesis project. I will be creating an educational comic book that addresses the issue of shark conservation and raise awareness of the issues that sharks face. In this comic book I will use illustration, typography, and color theory to create a cohesive visual narrative. In addition, I will be creating a web banner ad as well as three social media ads for this project.

Small-scale fisheries (SSF) are poorly documented, yet 90% of the 120 million employed in capture fisheries work in the SSF sector and >1 billion people globally rely on fish as an important source of protein. There is a lack of data on the status of the majority of fisheries in Madagascar owing to the difficulty in surveying the vast coastline and large number of small-scale fishers. In Madagascar, marine turtles and elasmobranchs are important culturally and as sources of income and food for many small-scale fishers. However, very little data exist on the status of these two animal groups. The five chapters of this thesis intend to increase our understanding of the status of marine turtles and elasmobranchs in Madagascar. This is achieved through the assessment of the fisheries, legislation and in the case of turtles, the nesting population. I also document community-based methods for monitoring fisheries and marine turtle nesting, that are easily replicable for gathering data across remote regions. Results show that the turtle fishery in Madagascar appears to have remained at the same level since the 1970s, despite being illegal since the 1990s, with landings estimated to be approximately 10,000 to 16,000 turtles.year-1. To further contextualise the take of turtles in Madagascar, by carrying out a global review, I estimate that the worldwide legal take in turtle fisheries to be over 42,000 turtles.year-1. Contrary to reports from fishers, actual numbers of elasmobranchs (the majority of which are sharks) taken by the traditional (non-motorised) fishery has not declined. Results support previous reports that fishing effort has increased, as well changes in fishing gears, to account for declining catch per unit effort (CPUE) to maintain shark landing numbers. Furthermore, the size of some shark species has significantly declined, even across this study. Community-based turtle nesting monitoring and protection in western Madagascar revealed a small, yet potentially significant, nesting population. Across the 17 current nesting sites recorded, the majority of nesting populations in Madagascar have <50 nests.year-1. A further >40 historic nesting sites were recorded. Community-led monitoring methods not only helped to fill a data gap, but were also found to reduce loss of nests through human disturbance. Misinterpretations, poor enforcement and gaps in current legislation mean that both marine turtles and elasmobranchs are effectively unprotected from overexploitation. This thesis provides recommendations for improved legislation and management of both groups of species and demonstrates that participatory monitoring methods can not only reduce data deficiency, but enhance locally-led management and protection, and increase Madagascar's capacity for improved management and conservation.

Shark tagging is used as a source of data for shark migration and behaviors. Different tags can collect temperature, salinity, or depth data points while the shark is in motion. There are a variety of shark tagging methods used to monitor sharks. Of these methods, shark bolting has caused some concern. Shark bolting is the method of drilling holes into the first dorsal fin of pelagic sharks and placing steel screws into the fin to secure a satellite (SAT) tag. Bolted SAT tags cause concern due to the limited ways of removal, high probability of excessive biofouling, infections, and increased drag while swimming in many species of sharks. The objective of this study is to assess if bolting is a non-impact shark tagging method in terms of resulting shark health and behavior and, further, whether it should be considered a humane or inhumane practice by examining the present knowledge of dorsal fin anatomy and functionality.

The epidermal microbiome of sharks is hypothesized to be consistent across individuals of the same species, regardless of biogeographical influence, suggesting that there are mechanisms that are recruiting and maintain the microbial community. To explore this hypothesis, I conducted an extensive investigation into the epidermal microbiomes of the leopard shark (Triakis semifasciata) across environments and an acute temperature shift. I also tested phylosymbiotic trends between epidermal microbiomes and respective benthic shark hosts. Initially, my research involved the analysis of T. semifasciata's microbiomes in captive, semi-captive, and wild settings. The associated microbiomes demonstrated comparable taxonomic community structure and maintained biodiversity irrespective of the captivity status of the hosts, therefore suggesting the host maintains a consistent microbiome even when born into captivity, and when the host experiences a change in habitat. For my next research chapter, I explored the influence of their evolutionary lineage and physical traits on their skin microbiomes by investigating three benthic shark species, horn (Heterodontus francisci), leopard (Triakis semifasciata), and swell shark (Cephaloscyllium ventriosum). This phase underscored the strong correlation between the diversity of skin microbiomes and the host's phylogenetic lineage, while the relationship with inter-denticle distance was less robust, affecting individual species within the microbiome. Finally, I examined the impact of thermal shifts on T. semifasciata's epidermal microbiomes to investigate the ability of the microbiome to tolerate the effects of global warming. The microbiomes underwent significant alterations of community compositions and functional pathway profiles following temperature changes, suggesting complex adaptive responses. Despite these compositional shifts, the dispersion of these communities remained consistent across temperatures, suggesting degree of resilience or stability in these microbial ecosystems. My research holds significant implications, particularly in the context of anticipated global ocean warming trends and human-induced pressures on marine ecosystems. It not only enriches our understanding of benthic shark ecology, but also underscores the need for more research on marine organisms' microbial community responses to temperature change.

Shark populations worldwide have been depleted by overfishing, yet empirical evidence of shark abundance and diversity before human impact is scarce. Without long-term data to document the timing and magnitude of shark declines, it is challenging to understand how the loss of these high-level predators has reshaped ecosystems and set meaningful management targets informed by natural variability. In this dissertation, I use fossil shark scales (dermal denticles) to reconstruct shark communities on coral reefs over the last several millennia. After finding denticles to be well-preserved in reef sediments, I refined an extraction method and built a reference collection to facilitate denticle classification. By measuring denticle shedding in captive sharks, I showed that shedding rates vary across sharks with different life modes, thereby influencing how shark communities are represented as denticle assemblages in the fossil record. I then calibrated the denticle record by comparing denticle assemblages preserved in surface sediments with wild shark populations on a remote, unfished atoll. I found that denticle accumulation rates were positively correlated with shark abundance and that denticle assemblage composition was consistent with commonly observed shark species. Building on this foundation, I recovered denticles from mid-Holocene and modern reef sediments in Caribbean Panama to define a local shark baseline before major human impact and quantify shifts in the modern shark community from this historical reference point. Denticle assemblages indicated that shark communities in this region declined threefold since the mid-Holocene and were functionally restructured by both long-term harvesting and habitat modification. Together, this work demonstrates that the denticle record can reveal changes in shark communities over long ecological timescales, helping to contextualize contemporary abundances and inform shark management and ecology.

Industrial fisheries threaten oceanic sharks and rays. Effective management and conservation responses require solutions that incorporate biological, ecological, and policy considerations. In this dissertation, I use an interdisciplinary approach to measure and mitigate fisheries impacts for data-poor but highly threatened pelagic elasmobranchs. First, I describe the quantity, composition, and potential impact of industrial tuna fishing on 22 elasmobranch species using catch data reported by global tuna fisheries and a catch estimation approach. I show that publicly accessible catch rates indicate that these fisheries report ~2.9 million individual sharks and rays per year, but that estimated catches are as much as five times higher. Importantly, these impacts are understudied: only 20% (15 of 76) of the examined populations had been formally assessed and of these, roughly 30% are overexploited. Given these findings, in the second chapter I focus on one particularly vulnerable group: manta and devil rays (collectively, Mobulids). I analyzed the genetic population structure of three species in the eastern Pacific Ocean and found weak but statistically significant population genetic structure among all four species. These findings suggest that Mobulids exhibit metapopulation structure and local selection occurring regionally in the eastern Pacific, and support the identification of unique regional units for conservation and fisheries management. Finally, and as a way forward, I assess the policy response of five large tuna Regional Fisheries Management bodies responsible for managing and mitigating to elasmobranch bycatch. Using a mitigation hierarchy framework, I show that current policies are not adequate to sufficiently reduce oceanic shark and ray bycatch, and make management, data, and transparency recommendations that are likely to reduce the impacts of bycatch on threatened sharks and rays.

Ectotherms, including sharks, behaviorally thermoregulate in order to optimize physiological processes. Juvenile sharks often utilize estuaries, which can provide warm water temperatures that increase metabolism and facilitate growth. Both the California Horn Shark (Heterodontus francisci) and the Leopard Shark (Triakis semifasciata) occupy estuaries of southern California as juveniles and represent contrasting activity levels; horn sharks are relatively sedentary while leopard sharks are more active and mobile. The primary aim of this study was to better understand the relationship of behavioral thermoregulation and metabolism in response to temperature in these two species. The objectives were threefold: 1) identify the temperatures juveniles prefer, 2) assess the sensitivity of metabolism (Q10) to temperature via measurements of oxygen consumption, and 3) compare these results between species, sex, and seasonal acclimation treatments. Using a shuttlebox, this study showed juvenile horn sharks and leopard sharks have comparable thermal preferences and temperature ranges. Respirometry trials at different temperatures showed both species exhibited increasing metabolic rates with increasing temperature, and leopard sharks exhibited higher metabolic rates than horn sharks across all temperatures. However, horn sharks exhibited a higher overall Q10 suggesting their metabolism has greater thermal dependence. Underlying acclimation to seasonal temperatures did not appear to have an effect on any of these parameters. Horn sharks likely target environments (i.e., day-time resting places) closer to their preferred temperature and more stable in temperature fluctuation than leopard sharks. Lab-based determination of physiological and behavioral responses to temperature are important in understanding habitat usage during vulnerable life stages.

This project endeavored to provide a formative, contemporaneously applicable, and fully quantitative baseline of a significant component of the shark harvest produced by the nation of India, namely, the longline bycatch mortality for sharks generated from the commercial-scale fishing activity in the extensive oceanic region of India’s Exclusive Economic Zone (EEZ), the nature and scope of which is little understood. Worldwide, shark populations have experienced marked declines due to the advent of modern industrial fishing. Additionally, the life-history and reproductive characteristics of these species, which include longer lifespans, slower growth, fewer offspring, and generally reduced fecundity, constrain group level reproduction and replacement rate compared to that of many commercially targeted and managed teleosts. Although generally true at a global level, shark population depletion has varied in nature and/or rate around the world, with significant unknowns persisting in relation to the waters and seas surrounding developing and recently developed economies; in many cases these waters have not been subject to comparable levels of oversight, active management, and/or assessment as those found in other more established global fisheries. India, over the last decade and a half approximately, has been positioned as the second largest contributor to the global shark harvest in terms of overall tonnage which in turn raises the following question: Is this country mirroring similar global trends of shark population decline due to its fishing activity? Addressing this question in a formatively useful way defines the focal pursuit of this research venture. A relevant, significant, though sparsely assessed source of shark fishing mortality experienced within the broader Indian EEZ—non-target bycatch of sharks, specifically that which is generated from the oceanic longline (LL) fishery—was ultimately analyzed to address the primary hypothesis: Although only one among many marine sub-fisheries, the unassessed status of the oceanic LL fishery presently obscures a reality of unsustainable harvest, such that the community of shark species/stocks extant within the oceanic sector of the Indian EEZ are incurring unsustainable levels of fishing mortality (F) through bycatch in longline gear. To examine the impacts of longline fishing on shark populations in the Indian EEZ, this study utilized advanced statistical methods that focus on the rapid assessment of data limited stocks. In particular, a data-limited status assessment methodology devised by Shijie Zhou and various colleagues—known as the Sustainability Assessment for Fishing Effects (SAFE) method—and Bayesian Hierarchical Analysis were applied. The use of the former afforded a tractable method for longline bycatch mortality estimation (F) through the relationship among target species mortality, a number of bycatch species’ catchability parameters, and spatial overlap of fleet fishing effort with bycatch species habitat. Key outputs were defined as parameters or logical functions thereof within said Bayesian hierarchal models and mean posterior estimates were derived. Two separate Bayesian Models where constructed and run using the OpenBUGS statistical software. The first was designed to derive a marginal posterior distribution of fishing mortality (F), and the second was used to produce marginal posterior distributions of the following biological reference points: Fmsm, Flim, and Fcrash. Fmsm equals the instantaneous fishing mortality rate that corresponds to the maximum number of fish in the population that can be killed by fishing in the long term; Flim equals instantaneous fishing mortality rate that corresponds to the limit biomass Blim, where Blim is assumed to be half of the biomass that supports a maximum sustainable fishing mortality (0.5Bmsm); Fcrash equals minimum unsustainable instantaneous fishing mortality rate that, in theory, will lead to population extinction in the long term. These reference points were derived via integration with respect to the specific parameter across all model-defined upstream conditional dependencies; the relationships where showcased in formal terms using a series of Directed Acyclic Graphs (DAG) and a defined graphical lexicon. The evaluation of integrals was accomplished via large iteration Monte Carlo Markov Chain simulation using a Gibbs sampling algorithm within the OpenBUGS software suite. Mean values (estimates) of corresponding marginal posteriors as well as their credible intervals acquired via simulation were equivalent to point values for the otherwise unknown parameters of interest. Once acquired, these values were then elevated for usage in a final, species-specific status determination based on a straight forward value relationship, specifically between Instantaneous Fishing Mortality (F) and a corresponding set of biological reference points (Fmsm, Flim, Fcrash). The relationships and corresponding species status determinations were garnered using the Credible Interval (CRI), which is the Bayesian analogue to the frequentist Confidence Interval, as follows: F < Fmsm, = Low-Risk (L; i.e. sustainable mortality); F ≥ min[Fmsm] or F + 95% CRI ≥ Fmsm, = Precautionary medium risk (m); Fmsm ≤ F < Flim,= Medium risk (M); F ≥ min[Flim] or F + 95% CRI ≥ Flim, = Precautionary high risk (h); Flim ≤ F < Fcrash, = High risk (H); F ≥ min[Fcrash] or F +95% CRI ≥ Fcrash, = Precautionary extreme high risk (e); and F ≥ Fcrash, = Extreme high risk (E). Fcrash is the level at which minimum, unsustainable fishing mortality has been achieved, which, when maintained over the long-run, results in local/population extinction. Values in still greater excess thereof further intensify the rate of depletion towards that eventuality. Spanning the time period 2010-2014, both for individual years and as a grand mean thereof, Fishing mortality (F) estimates were generated for (30) species of sharks, all of which, either exclusively or in part, are known to inhabit the oceanic ecosystem of the Indian EEZ. Biological reference points Fmsm, Flim, Fcrash were produced for 17 (of 30) species. Additionally, point values for other relevant parameters were derived (e.g. natural mortality [M]) for 17 species , some of which are new within the scientific literature (specifically the Longfin Mako (Isurus paucus) and possibly the Gulper Shark (Centrophorus granulosus for the Indian Ocean Stock). Others include the mean, year-wise longline yellowfin tuna (YFT; Thunnus albacares) catch (C) within the Indian Oceanic EEZ, and the average area of longline fishing impact within the Indian Oceanic EEZ. The fishing mortality values derived in this study may likely be the first values in the literature for many of the species evaluated, at least in the context of the Indian Ocean and certainly for the India EEZ. Of the 17 shark species for which both F and corresponding biological reference points (Fmsm, Flim, Fcrash) were derived, one species was defined as Low Risk, one as Precautionary Medium Risk, three as Precautionary High Risk, one as High Risk, two as Precautionary Extreme High Risk, and nine species as Extreme High Risk. Many of the species represented in the higher risk categories are currently subjected to trade control and general protection under both the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the Convention on Migratory Species Protection Agreement (CMS); India is a ratified member Party to both conventions and thus is theoretically obliged to respect/implement necessary control actions.

The Georgia shrimp fishery has seen a dramatic decrease in profit and productivity since the 1980’s due to a number of economic factors. Additional, yet undocumented, pressures on this fishery include interactions between foraging sharks with trawl gear. Fishermen report that sharks frequently bite nets in an attempt to prey on netted fish, resulting in large holes in the gear. Further elasmobranch interactions with trawl gear occur as bycatch; shrimp trawls represent nearly 100% of elasmobranch commercial bycatch in Georgia state waters, the species composition of which is largely unstudied. Shark interactions with nets were detailed through fishery-dependent observations on commercial shrimp boats in Georgia (n= 6 vessels). Number of damaged sites, location of damage on the net, estimated repair time, and many fishing/environmental variables were recorded for 96 trawling events May 2016 - November 2017. Sharks bit on average 1.51 holes (± 0.2 SE) in the nets for every trawl. Shark depredation was correlated negatively with vessel speed (r=-0.2814, p=0.005), and positively with the duration and number of nets (r=0.2799, p=0.006). As a result, fishermen spent of average estimated time of 27 minutes repairing equipment for every trawl they make in a day of fishing. Fishermen were also asked questions related to their perceptions towards this issue for qualitative analysis. Elasmobranch bycatch was also identified and measured for each trawl. Of fifteen total species caught, three species in particular accounted for 76.7% of all elasmobranch bycatch (n=84 trawls, 2247 individuals): Rhizoprionodon terraenovae (CPUE = 4.2 individuals/hm2 area trawled ± 0.83 SE), Hypanus sabinus (CPUE =1.736 ± 0.29), and Gymnura micrura (CPUE =1.6 ± 0.22). Because the fishery has decreased in size and effort over the last two decades, further analysis and monitoring is needed to determine if bycatch in shrimp trawls are drastically decreasing stock sizes in elasmobranch species.

What did coral reef ecosystems look before human impacts became pervasive? Although we cannot effectively manage the marine environment without knowledge of what it looked like in a pristine state, human impacts have wreaked such havoc on the ocean that it is often impossible to accurately characterize marine populations pre-exploitation. Lacking a baseline is particularly critical for species of conservation concern such as sharks, which have experienced severe population declines at local and global scales. I use the unique setting of Palmyra Atoll, a remote, U.S. National Wildlife Refuge in the central Pacific Ocean, to describe the population dynamics, ecological characteristics, and behavior of reef sharks absent significant human impacts. With a combination of extensive field surveys and experiments and spatially and temporally explicit analytical tools, I attempt to resolve a set of ecological debates regarding the trophic structure of coral reef communities, the drivers of life history variability, and the ecological effects of non-consumptive human impacts on marine predators. Ultimately, I find that the trophic structure of an unexploited reef fish community is not inverted and that even healthy top predator populations may be considerably smaller, and more precarious, than previously thought (Chapter 1). At the same time, I show that there is substantial but not predictable variability in life history traits observed for the grey reef sharks across its range, suggesting that regional management may be necessary to set sustainable harvest targets and to recover this shark species globally (Chapter 2). Finally, I demonstrate that humans can interact with reef sharks without persistent behavioral impacts, and that well-regulated shark diving can capture the economic benefits of tourism without undermining conservation goals (Chapter 3). Throughout this dissertation, I focus on coral reef associated shark species, but the challenges I consider and the methods I employ are important for many systems and many predators, which tend to move more than their prey. We often find ourselves managing a moving target, and so counting things correctly, assessing ecological variability, and understanding behavioral responses due to human interactions with wildlife can profoundly change the way we understand and manage both terrestrial and marine systems.

This is a collection of fifteen short stories written between the summer of 2009 and the fall of 2012.

Cartilaginous jaws have historically been considered primitive in comparison to those of bony fishes. Yet sharks are capable of cutting through materials, such as bone and sea turtle shells, which are paradoxically harder than the jaws themselves. To examine feeding mechanisms in sharks, I used finite element analysis (FEA) to digitally reconstruct the jaws of four shark species: the sandtiger (Carcharias taurus), great white (Carcharodon carcharias), tiger shark (Galeocerdo cuvier) and bull shark (Carcharhinus leucas). I developed a new method for material testing shark jaw cartilage. Using this method I obtained multi-directional species-specific mechanical properties for jaw cartilage and incorporated these data into the models. I also examined differences between species and ontogenetic changes in mechanical properties of jaw cartilage. The data show several adaptations of shark jaws that are discussed in relation to feeding mechanics. Comparison of the jaws of macropredatory species to the crushing jaws of the Port Jackson shark (Heterodontus portusjacksoni) show that there are directional differences in the material properties of jaw cartilage that are consistent with feeding behaviour in sharks. Furthermore, the data suggest that the jaws of subadult great whites are mechanically vulnerable when handling large prey. Ontogenetic mineralisation of the jaws is thus considered necessary to feed on large marine mammals. This hypothesis is supported by the finding that the jaws of the bull shark stiffen with age. As with the great white, the bull shark undergoes dietary shifts to large mammalian prey. Surprisingly, the data reveal that the jaws of sharks are an order of magnitude less stiff than previously believed. This flexibility is exemplified by the highly compliant jaws of the tiger shark, which are here hypothesised to conform to the shape of turtle shells during biting. Close contact between the jaws and teeth may enhance sawing through hard materials by the uniquely shaped teeth of the tiger shark.

Female dolphins were watched from a small motorboat. Locations within the 150 km$\sp2$ study area were determined either by triangulation from compass bearings or latitude and longitudes from a GPS. Animals were individually identified by natural markings on their dorsal fins. Sexes were determined by observation of genitals or offspring; 113 were known females. Most analyses include data from 18-43 females collected during some or all of 1984-1993. Females initially gave birth at 12-15 years during a spring/summer birth and conception season. Birth intervals were no less than 4 years unless the preceding infant died. Offspring were weaned at 3.5-7.5 years, always within a year preceding birth of the next infant. First-year infant mortality was 37%, accumulating to 50% by age 4. Ranges of adult females were 8-58 km$\sp2$ (with one exception at 5 km$\sp2).$ Range overlap between females was 0-85% with little evidence of territoriality. Some females used different ranges in summer and in winter, others used the same ranges year round. Weaned daughters continued to use their mothers' ranges and continued to associate with their mothers regularly. Despite continued use of their mothers' ranges post-weaning, weaned sons tended to cease associating with their mothers. Adult females swam together regularly but interacted infrequently. One distinctive interaction, termed pairing consisted of a female pair remaining together in a stereotyped position, typically in contact. Pairing was performed in bouts lasting 5-90 minutes. Unlike the general adult female population, pairing females, in 35 cases involving adults, were, with one known exception, always cycling or pregnant. Four such females were attended by infants at least 2 years old. Subadult females also paired similarly with either adults or other subadults. Pairing was associated with the presence of males and may be cooperation by females to thwart coercive male mating efforts.