Intraguild processes drive space-use patterns in a large-bodied marine predator community.

Interspecific interactions, including predator-prey, intraguild predation (IGP) and competition, may drive distribution and habitat use of predator communities. However, elucidating the relative importance of these interactions in shaping predator distributions is challenging, especially in marine communities comprising highly mobile species. We used individual-based models (IBMs) to predict the habitat distributions of apex predators, intraguild (IG) prey and prey.

Widespread diversity deficits of coral reef sharks and rays.

A global survey of coral reefs reveals that overfishing is driving resident shark species toward extinction, causing diversity deficits in reef elasmobranch (shark and ray) assemblages. Our species-level analysis revealed global declines of 60 to 73% for five common resident reef shark species and that individual shark species were not detected at 34 to 47% of surveyed reefs. As reefs become more shark-depleted, rays begin to dominate assemblages.

Energetic connectivity of diverse elasmobranch populations - implications for ecological resilience.

Understanding the factors shaping patterns of ecological resilience is critical for mitigating the loss of global biodiversity. Throughout aquatic environments, highly mobile predators are thought to serve as important vectors of energy between ecosystems thereby promoting stability and resilience. However, the role these predators play in connecting food webs and promoting energy flow remains poorly understood in most contexts.

Vertical space use and thermal range of the great hammerhead (Sphyrna mokarran), (Rüppell, 1837) in the western North Atlantic.

The great hammerhead (Sphyrna mokarran) is a highly mobile, large-bodied shark primarily found in coastal-pelagic and semi-oceanic waters across a circumtropical range. It is a target or by-catch species in multiple fisheries, and as a result, rapid population declines have occurred in many regions. These declines have contributed to the species being assessed as globally critically endangered on the IUCN Red List.

Thirty-five years of tiger shark Galeocerdo cuvier relative abundance near Bimini, The Bahamas, and the Southeastern United States with a comparison across jurisdictional bounds.

Abundances of large sharks are reported to have declined worldwide, and in response various levels of fisheries management and conservation efforts have been established. For example, marine-protected areas have been suggested as a means to protect large expanses of ocean from fishing and other industrial activities (e.g.

Predator-prey landscapes of large sharks and game fishes in the Florida Keys.

Interspecific interactions can play an essential role in shaping wildlife populations and communities. To date, assessments of interspecific interactions, and more specifically predator-prey dynamics, in aquatic systems over broad spatial and temporal scales (i.e.

Preliminary observations on the movement ecology of a crested horn shark (Heterodontus galeatus).

The residency and movements of a single acoustically tagged female crested horn shark (Heterodontus galeatus) were monitored in Jervis Bay, Australia. The individual was intermittently detected by receivers throughout the 8-year study period and showed preference for particular rocky reefs in terms of its residency indices and duration of residency events. This individual exhibited lower residency and dissimilar movement patterns to that of the well-studied and sympatric Port Jackson shark (Heterodontus portusjacksoni), highlighting the need for research into the basic life history and movement ecology of H.

Anatomy of the mechanosensory lateral line canal system and electrosensory ampullae of Lorenzini in two species of sawshark (fam. Pristiophoridae).

It has long been assumed that the elongated rostra (the saws) of sawsharks (family: Pristiophoridae) and sawfish (family: Pristidae) serve a similar function. Recent behavioural and anatomical studies have shed light on the dual function of the pristid rostrum in mechanosensory and electrosensory prey detection and prey manipulation. Here, the authors examine the distributions of the mechanosensory lateral line canals and electrosensory ampullae of Lorenzini in the southern sawshark, Pristiophorus nudipinnis and the longnose sawshark, Pristiophorus cirratus.

Personality-driven life history trade-offs differ in two subpopulations of free-ranging predators.

Consistent individual differences in behaviour (i.e. personality) can be explained in an evolutionary context if they are favoured by life history trade-offs as conceptualized in the pace-of-life syndrome (POLS) hypothesis.

Linking local movement and molecular analysis to explore philopatry and population connectivity of the southern stingray Hypanus americanus.

Limited data pertaining to life history and population connectivity of the data-deficient southern stingray (Hypanus americanus) are available. To determine potential vulnerabilities of their populations, this study aimed to analyse their movement patterns and genetic variability. A population of southern stingrays encompassing nine sites around Cape Eleuthera, the Bahamas, has been monitored using mark-recapture, spanning a 2.

Biodiversity assessment of tropical shelf eukaryotic communities via pelagic eDNA metabarcoding.

Our understanding of marine communities and their functions in an ecosystem relies on the ability to detect and monitor species distributions and abundances. Currently, the use of environmental DNA (eDNA) metabarcoding is increasingly being applied for the rapid assessment and monitoring of aquatic species. Most eDNA metabarcoding studies have either focussed on the simultaneous identification of a few specific taxa/groups or have been limited in geographical scope.

Thermal performance responses in free-ranging elasmobranchs depend on habitat use and body size.

Temperature is one of the most influential drivers of physiological performance and behaviour in ectotherms, determining how these animals relate to their ecosystems and their ability to succeed in particular habitats. Here, we analysed the largest set of acceleration data compiled to date for elasmobranchs to examine the relationship between volitional activity and temperature in 252 individuals from 8 species. We calculated activation energies for the thermal performance response in each species and estimated optimum temperatures using an Arrhenius breakpoint analysis, subsequently fitting thermal performance curves to the activity data.

Ultrasonographic and hormonal characterization of reproductive health and disease in wild, semiwild, and aquarium-housed southern stingrays ().

Objective: To characterize physical examination, plasma biochemical, and ultrasonographic findings in aquarium-housed, managed semiwild, and wild southern stingrays () with and without reproductive disease.

Animals: Southern stingrays from aquarium (n = 48), lagoon (managed semiwild; 34), and wild (12) habitats.

Procedures: Limited, opportunistic prosections were performed of presumed anatomically normal wild southern stingrays and compared with findings for aquarium-housed stingrays with reproductive disease.

Global spatial risk assessment of sharks under the footprint of fisheries.

Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries.

Evaluation of Comprehensive Coelomic Fluid Analysis through Coelomic Pore Sampling as a Novel Diagnostic Tool in Elasmobranchs.

The objectives of this study were to describe a minimally invasive coelomic fluid sampling technique in elasmobranchs, to characterize the coelomic fluid composition in clinically normal and abnormal animals, and to compare findings from wild and managed populations. Fluid was collected via the coelomic pore in 89 individuals from 16 species spanning clinically normal and abnormal patients within a managed population (n = 54), a semi-managed open-lagoon population (n = 18), and a wild population (n = 17). Biochemical and cytological fluid analyses were performed on all samples, and bacterial and fungal culture, protein electrophoresis, and cholesterol electrophoresis were performed on a subset of samples.

No apparent negative tagging effects after 13 years at liberty for lemon shark, Negaprion brevirostris implanted with acoustic transmitter.

An intact and uncompromised internal acoustic transmitter was non-lethally recovered from a lemon shark Negaprion brevirostris, after 13 years at liberty. The shark, first tagged at an estimated age of 2 years old near South Bimini, Bahamas in 2004, was recaptured in 2017 with a total length of 264 cm. The tagged shark displayed typical growth rate, pregnancy, natal homing and pupping behaviour of other individuals in this population.

Environmental DNA reveals tropical shark diversity in contrasting levels of anthropogenic impact.

Sharks are charismatic predators that play a key role in most marine food webs. Their demonstrated vulnerability to exploitation has recently turned them into flagship species in ocean conservation. Yet, the assessment and monitoring of the distribution and abundance of such mobile species in marine environments remain challenging, often invasive and resource-intensive.

Does detection range matter for inferring social networks in a benthic shark using acoustic telemetry?

Accurately estimating contacts between animals can be critical in ecological studies such as examining social structure, predator-prey interactions or transmission of information and disease. While biotelemetry has been used successfully for such studies in terrestrial systems, it is still under development in the aquatic environment. Acoustic telemetry represents an attractive tool to investigate spatio-temporal behaviour of marine fish and has recently been suggested for monitoring underwater animal interactions.

Risky business for a juvenile marine predator? Testing the influence of foraging strategies on size and growth rate under natural conditions.

Mechanisms driving selection of body size and growth rate in wild marine vertebrates are poorly understood, thus limiting knowledge of their fitness costs at ecological, physiological and genetic scales. Here, we indirectly tested whether selection for size-related traits of juvenile sharks that inhabit a nursery hosting two dichotomous habitats, protected mangroves (low predation risk) and exposed seagrass beds (high predation risk), is influenced by their foraging behaviour. Juvenile sharks displayed a continuum of foraging strategies between mangrove and seagrass areas, with some individuals preferentially feeding in one habitat over another.

Learning and memory in the Port Jackson shark, Heterodontus portusjacksoni.

Basic understanding of the fundamental principles and mechanisms involved in learning is lacking for elasmobranch fishes. Our aim in this study was to experimentally investigate the learning and memory capacity of juvenile Port Jackson sharks, Heterodontus portusjacksoni. Sharks (N = 30) were conditioned over a 19-day period to associate an underwater LED light or stream of air-bubbles [conditioned stimulus (CS)] with a food reward [unconditioned stimulus (US)], using three procedures (delay, trace and control).