ORCID Profile
0000-0001-7680-8960
Current Organisations
University of Western Australia
,
Murdoch University
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Publisher: Springer Science and Business Media LLC
Date: 06-2015
Publisher: Wiley
Date: 2016
DOI: 10.1111/REC.12328
Publisher: Frontiers Media SA
Date: 17-12-2018
Publisher: Southern African Wildlife Management Association
Date: 10-2012
DOI: 10.3957/056.042.0210
Publisher: Springer Science and Business Media LLC
Date: 19-06-2021
DOI: 10.1007/S00227-021-03916-W
Abstract: Underwater visual surveys represent an essential component of coastal marine research and play a crucial role in supporting the management of marine systems. However, logistical and financial considerations can limit the availability of survey data in some systems. While biologging camera tag devices are being attached to an increasing ersity of marine animals to collect behavioral information about the focal species, the ancillary imagery collected can also be used in analytical techniques developed for er-based surveys. We illustrate this approach by extracting ancillary data from shark-borne camera tag deployments focused on the behavior of a White shark ( Carcharodon carcharias) off Gansbaai, South Africa, and a Grey Reef shark ( Carcharhinus amblyrhynchos) within the Chagos Archipelago. Within the giant kelp forest environment of Gansbaai we could determine the spatial density of kelp thali and underlying substrate composition. Within the coral reef environment, the animal-borne video allowed us to determine the approximate percent and type of benthic cover, as well as growth form and genus of corals down to the upper mesophotic zone. We also enumerated fish species-level abundance over reef flat and wall environments. We used established e-survey methods to analyze video data and found the results to be broadly comparable in the two systems studied. Our work illustrates the broad applicability of ancillary animal-borne video data, which is analogous in type and quality to er-based video data, for analysis in established marine community survey frameworks. As camera tags and associated biologging technologies continue to develop and are adapted to new environments, utilising these data could have wide-ranging applications and could maximise the overall cost–benefit ratio within biologging deployments.
Publisher: Wiley
Date: 12-02-2021
DOI: 10.1002/ECY.3251
Publisher: Springer Science and Business Media LLC
Date: 23-08-2019
Publisher: Springer Science and Business Media LLC
Date: 06-2013
DOI: 10.1038/S41586-019-1444-4
Abstract: 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. Space-use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively), and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). Our results demonstrate an urgent need for conservation and management measures at high-seas hotspots of shark space use, and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real-time, dynamic management.
Publisher: The Royal Society
Date: 04-2019
Abstract: Traditional forms of marine wildlife research are often restricted to coarse telemetry or surface-based observations, limiting information on fine-scale behaviours such as predator–prey events and interactions with habitat features. We use contemporary animal-attached cameras with motion sensing dataloggers, to reveal novel behaviours by white sharks, Carcharodon carcharias , within areas of kelp forest in South Africa. All white sharks tagged in this study spent time adjacent to kelp forests, with several moving throughout densely kelp-covered areas, navigating through channels and pushing directly through stipes and fronds. We found that activity and turning rates significantly increased within kelp forest. Over 28 h of video data revealed that white shark encounters with Cape fur seals, Arctocephalus pusillus pusillus , occurred exclusively within kelp forests, with seals displaying predator evasion behaviour during those encounters. Uniquely, we reveal the use of kelp forest habitat by white sharks, previously assumed inaccessible to these large predators.
Publisher: Inter-Research Science Center
Date: 23-06-2014
DOI: 10.3354/MEPS10814
Publisher: Public Library of Science (PLoS)
Date: 12-08-2013
Publisher: Wiley
Date: 18-01-2016
Publisher: Authorea, Inc.
Date: 08-05-2023
DOI: 10.22541/AU.168354208.81965128/V1
Abstract: An animal’s movement is influenced by a plethora of internal and external factors, leading to in idual- and habitat-specific movement characteristics. This plasticity is thought to allow in iduals to exploit erse environments efficiently. We tested if the movement characteristics of white sharks Carcharodon carcharias differ across ontogeny and among habitats along the coast of Central California. In doing so, we elucidate how changes in internal state (physiological changes coinciding with body size) and external environments (differing seascapes and/or diel phases) shape the movement of this globally distributed predator. White sharks, from small juveniles to large adults, were equipped with motion-sensitive biologging tags at four contrasting seascapes: two islands, a headland, and an inshore cove. From multi-sensor biologging data, 20 metrics characterising movement were derived and subjected to multivariate analyses. Movement characteristics were most different across seascapes, followed by ontogeny and diel phase. Juvenile sharks, that were only encountered at the cove, displayed the most distinct movement characteristics. Sharks at this seascape remained close to the shore and were comparatively less active than sub-adult and adult sharks tagged elsewhere. Distinct night-time movements and e patterns were recorded from sharks at an island seascape but not from those at the headland or inshore cove. The availability of prey and access to deeper water are likely drivers, with greater numbers of Northern elephant seals Mirounga angustirostris at the island seascapes and harbour seals Phoca vitulina at the headland seascape, while the offshore island group is also closer to the continental shelf edge. Juvenile sharks at the inshore cove are piscivorous and their habitat was not adjacent to pinniped haul out areas nor deeper water. This study demonstrates plasticity in the movements of a top predator, that adapts its routine to suit the habitat it forages within.
Publisher: Springer Science and Business Media LLC
Date: 07-07-2021
Publisher: Wiley
Date: 12-06-2023
DOI: 10.1111/JFB.15464
Abstract: Sharks are an important attraction for aquaria however, larger species can rarely be kept indefinitely. To date, there has been little work tracking shark movements post‐release to the wild. The authors used high‐resolution biologgers to monitor a sub‐adult tiger shark's pre‐ and post‐release fine‐scale movements following 2 years of captivity in an aquarium. They also compared its movement with that of a wild shark tagged nearby. Despite the differences in movement between the two sharks, with vertical oscillations notably absent and greater levels of turning seen from the released shark, the captive shark survived the release. These biologgers improve insight into post‐release movements of captive sharks.
Publisher: CRC Press
Date: 03-02-2012
DOI: 10.1201/B11532-8
Publisher: Frontiers Media SA
Date: 07-04-2022
DOI: 10.3389/FMARS.2022.811985
Abstract: Human activities in the oceans increase the extinction risk of marine megafauna. Interventions require an understanding of movement patterns and the spatiotemporal overlap with threats. We analysed the movement patterns of 33 white sharks ( Carcharodon carcharias ) satellite-tagged in South Africa between 2012 and 2014 to investigate the influence of size, sex and season on movement patterns and the spatial and temporal overlap with longline and gillnet fisheries and marine protected areas (MPAs). We used a hidden Markov model to identify ‘resident’ and ‘transient’ movement states and investigate the effect of covariates on the transition probabilities between states. A model with sex, total length and season had the most support. Tagged sharks were more likely to be in a resident state near the coast and a transient state away from the coast, while the probability of finding a shark in the transient state increased with size. White sharks moved across vast areas of the southwest Indian Ocean, emphasising the need for a regional management plan. White sharks overlapped with longline and gillnet fisheries within 25% of South Africa’s Exclusive Economic Zone and spent 15% of their time exposed to these fisheries during the study period. The demersal shark longline fishery had the highest relative spatial and temporal overlap, followed by the pelagic longline fishery and the KwaZulu-Natal (KZN) shark nets and drumlines. However, the KZN shark nets and drumlines reported the highest white shark catches, emphasising the need to combine shark movement and fishing effort with reliable catch records to assess risks to shark populations accurately. White shark exposure to shark nets and drumlines, by movement state, sex and maturity status, corresponded with the catch composition of the fishery, providing support for a meaningful exposure risk estimate. White sharks spent significantly more time in MPAs than expected by chance, likely due to increased prey abundance or less disturbance, suggesting that MPAs can benefit large, mobile marine megafauna. Conservation of white sharks in Southern Africa can be improved by implementing non-lethal solutions to beach safety, increasing the observer coverage in fisheries, and continued monitoring of movement patterns and existing and emerging threats.
Publisher: Springer Science and Business Media LLC
Date: 07-07-2021
Publisher: Springer Science and Business Media LLC
Date: 19-09-2013
Publisher: Public Library of Science (PLoS)
Date: 14-11-2011
Publisher: Public Library of Science (PLoS)
Date: 12-06-2013
No related grants have been discovered for Oliver Jewell.