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  • 1
    Online Resource
    Online Resource
    Long‐term satellite tracking reveals region‐specific movements of a large pelagic predator, the shortfin mako shark, in the western North Atlantic Ocean
    Wiley ; 2017
    In:  Journal of Applied Ecology Vol. 54, No. 6 ( 2017-12), p. 1765-1775
    Details
    In: Journal of Applied Ecology, Wiley, Vol. 54, No. 6 ( 2017-12), p. 1765-1775
    Abstract: The large‐scale and region‐specific movements of shortfin mako sharks underscore the need for close cooperation amongst western North Atlantic nations and implementation of regionally and seasonally specific management strategies. The movement patterns also provide baseline information, which could be used in spatially explicit stock assessment models. Identification of high‐use areas by shortfin mako sharks provides focal areas for quantifying interactions with fisheries. The high harvest rate observed in our fisheries‐independent tracking study raises questions about the true rate of fisheries mortality experienced by shortfin mako sharks, calling for a cautionary interpretation of past stock assessments used to determine management policy for this highly migratory species of conservation concern.
    Type of Medium: Online Resource
    ISSN: 0021-8901 , 1365-2664
    URL: Issue
    URL: Article
    DOI: 10.1111/jpe.2017.54.issue-6
    DOI: 10.1111/1365-2664.12852
    Language: English
    Publisher: Wiley
    Publication Date: 2017
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  • 2
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    Global population genetic dynamics of a highly migratory, apex predator shark
    Wiley ; 2016
    In:  Molecular Ecology Vol. 25, No. 21 ( 2016-11), p. 5312-5329
    Details
    In: Molecular Ecology, Wiley, Vol. 25, No. 21 ( 2016-11), p. 5312-5329
    Abstract: Knowledge of genetic connectivity dynamics in the world's large‐bodied, highly migratory, apex predator sharks across their global ranges is limited. One such species, the tiger shark ( Galeocerdo cuvier ), occurs worldwide in warm temperate and tropical waters, uses remarkably diverse habitats (nearshore to pelagic) and possesses a generalist diet that can structure marine ecosystems through top‐down processes. We investigated the phylogeography and the global population structure of this exploited, phylogenetically enigmatic shark by using 10 nuclear microsatellites ( n  =   380) and sequences from the mitochondrial control region ( CR , n  =   340) and cytochrome oxidase I gene ( n  =   100). All three marker classes showed the genetic differentiation between tiger sharks from the western Atlantic and Indo‐Pacific ocean basins (microsatellite F ST   〉  0.129; CR Φ ST   〉  0.497), the presence of North vs. southwestern Atlantic differentiation and the isolation of tiger sharks sampled from Hawaii from other surveyed locations. Furthermore, mitochondrial DNA revealed high levels of intraocean basin matrilineal population structure, suggesting female philopatry and sex‐biased gene flow. Coalescent‐ and genetic distance‐based estimates of divergence from CR sequences were largely congruent ( d corr  = 0.0015–0.0050), indicating a separation of Indo‐Pacific and western Atlantic tiger sharks 〈 1 million years ago. Mitochondrial haplotype relationships suggested that the western South Atlantic Ocean was likely a historical connection for interocean basin linkages via the dispersal around South Africa. Together, the results reveal unexpectedly high levels of population structure in a highly migratory, behaviourally generalist, cosmopolitan ocean predator, calling for management and conservation on smaller‐than‐anticipated spatial scales.
    Type of Medium: Online Resource
    ISSN: 0962-1083 , 1365-294X
    URL: Issue
    URL: Article
    DOI: 10.1111/mec.2016.25.issue-21
    DOI: 10.1111/mec.13845
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 2016
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  • 3
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    Targeted Catch‐and‐Release of Prohibited Sharks: Sand Tigers in Coastal Delaware Waters
    Wiley ; 2017
    In:  Fisheries Vol. 42, No. 5 ( 2017-05), p. 281-287
    Details
    In: Fisheries, Wiley, Vol. 42, No. 5 ( 2017-05), p. 281-287
    Abstract: The popularity of recreational shark fishing appears to be on the rise in recent years, with current policies often failing to address the direct targeting of protected species in this sector. Examination of catch trends from the past decade revealed that more than 66 million sharks were caught by recreational anglers along the U.S. eastern coast alone, including more than 1.2 million prohibited species. Using Sand Tigers Carcharias taurus captured by volunteer anglers as a case study to evaluate post‐release mortality, 33 individuals were fitted with external acoustic tags and passively tracked using an array of acoustic receivers. Although rates of internal hooking and gear retention were high (57% and 60%), short‐term post‐release mortality was relatively low (6%) and was heavily influenced by hook location and retention. Given the dramatic increase in the range and extent of recreational fishing targeting prohibited species, even relatively low mortality rates may still pose a significant threat to recovery.
    Type of Medium: Online Resource
    ISSN: 0363-2415 , 1548-8446
    URL: Article
    DOI: 10.1080/03632415.2017.1306974
    Language: English
    Publisher: Wiley
    Publication Date: 2017
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  • 4
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    Patrolling the border: Billfish exploit the hypoxic boundary created by the world's largest oxygen minimum zone
    Wiley ; 2023
    In:  Journal of Animal Ecology Vol. 92, No. 8 ( 2023-08), p. 1658-1671
    Details
    In: Journal of Animal Ecology, Wiley, Vol. 92, No. 8 ( 2023-08), p. 1658-1671
    Abstract: Pelagic predators must contend with low prey densities that are irregularly distributed and dynamic in space and time. Based on satellite imagery and telemetry data, many pelagic predators will concentrate horizontal movements on ephemeral surface fronts—gradients between water masses—because of enhanced local productivity and increased forage fish densities. Vertical fronts (e.g. thermoclines, oxyclines) can be spatially and temporally persistent, and aggregate lower trophic level and diel vertically migrating organisms due to sharp changes in temperature, water density or available oxygen. Thus, vertical fronts represent a stable and potentially energy rich habitat feature for diving pelagic predators but remain little explored in their capacity to enhance foraging opportunities. Here, we use a novel suite of high‐resolution biologging data, including in situ derived oxygen saturation and video, to document how two top predators in the pelagic ecosystem exploit the vertical fronts created by the oxygen minimum zone of the eastern tropical Pacific. Prey search behaviour was dependent on dive shape, and significantly increased near the thermocline and hypoxic boundary for blue marlin Makaira nigricans and sailfish Istiophorus platypterus , respectively. Further, we identify a behaviour not yet reported for pelagic predators, whereby the predator repeatedly dives below the thermocline and hypoxic boundary (and by extension, below the prey). We hypothesize this behaviour is used to ambush prey concentrated at the boundaries from below. We describe how habitat fronts created by low oxygen environments can influence pelagic ecosystems, which will become increasingly important to understand in the context of global change and expanding oxygen minimum zones. We anticipate that our findings are shared among many pelagic predators where strong vertical fronts occur, and additional high‐resolution tagging is warranted to confirm this.
    Type of Medium: Online Resource
    ISSN: 0021-8790 , 1365-2656
    URL: Issue
    URL: Article
    DOI: 10.1111/jane.v92.8
    DOI: 10.1111/1365-2656.13940
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 2023
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  • 5
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    Refuges and risks: Evaluating the benefits of an expanded MPA network for mobile apex predators
    Wiley ; 2018
    In:  Diversity and Distributions Vol. 24, No. 9 ( 2018-09), p. 1217-1230
    Details
    In: Diversity and Distributions, Wiley, Vol. 24, No. 9 ( 2018-09), p. 1217-1230
    Abstract: Concurrently, assessing the effectiveness of marine protected areas and evaluating the degree of risk from humans to key species provide valuable information that can be integrated into conservation management planning. Tiger sharks ( Galeocerdo cuvier ) are a wide‐ranging ecologically important species subject to various threats. The aim of this study was to identify “hotspots” of tiger shark habitat use in relation to protected areas and potential risks from fishing. Location Southwest Indian Ocean, east coast of South Africa and Mozambique. Methods Satellite tags were fitted to 26 tiger sharks. A subset of 19 sharks with an average period at liberty of 197 ( SD  = 110) days were analysed using hotspot analysis to identify areas of core habitat use. The spatial and temporal overlap of significant hotspots with current and planned marine protected areas as well as risks from fishing and culling was then calculated. Results There was a 5.97% spatial overlap between tiger shark hotspots and marine protected areas, which would increase significantly ( p   〈  .05) to 24.36% with the expansion of planned protected areas in South Africa and could be as high as 41.43% if Mozambique similarly expanded neighbouring protected area boundaries. Tiger sharks remained largely coastal, but only showed a spatial overlap of 5.12% with shark culling nets in South Africa. Only three sharks undertook open ocean migrations during which they were more likely to interact with longline fisheries in the region. Main conclusions This study demonstrates how spatial information can be used to assess the overlap between marine protected areas and the core habitats of top marine predators and highlights how congruent transnational conservation management can improve the effectiveness of protected areas. Core habitat use of marine apex predators may also be indicative of productive habitats, and therefore, predators such as tiger sharks could act as surrogate species for identifying key habitats to prioritize for conservation planning.
    Type of Medium: Online Resource
    ISSN: 1366-9516 , 1472-4642
    URL: Issue
    URL: Article
    DOI: 10.1111/ddi.2018.24.issue-9
    DOI: 10.1111/ddi.12758
    Language: English
    Publisher: Wiley
    Publication Date: 2018
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  • 6
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    First insights into the vertical habitat use of the whitespotted eagle ray Aetobatus narinari revealed by pop‐up satellite archival tags
    Wiley ; 2021
    In:  Journal of Fish Biology Vol. 98, No. 1 ( 2021-01), p. 89-101
    Details
    In: Journal of Fish Biology, Wiley, Vol. 98, No. 1 ( 2021-01), p. 89-101
    Abstract: The whitespotted eagle ray Aetobatus narinari is a tropical to warm‐temperate benthopelagic batoid that ranges widely throughout the western Atlantic Ocean. Despite conservation concerns for the species, its vertical habitat use and diving behaviour remain unknown. Patterns and drivers in the depth distribution of A. narinari were investigated at two separate locations, the western North Atlantic (Islands of Bermuda) and the eastern Gulf of Mexico (Sarasota, Florida, U.S.A.). Between 2010 and 2014, seven pop‐up satellite archival tags were attached to A. narinari using three methods: a through‐tail suture, an external tail‐band and through‐wing attachment. Retention time ranged from 0 to 180 days, with tags attached via the through‐tail method retained longest. Tagged rays spent the majority of time (82.85 ± 12.17% S.D.) within the upper 10 m of the water column and, with one exception, no rays travelled deeper than ~26 m. One Bermuda ray recorded a maximum depth of 50.5 m, suggesting that these animals make excursions off the fore‐reef slope of the Bermuda Platform. Individuals occupied deeper depths (7.42 ± 3.99 m S.D.) during the day versus night (4.90 ± 2.89 m S.D.), which may be explained by foraging and/or predator avoidance. Each individual experienced a significant difference in depth and temperature distributions over the diel cycle. There was evidence that mean hourly depth was best described by location and individual variation using a generalized additive mixed model approach. This is the first study to compare depth distributions of A. narinari from different locations and describe the thermal habitat for this species. Our study highlights the importance of region in describing A. narinari depth use, which may be relevant when developing management plans, whilst demonstrating that diel patterns appear to hold across individuals.
    Type of Medium: Online Resource
    ISSN: 0022-1112 , 1095-8649
    URL: Issue
    URL: Article
    DOI: 10.1111/jfb.v98.1
    DOI: 10.1111/jfb.14560
    Language: English
    Publisher: Wiley
    Publication Date: 2021
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  • 7
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    Behavioral response of a mobile marine predator to environmental variables differs across ecoregions
    Wiley ; 2019
    In:  Ecography Vol. 42, No. 9 ( 2019-09), p. 1569-1578
    Details
    In: Ecography, Wiley, Vol. 42, No. 9 ( 2019-09), p. 1569-1578
    Abstract: Animal movement and habitat selection are in part a response to landscape heterogeneity. Many studies of movement and habitat selection necessarily use environmental covariates that are readily available over large‐scales, which are assumed representative of functional habitat features such as resource availability. For widely distributed species, response to such covariates may not be consistent across ecosystems, as response to any specific covariate is driven by its biological relevance within the context of each ecosystem. Thus, the study of any widely distributed species within a limited geographic region may provide inferences that are not widely generalizable. Our goal was to evaluate the response of a marine predator to a suite of environmental covariates across a wide ecological gradient. We identified two behavioral states (resident and transient) in the movements of shortfin mako sharks Isurus oxyrinchus tracked via satellite telemetry in two regions of the western North Atlantic Ocean: the tropical Caribbean/Gulf of Mexico marginal sea (CGM), and the temperate waters of the open western Atlantic Ocean (OWA). We compared patterns of resident behavior between regions, and modeled relationships between oceanographic variables and resident behavior. We tracked 39 sharks during 2013–2015. Resident behavior was associated with shallow, continental shelf and slope waters in both regions. In the OWA resident behavior was associated with low sea surface temperature and high primary productivity, however, sharks exhibited no response to either variable in the CGM. There was a negative relationship between sea‐surface height gradient (a proxy for oceanic fronts) and resident behavior in the OWA, and a positive relationship in the CGM. Our observations likely reflect shark responses to regional variability in factors responsible for the distribution and availability of prey. Our study illustrates the importance of studying widely distributed species in a consistent manner over large spatial scales.
    Type of Medium: Online Resource
    ISSN: 0906-7590 , 1600-0587
    URL: Issue
    URL: Article
    DOI: 10.1111/ecog.2019.v42.i9
    DOI: 10.1111/ecog.04463
    Language: English
    Publisher: Wiley
    Publication Date: 2019
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  • 8
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    Baseline Health and Nutritional Parameters of Wild Sand Tigers Sampled in Delaware Bay
    Wiley ; 2022
    In:  Journal of Aquatic Animal Health Vol. 34, No. 3 ( 2022-09), p. 101-115
    Details
    In: Journal of Aquatic Animal Health, Wiley, Vol. 34, No. 3 ( 2022-09), p. 101-115
    Abstract: Species‐specific hematological reference values are essential for diagnosis and treatment of disease and maintaining overall health of animals. This information is lacking for many species of elasmobranchs maintained in zoos and aquaria, thus reducing the effectiveness of care for these animals. Descriptive statistics and reference intervals were calculated for hematocrit and complete blood cell counts, biochemistry and protein electrophoresis parameters, trace minerals, vitamins, heavy metals, reproductive hormones, and fatty acids in the blood of 153 wild Sand Tigers Carcharias taurus of both sexes and a range of sizes caught in Delaware Bay (Delaware, USA). Mean hematocrit, total white blood cell counts, lymphocyte differentials, glucose, phosphorus, amylase, and aspartate aminotransferase levels were significantly higher in juveniles than in adults. Levels of estradiol, progesterone, testosterone, and differences in selenium and eicosapentaenoic acid (a polyunsaturated fatty acid) between males and females suggest that they are important parameters for improving Sand Tiger breeding success in managed care. Finally, blood metal levels for arsenic, cadmium, lead, and mercury suggest low levels of contaminant exposure for Sand Tigers during their summer residence in Delaware Bay. The results of this study provide baseline health parameters for wild Sand Tigers that will aid in effective maintenance of aquarium animals and contribute to a greater understanding of the biology of these sharks and efforts to accomplish sustainable management of their populations.
    Type of Medium: Online Resource
    ISSN: 0899-7659 , 1548-8667
    URL: Issue
    URL: Article
    DOI: 10.1002/aah.v34.3
    DOI: 10.1002/aah.10156
    Language: English
    Publisher: Wiley
    Publication Date: 2022
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  • 9
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    X-Radiographic Observations of Food Passage through Digestive Tracts of Lemon Sharks
    Wiley ; 1987
    In:  Transactions of the American Fisheries Society Vol. 116, No. 5 ( 1987-09), p. 763-767
    Details
    In: Transactions of the American Fisheries Society, Wiley, Vol. 116, No. 5 ( 1987-09), p. 763-767
    Type of Medium: Online Resource
    ISSN: 0002-8487 , 1548-8659
    URL: Article
    DOI: 10.1577/1548-8659(1987)116〈763:XOOFPT〉2.0.CO;2
    Language: English
    Publisher: Wiley
    Publication Date: 1987
    detail.hit.zdb_id: 2192460-0
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  • 10
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    Intraspecific variation in vertical habitat use by tiger sharks ( Galeocerdo cuvier ) in the western N orth A tlantic
    Wiley ; 2014
    In:  Ecology and Evolution Vol. 4, No. 10 ( 2014-05), p. 1768-1786
    Details
    In: Ecology and Evolution, Wiley, Vol. 4, No. 10 ( 2014-05), p. 1768-1786
    Abstract: Tiger sharks ( Galeocerdo cuvier ) are a wide ranging, potentially keystone predator species that display a variety of horizontal movement patterns, making use of coastal and pelagic waters. Far less, however, is known about their vertical movements and use of the water column. We used pop‐up satellite archival tags with two data sampling rates (high rate and standard rate tags) to investigate the vertical habitat use and diving behavior of tiger sharks tagged on the Puerto Rico–Virgin Islands platform and off Bermuda between 2008 and 2009. Useable data were received from nine of 14 sharks tagged, tracked over a total of 529 days. Sharks spent the majority of their time making yo‐yo dives within the upper 50 m of the water column and considerable time within the upper 5 m of the water column. As a result, sharks typically occupied a narrow daily temperature range (~2°C). Dives to greater than 200 m were common, and all sharks made dives to at least 250 m, with one shark reaching a depth of 828 m. Despite some similarities among individuals, a great deal of intraspecific variability in vertical habit use was observed. Four distinct depth distributions that were not related to tagging location, horizontal movements, sex, or size were detected. In addition, similar depth distributions did not necessitate similar dive patterns among sharks. Recognition of intraspecific variability in habitat use of top predators can be crucial for effective management of these species and for understanding their influence on ecosystem dynamics.
    Type of Medium: Online Resource
    ISSN: 2045-7758 , 2045-7758
    URL: Issue
    URL: Article
    DOI: 10.1002/ece3.2014.4.issue-10
    DOI: 10.1002/ece3.1053
    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 2635675-2
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