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Le Croizier G, Hoyos-Padilla M, Amezcua-Martínez F, Aquino-Baleytó M, Besnard L, Le Grand F, Le Loc'h F, Mathieu-Resuge M, Munaron JM, Ory A, Sardenne F, Schaal G, Lorrain A. Can biochemical tracers reveal ontogenetic trophic shift and individual prey selection in white sharks from Guadalupe Island, Northeast Pacific? ENVIRONMENTAL RESEARCH 2024:119507. [PMID: 38944105 DOI: 10.1016/j.envres.2024.119507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 06/26/2024] [Accepted: 06/27/2024] [Indexed: 07/01/2024]
Abstract
Refining the role of apex predators in marine food webs is a necessary step in predicting the consequences of their global decline under the footprint of fishing activities. White sharks (Carcharodon carcharias) are vulnerable predators, performing large migrations and able to forage on a variety of prey in different habitats. In the Northeast Pacific, juvenile and adult white sharks are found seasonally at the same aggregation sites, such as Guadalupe Island off Mexico. While adults are thought to target local pinniped colonies, very few prey-predator interactions have been documented and the diet of juveniles in this area remains poorly understood. Here we used carbon/nitrogen stable isotopes and fatty acids to characterize the trophic ecology of white sharks at Guadalupe Island. In contrast to the ontogenetic trophic shift paradigm, we detected no influence of size on muscle stable isotope and fatty acid composition, revealing no significant dietary variation between juvenile and adult sharks. Stable isotopes did not allow definitive conclusions to be drawn regarding the diet of white sharks at Guadalupe Island, due to significant variability in the contribution of different potential prey depending on the trophic discrimination factors used. However, most sharks were rich in polyunsaturated fatty acids (such as long-chain omega 3), suggesting a local diet of mainly pelagic prey (potentially large fish or cephalopods). A few individuals appeared to show recent consumption of pinnipeds, with higher proportions of saturated and monounsaturated fatty acids. These individual differences in fatty acid composition could reflect an ecological trade-off between consumption of prey rich in fat (marine mammals) versus prey rich in polyunsaturated fatty acids (pelagic prey), respectively meeting the energetic and physiological needs of white sharks. Although ontogenetic trophic changes were not able to be discerned, our results thus provide new insights into the physiological drivers of predator-prey interactions, which can benefit the definition of conservation strategies in a changing ocean.
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Affiliation(s)
- Gaël Le Croizier
- Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France.
| | - Mauricio Hoyos-Padilla
- Pelagios-Kakunjá A.C. Sinaloa 1540. Col. Las Garzas. C.P. 23070. La Paz, B.C.S., México; Fins Attached: Marine Research and Conservation 19675 Still Glen Drive Colorado Springs, CO 80908, USA.
| | - Felipe Amezcua-Martínez
- Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México. Av. Joel Montes Camarena S/N. Mazatlán, Sin. México, 82040
| | - Marc Aquino-Baleytó
- Pelagios-Kakunjá A.C. Sinaloa 1540. Col. Las Garzas. C.P. 23070. La Paz, B.C.S., México
| | - Lucien Besnard
- Division of Environmental Science and Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang 37673, South Korea
| | | | | | | | | | - Arthur Ory
- Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
| | - Fany Sardenne
- Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
| | - Gauthier Schaal
- Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
| | - Anne Lorrain
- Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
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2
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Raoult V, Phillips AA, Nelson J, Niella Y, Skinner C, Tilcock MB, Burke PJ, Szpak P, James WR, Harrod C. Why aquatic scientists should use sulfur stable isotope ratios (ẟ 34S) more often. CHEMOSPHERE 2024; 355:141816. [PMID: 38556184 DOI: 10.1016/j.chemosphere.2024.141816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 02/26/2024] [Accepted: 03/25/2024] [Indexed: 04/02/2024]
Abstract
Over the last few decades, measurements of light stable isotope ratios have been increasingly used to answer questions across physiology, biology, ecology, and archaeology. The vast majority analyse carbon (δ13C) and nitrogen (δ15N) stable isotopes as the 'default' isotopes, omitting sulfur (δ34S) due to time, cost, or perceived lack of benefits and instrumentation capabilities. Using just carbon and nitrogen isotopic ratios can produce results that are inconclusive, uncertain, or in the worst cases, even misleading, especially for scientists that are new to the use and interpretation of stable isotope data. Using sulfur isotope values more regularly has the potential to mitigate these issues, especially given recent advancements that have lowered measurement barriers. Here we provide a review documenting case studies with real-world data, re-analysing different biological topics (i.e. niche, physiology, diet, movement and bioarchaeology) with and without sulfur isotopes to highlight the various strengths of this stable isotope for various applications. We also include a preliminary meta-analysis of the trophic discrimination factor (TDF) for sulfur isotopes, which suggest small (mean -0.4 ± 1.7 ‰ SD) but taxa-dependent mean trophic discrimination. Each case study demonstrates how the exclusion of sulfur comes at the detriment of the results, often leading to very different outputs, or missing valuable discoveries entirely. Given that studies relying on carbon and nitrogen stable isotopes currently underpin most of our understanding of various ecological processes, this has concerning implications. Collectively, these examples strongly suggest that researchers planning to use carbon and nitrogen stable isotopes for their research should incorporate sulfur where possible, and that the new 'default' isotope systems for aquatic science should now be carbon, nitrogen, and sulfur.
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Affiliation(s)
- Vincent Raoult
- Blue Carbon Lab, School of Life and Environmental Science, Deakin University, VIC, Australia; Marine Ecology Group, School of Natural Sciences, Macquarie University, NSW, Australia.
| | - Alexandra A Phillips
- National Center for Ecological Analysis and Synthesis, University of California Santa Barbara, Santa Barbara, CA, USA
| | - James Nelson
- Department of Marine Science, University of Georgia, Athens, GA, USA
| | - Yuri Niella
- Marine Ecology Group, School of Natural Sciences, Macquarie University, NSW, Australia
| | - Christina Skinner
- Marine Spatial Ecology Lab, School of Biological Sciences, University of Queensland, QLD, Australia
| | | | - Patrick J Burke
- Marine Ecology Group, School of Natural Sciences, Macquarie University, NSW, Australia
| | - Paul Szpak
- Department of Anthropology, Trent University, Peterborough, Ontario, Canada
| | - W Ryan James
- Institute of Environment, Florida International University, Miami, FL, USA
| | - Chris Harrod
- Instituto Ciencias Naturales Alexander von Humboldt, Universidad de Antofagasta, Antofagasta, Chile; Millennium Nucleus INVASAL, Concepción, Chile; Universidad de Antofagasta Stable Isotope Facility, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
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3
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Pini-Fitzsimmons J, Raoult V, Gaston T, Knott NA, Brown C. Diving into the diet of provisioned smooth stingrays using stable isotope analysis. JOURNAL OF FISH BIOLOGY 2023; 102:1206-1218. [PMID: 36880179 DOI: 10.1111/jfb.15370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Accepted: 03/02/2023] [Indexed: 05/13/2023]
Abstract
Recreational fishing waste, produced from processing catches at shore-based fish cleaning facilities and discarded into adjacent waters, is foraged by various aquatic species. However, the potential alterations to the diet of consumers of these resources are poorly studied. Smooth stingrays (Bathytoshia brevicaudata) are a large demersal mesopredatory ray species and common scavenger of recreational fishing discards around southern Australia. Due to their attraction to fish cleaning sites, they are also common targets of unregulated 'stingray feeding' tourism where they are fed commercially produced baits (e.g., pilchards). This study provides a preliminary assessment of the diet of smooth stingrays provisioned recreational fishing discards and baits at two sites in southern New South Wales, Australia (Discard Site: recreational fishing discards only; Provisioning Site: recreational fishing discards and commercial baits) using stable isotope analysis of carbon (δ13 C) and nitrogen (δ15 N), and Bayesian stable isotope mixing models. Our results indicate that at both sites invertebrates, considered a main part of the natural diet of smooth stingrays, made a limited contribution to the diets of provisioned stingrays, while a benthic teleost fish that is a common recreational catch was the dominant contributor. As the assessed teleost is potentially a natural prey item for smooth stingrays, it remains unclear whether the contribution came from recreational fishing discards or natural foraging. However, due to smooth stingrays' typically opportunistic foraging strategy, we expected a greater mixture of resources from low to high trophic level prey than was observed. These results suggest that smooth stingrays have either lower reliance on invertebrates as a result of utilizing provisioned resources or higher reliance on teleost fishes than previously thought. Commercial bait products fed to stingrays at the Provisioning Site were not a major contributor to the diets of smooth stingrays, suggesting this activity has a low impact on their nutrition.
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Affiliation(s)
| | - Vincent Raoult
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW, Australia
| | - Troy Gaston
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW, Australia
| | - Nathan A Knott
- Marine Ecosystems Unit, Fisheries Research, New South Wales Department of Primary Industries, Huskisson, NSW, Australia
| | - Culum Brown
- School of Natural Sciences, Macquarie University, North Ryde, NSW, Australia
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4
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Grainger R, Raoult V, Peddemors VM, Machovsky-Capuska GE, Gaston TF, Raubenheimer D. Integrating isotopic and nutritional niches reveals multiple dimensions of individual diet specialisation in a marine apex predator. J Anim Ecol 2023; 92:514-534. [PMID: 36421071 PMCID: PMC10107186 DOI: 10.1111/1365-2656.13852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 09/23/2022] [Indexed: 11/27/2022]
Abstract
Dietary specialisations are important determinants of ecological structure, particularly in species with high per-capita trophic influence like marine apex predators. These species are, however, among the most challenging in which to establish spatiotemporally integrated diets. We introduce a novel integration of stable isotopes with a multidimensional nutritional niche framework that addresses the challenges of establishing spatiotemporally integrated nutritional niches in wild populations, and apply the framework to explore individual diet specialisation in a marine apex predator, the white shark Carcharodon carcharias. Sequential tooth files were sampled from juvenile white sharks to establish individual isotopic (δ-space; δ13 C, δ15 N, δ34 S) niche specialisation. Bayesian mixing models were then used to reveal individual-level prey (p-space) specialisation, and further combined with nutritional geometry models to quantify the nutritional (N-space) dimensions of individual specialisation, and their relationships to prey use. Isotopic and mixing model analyses indicated juvenile white sharks as individual specialists within a broader, generalist, population niche. Individual sharks differed in their consumption of several important mesopredator species, which suggested among-individual variance in trophic roles in either pelagic or benthic food webs. However, variation in nutrient intakes was small and not consistently correlated with differences in prey use, suggesting white sharks as nutritional specialists and that individuals could use functionally and nutritionally different prey as complementary means to achieve a common nutritional goal. We identify how degrees of individual specialisation can differ between niche spaces (δ-, p- or N-space), the physiological and ecological implications of this, and argue that integrating nutrition can provide stronger, mechanistic links between diet specialisation and its intrinsic (fitness/performance) and extrinsic (ecological) outcomes. Our time-integrated framework is adaptable for examining the nutritional consequences and drivers of food use variation at the individual, population or species level.
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Affiliation(s)
- Richard Grainger
- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Vincent Raoult
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, New South Wales, Australia
| | - Victor M Peddemors
- New South Wales Department of Primary Industries, Fisheries, Sydney Institute of Marine Science, Mosman, New South Wales, Australia
| | - Gabriel E Machovsky-Capuska
- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,Nutri Lens, East Ryde, New South Wales, Australia
| | - Troy F Gaston
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, New South Wales, Australia
| | - David Raubenheimer
- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia.,School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
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Séguigne C, Mourier J, Clua É, Buray N, Planes S. Citizen science provides valuable data to evaluate elasmobranch diversity and trends throughout the French Polynesia's shark sanctuary. PLoS One 2023; 18:e0282837. [PMID: 36947523 PMCID: PMC10032523 DOI: 10.1371/journal.pone.0282837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 02/23/2023] [Indexed: 03/23/2023] Open
Abstract
Observers of the Polynesian Shark Observatory (ORP), a citizen science network organized mainly through the Polynesian dive centers, collected an unprecedented amount of data from more than 13,916 dives spanning 43% of the islands of French Polynesia between July 8, 2011, and April 11, 2018. The objective for this type of data collection, which is not accessible within the standard research context, was to provide a unique dataset, and the opportunity to explore the specific diversity, distribution, seasonality and abundance of many elasmobranch species spread out throughout the territory of French Polynesia. Since the data are based on random citizen observations, the spatial distribution was biased toward the most frequented sites and islands where scuba diving is most developed. Overall, the increase in observed abundance of rays and sharks observed in French Polynesia, and the three most sampled islands as well as the high specific diversity recorded for the region, provide first evidence on the effectiveness of the French Polynesia's Shark Sanctuary, established in 2006. These data, collected randomly by the volunteers, also provide insights into potential movement patterns and site fidelity of some of the more commonly observed species. While no final conclusions can be drawn, it is clear that the network of volunteers that regularly contributes information to the Polynesian Shark Observatory plays a very important role in the delivery of much needed data for conservation and management action, as well as providing perspectives for new directions in research on sharks and rays in French Polynesia.
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Affiliation(s)
- Clémentine Séguigne
- PSL Université Paris: EPHE-UPVD-CNRS, USR 3278 CRIOBE BP 1013, Papetoai, Moorea, French Polynesia
- Laboratoire d'Excellence "CORAIL", Moorea, French Polynesia
| | - Johann Mourier
- Observatoire des Requins de Polynésie, Temae, Moorea, French Polynesia
- MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Sète, France
| | - Éric Clua
- PSL Université Paris: EPHE-UPVD-CNRS, USR 3278 CRIOBE BP 1013, Papetoai, Moorea, French Polynesia
- Laboratoire d'Excellence "CORAIL", Moorea, French Polynesia
- Observatoire des Requins de Polynésie, Temae, Moorea, French Polynesia
| | - Nicolas Buray
- Observatoire des Requins de Polynésie, Temae, Moorea, French Polynesia
| | - Serge Planes
- PSL Université Paris: EPHE-UPVD-CNRS, USR 3278 CRIOBE BP 1013, Papetoai, Moorea, French Polynesia
- Laboratoire d'Excellence "CORAIL", Moorea, French Polynesia
- Observatoire des Requins de Polynésie, Temae, Moorea, French Polynesia
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6
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Guttridge TL, Müller L, Keller BA, Bond ME, Grubbs RD, Winram W, Howey LA, Frazier BS, Gruber SH. Vertical space use and thermal range of the great hammerhead (Sphyrna mokarran), (Rüppell, 1837) in the western North Atlantic. JOURNAL OF FISH BIOLOGY 2022; 101:797-810. [PMID: 36056454 DOI: 10.1111/jfb.15185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 08/01/2022] [Indexed: 06/15/2023]
Abstract
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. Although conservation and management measures have yielded promising results in some regions, such as the United States, high levels of at-vessel and post-release mortality remain a major concern to the species population recovery. This examined the vertical space use and thermal range of pop-off archival satellite-tagged S. mokarran in the western North Atlantic Ocean, expanding the understanding of the ecological niche of this species and providing insight into by-catch mitigation strategies for fisheries managers. The results showed that S. mokarran predominantly used shallow depths (75% of records <30 m) and had a narrow temperature range (89% of records between 23 and 28°C). Individual differences in depth use were apparent, and a strong diel cycle was observed, with sharks occupying significantly deeper depths during the daytime. Furthermore, two individuals were confirmed pregnant with one migrating from the Bahamas to South Carolina, U.S.A., providing further evidence of regional connectivity and parturition off the U.S. East Coast. The findings suggest that S. mokarran may be vulnerable to incidental capture in the western North Atlantic commercial longline fisheries due to substantial vertical overlap between the species and the gear. The results can be incorporated into conservation and management efforts to develop and/or refine mitigation measures focused on reducing the by-catch and associated mortality of this species, which can ultimately aide S. mokarran population recovery in areas with poor conservation status.
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Affiliation(s)
- Tristan L Guttridge
- Saving the Blue, Cooper City, Florida, USA
- Bimini Biological Field Station Foundation, South Bimini, Bahamas
| | - Lukas Müller
- Marine Animal Ecology Group, Wageningen University, Wageningen, The Netherlands
- The Watermen Project, Geneva, Switzerland
| | - Bryan A Keller
- Saving the Blue, Cooper City, Florida, USA
- Coastal and Marine Laboratory, Florida State University, St. Teresa, Florida, USA
| | - Mark E Bond
- Department of Biological Sciences, Institute of Environment, Florida International University, North Miami, Florida, USA
| | - R Dean Grubbs
- South Carolina Department of Natural Resources, Marine Resources Research Institute, Charleston, South Carolina, USA
| | | | - Lucy A Howey
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Bryan S Frazier
- South Carolina Department of Natural Resources, Marine Resources Research Institute, Charleston, South Carolina, USA
| | - Samuel H Gruber
- Bimini Biological Field Station Foundation, South Bimini, Bahamas
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Riverón S, Raoult V, Slip DJ, Harcourt RG. Lipid extraction has tissue-dependent effects on isotopic values (δ 34 S, δ 13 C, and δ 15 N) from different marine predators. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2022; 36:e9346. [PMID: 35737589 PMCID: PMC9539579 DOI: 10.1002/rcm.9346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 05/31/2022] [Accepted: 06/22/2022] [Indexed: 06/15/2023]
Abstract
RATIONALE The use of sulfur isotopes to study trophic ecology in marine ecosystems has increased in the past decade. Unlike other commonly used isotopes (e.g., carbon), sulfur can better discriminate benthic and pelagic productivity. However, how lipid extraction affects sulfur isotopic values has not been assessed, despite its frequent use to remove lipid effects on δ13 C values. METHODS We used white muscle and liver samples from two species of sharks and skin samples from two species of pinnipeds (sea lion and fur seal) to assess the effects of lipid extraction on stable isotope values for δ34 S, δ13 C, and δ15 N. Isotopic values were determined using a continuous flow-isotope ratio mass spectrometer coupled to an elemental analyzer. RESULTS Lipid extraction significantly decreased δ34 S values in shark tissues, more so for liver than muscle (-4.6 ± 0.9‰ vs -0.8 ± 0.3‰, average change), with nearly no change in their standard deviations. Lipid extraction did not affect δ34 S values from pinniped skin samples (0.2 ± 0.8‰, average change). After lipid extraction, consistent increases in δ13 C values (0.2‰-7.3‰) were detected as expected, especially in tissue with high lipid content (C:N >4). After lipid extraction, significant increases in δ15 N values (0.5‰-1.4‰) were found in shark muscle and liver tissues. For pinniped skin samples, δ15 N values were not significantly lower after lipid extraction (-0.4‰ to -0.1‰). CONCLUSIONS Lipid extraction did not have a strong impact on δ34 S values of shark muscle and pinniped skin (≤1‰). However, our results suggest it is essential to consider the effects of lipid extraction when interpreting results from δ34 S values of shark liver tissue, as they significantly depleted values relative to bulk tissue (~5‰). This may reflect selective removal of sulfolipids and glutathione present in higher concentrations in the liver than in muscle and skin and requires further investigation.
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Affiliation(s)
- Sabrina Riverón
- Marine Predator Research Group, School of Natural SciencesMacquarie UniversitySydneyNew South WalesAustralia
| | - Vincent Raoult
- School of Environmental and Life SciencesUniversity of NewcastleOurimbahNew South WalesAustralia
- Marine Ecology GroupSchool of Natural SciencesMacquarie UniversitySydneyNew South WalesAustralia
| | - David J. Slip
- Marine Predator Research Group, School of Natural SciencesMacquarie UniversitySydneyNew South WalesAustralia
- Taronga Institute of Science and LearningTaronga Conservation Society AustraliaSydneyNew South WalesAustralia
| | - Robert G. Harcourt
- Marine Predator Research Group, School of Natural SciencesMacquarie UniversitySydneyNew South WalesAustralia
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8
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Chan AJ, Raoult V, Jaine FRA, Peddemors VM, Broadhurst MK, Williamson JE. Trophic niche of Australian cownose rays (Rhinoptera neglecta) and whitespotted eagle rays (Aetobatus ocellatus) along the east coast of Australia. JOURNAL OF FISH BIOLOGY 2022; 100:970-978. [PMID: 35225353 PMCID: PMC9310580 DOI: 10.1111/jfb.15028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 02/24/2022] [Accepted: 02/25/2022] [Indexed: 05/21/2023]
Abstract
Australian cownose rays (Rhinoptera neglecta) and whitespotted eagle rays (Aetobatus ocellatus) are large myliobatiform rays that co-occur off temperate eastern Australia. Here, we performed stable-isotope analyses (δ13 C, δ15 N and δ34 S) on fin clips of both species to gain insights into their trophic interactions and isotopic niches, and assess the effect of preservation (ethanol-stored versus frozen) on isotopic values of fin-clip tissue of R. neglecta. Linear mixed models identified species as the main factor contributing to variation among δ15 N and δ34 S values, and disc width for δ13 C. Bayesian ecological niche modelling indicated a 57.4% to 74.5% overlap of trophic niches, with the niche of R. neglecta being smaller and more constrained. Because values of δ13 C were similar between species, variation in isotopic niches were due to differences in δ15 N and δ34 S values. Linear mixed models failed to detect differences in isotopic values of ethanol-stored and frozen fin tissue of R. neglecta. This study provides the first examination of the trophic ecology of R. neglecta and the comparison of isotopic niche with A. ocellatus, which will facilitate future research into the trophic interactions of these species and aid better resource management.
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Affiliation(s)
- Alysha J. Chan
- School of Natural SciencesMacquarie UniversitySydneyNew South WalesAustralia
| | - Vincent Raoult
- School of Environmental and Life SciencesUniversity of NewcastleOurimbahNew South WalesAustralia
| | - Fabrice R. A. Jaine
- School of Natural SciencesMacquarie UniversitySydneyNew South WalesAustralia
- Sydney Institute of Marine ScienceMosmanNew South WalesAustralia
| | - Victor M. Peddemors
- New South Wales Department of Primary Industries, Fisheries ResearchSydney Institute of Marine ScienceMosmanNew South WalesAustralia
| | - Matt K. Broadhurst
- New South Wales Department of Primary Industries, Fisheries Conservation Technology Unit, National Marine Science CentreSouthern Cross UniversityCoffs HarbourNew South WalesAustralia
- Marine and Estuarine Ecology UnitSchool of Biological Sciences, University of QueenslandBrisbaneQueenslandAustralia
| | - Jane E. Williamson
- School of Natural SciencesMacquarie UniversitySydneyNew South WalesAustralia
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9
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Drivers of variation in occurrence, abundance, and behaviour of sharks on coral reefs. Sci Rep 2022; 12:728. [PMID: 35031666 PMCID: PMC8760336 DOI: 10.1038/s41598-021-04024-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 11/29/2021] [Indexed: 11/08/2022] Open
Abstract
Quantifying the drivers of population size in reef sharks is critical for the development of appropriate conservation strategies. In north-west Australia, shark populations inhabit coral reefs that border growing centres of human population, industry, and tourism. However, we lack baseline data on reef sharks at large spatial scales (hundreds of km) that might enable managers to assess the status of shark populations in the face of future development in this region. Here, we examined the occurrence, abundance and behaviour of apex (Galeocerdo cuvier, Carcharhinus plumbeus) and reef (C. amblyrhynchos, C. melanopterus, Triaenodon obesus) sharks using > 1200 deployments of baited remote underwater stereo-video systems (stereo-BRUVs) across > 500 km of coastline. We found evidence for species-specific influences of habitat and fishing activities on the occurrence (probability of observation), abundance (MaxN) and behaviour of sharks (time of arrival to the stereo-BRUVs and likelihood of feeding). Although the presence of management zoning (No-take areas) made little difference to most species, C. amblyrhynchos were more common further from boat ramps (a proxy of recreational fishing pressure). Time of arrival for all species was also influenced by distance to boat ramp, although patterns varied among species. Our results demonstrate the capacity for behavioural metrics to complement existing measures of occurrence and abundance in assessing the potential impact of human activities on shark populations.
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10
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Shen Y, Gong Y, Wu F, Li Y. Retrospective stable isotopes of vertebrae reveal sexual ontogenetic patterns and trophic ecology in oceanic whitetip shark, Carcharhinus longimanus. Ecol Evol 2022; 12:e8452. [PMID: 35127009 PMCID: PMC8796903 DOI: 10.1002/ece3.8452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 11/21/2021] [Accepted: 11/29/2021] [Indexed: 11/25/2022] Open
Abstract
There is a common phenomenon in nature whereby some animals have differences in their ontogenetic changes in dietary preferences between sexes, especially apex predators. These reflect changes in the needs of development during their lifetimes. Apex predators potentially have diverse dietary niches and a large impact on the trophic dynamics within ecosystems. However, the difference in life history between males and females often leads to increased difficulty in management and conservation. In this study, 25 oceanic whitetip sharks, Carcharhinus longimanus, were collected from the central and eastern tropical Pacific. Retrospective stable isotope analysis of vertebrae was used to evaluate the potential ontogenetic differences in feeding habits and niche width between sexes. Results showed that C. longimanus had a wide range of δ13C values (-18.1 to -12.3‰) and δ15N values (8.9-14.8‰). However, males and females had similar trophic positions with large niche overlap at similar growth stages. Both sexes had increasing δ13C values but relatively constant δ15N values along the vertebrae. These results indicated that male and female C. longimanus may share similar feeding strategies and movement patterns. The results presented in this study enhance our understanding of sexual ontogenetic patterns and ecological role of C. longimanus and highlighted the applicability of vertebrae for characterizing shark life-history traits.
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Affiliation(s)
- Yongfu Shen
- College of Marine SciencesShanghai Ocean UniversityShanghaiChina
| | - Yi Gong
- College of Marine SciencesShanghai Ocean UniversityShanghaiChina
- Laboratory for Marine Fisheries Science and Food Production ProcessesQingdao National Laboratory for Marine Science and TechnologyQingdaoChina
- The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries ResourcesMinistry of EducationShanghaiChina
- National Engineering Research Centre for Oceanic FisheriesShanghai Ocean UniversityShanghaiChina
| | - Feng Wu
- College of Marine SciencesShanghai Ocean UniversityShanghaiChina
- Laboratory for Marine Fisheries Science and Food Production ProcessesQingdao National Laboratory for Marine Science and TechnologyQingdaoChina
- The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries ResourcesMinistry of EducationShanghaiChina
- National Engineering Research Centre for Oceanic FisheriesShanghai Ocean UniversityShanghaiChina
| | - Yunkai Li
- College of Marine SciencesShanghai Ocean UniversityShanghaiChina
- Laboratory for Marine Fisheries Science and Food Production ProcessesQingdao National Laboratory for Marine Science and TechnologyQingdaoChina
- The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries ResourcesMinistry of EducationShanghaiChina
- National Engineering Research Centre for Oceanic FisheriesShanghai Ocean UniversityShanghaiChina
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11
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Hewitt DE, Taylor MD, Raoult V, Smith TM, Gaston TF. Diet-tissue discrimination and turnover of δ 13 C and δ 15 N in muscle tissue of a penaeid prawn. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2021; 35:e9167. [PMID: 34494325 DOI: 10.1002/rcm.9167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 07/13/2021] [Accepted: 07/16/2021] [Indexed: 06/13/2023]
Abstract
RATIONALE Stable isotopes are used to study trophic and movement ecology in aquatic systems, as they provide spatially distinct, time-integrated signatures of diet. Stable isotope ecology has been used to quantify species-habitat relationships in many important fisheries species (e.g., penaeid prawns), with approaches that typically assume constant values for diet-tissue discrimination and diet-tissue steady state, but these can be highly variable. Here we provide the first report of these processes in Metapenaeus macleayi (eastern school prawn). METHODS Here we explicitly measure and model carbon (δ13 C) and nitrogen (δ15 N) diet-tissue discrimination and turnover in eastern school prawn muscle tissue as a function of experimental time following a change in diet to an isotopically distinct food source. RESULTS Diet-tissue discrimination factors were 5 and 0.6‰ for δ13 C and δ15 N, respectively. Prawn muscle tissue reached an approximate steady state after approximately 50 and 30 days for δ13 C and δ15 N. Half-lives indicated faster turnover of δ15 N (~8 days) than δ13 C (~14 days). CONCLUSIONS Our diet-tissue discrimination factors deviate from 'typical' values with larger values for carbon than nitrogen isotopes, but are generally similar to those measured in other crustaceans. Similarly, our estimates of isotopic turnover align with those in other penaeid species. These findings confirm muscle tissue as a reliable indicator of long-term diet and movement patterns in eastern school prawn.
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Affiliation(s)
- Daniel E Hewitt
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW, Australia
| | - Matthew D Taylor
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW, Australia
- New South Wales Department of Primary Industries, Port Stephens Fisheries Institute, Nelson Bay, NSW, Australia
| | - Vincent Raoult
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW, Australia
| | - Timothy M Smith
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW, Australia
- Centre for Tropical Water and Aquatic Ecosystems Research (TropWATER), James Cook University, Cairns, QLD, Australia
| | - Troy F Gaston
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW, Australia
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12
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Secondary predation constrains DNA-based diet reconstruction in two threatened shark species. Sci Rep 2021; 11:18350. [PMID: 34526519 PMCID: PMC8443726 DOI: 10.1038/s41598-021-96856-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 08/04/2021] [Indexed: 02/08/2023] Open
Abstract
Increasing fishing effort, including bycatch and discard practices, are impacting marine biodiversity, particularly among slow-to-reproduce taxa such as elasmobranchs, and specifically sharks. While some fisheries involving sharks are sustainably managed, collateral mortalities continue, contributing towards > 35% of species being threatened with extinction. To effectively manage shark stocks, life-history information, including resource use and feeding ecologies is pivotal, especially among those species with wide-ranging distributions. Two cosmopolitan sharks bycaught off eastern Australia are the common blacktip shark (Carcharhinus limbatus; globally classified as Near Threatened) and great hammerhead (Sphyrna mokarran; Critically Endangered). We opportunistically sampled the digestive tracts of these two species (and also any whole prey; termed the 'Russian-doll' approach), caught in bather-protection gillnets off northern New South Wales, to investigate the capacity for DNA metabarcoding to simultaneously determine predator and prey regional feeding ecologies. While sample sizes were small, S. mokkaran fed predominantly on stingrays and skates (Myliobatiformes and Rajiformes), but also teleosts, while C. limbatus mostly consumed teleosts. Metabarcoding assays showed extensive intermixing of taxa from the digestive tracts of predators and their whole prey, likely via the predator's stomach chyme, negating the opportunity to distinguish between primary and secondary predation. This Russian-doll effect requires further investigation in DNA metabarcoding studies focussing on dietary preferences and implies that any outcomes will need to be interpreted concomitant with traditional visual approaches.
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13
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Lear KO, Whitney NM, Morris JJ, Gleiss AC. Temporal niche partitioning as a novel mechanism promoting co-existence of sympatric predators in marine systems. Proc Biol Sci 2021; 288:20210816. [PMID: 34229487 PMCID: PMC8261200 DOI: 10.1098/rspb.2021.0816] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Niche partitioning of time, space or resources is considered the key to allowing the coexistence of competitor species, and particularly guilds of predators. However, the extent to which these processes occur in marine systems is poorly understood due to the difficulty in studying fine-scale movements and activity patterns in mobile underwater species. Here, we used acceleration data-loggers to investigate temporal partitioning in a guild of marine predators. Six species of co-occurring large coastal sharks demonstrated distinct diel patterns of activity, providing evidence of strong temporal partitioning of foraging times. This is the first instance of diel temporal niche partitioning described in a marine predator guild, and is probably driven by a combination of physiological constraints in diel timing of activity (e.g. sensory adaptations) and interference competition (hierarchical predation within the guild), which may force less dominant predators to suboptimal foraging times to avoid agonistic interactions. Temporal partitioning is often thought to be rare compared to other partitioning mechanisms, but the occurrence of temporal partitioning here and similar characteristics in many other marine ecosystems (multiple predators simultaneously present in the same space with dietary overlap) introduces the question of whether this is a common mechanism of resource division in marine systems.
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Affiliation(s)
- Karissa O Lear
- Centre for Sustainable Aquatic Ecosystems, Harry Butler Institute, Murdoch University, 90 South Street, Murdoch, Western Australia 6150, Australia
| | - Nicholas M Whitney
- Anderson Cabot Center for Ocean Life, New England Aquarium, 1 Central Wharf, Boston, MA 02110, USA
| | - John J Morris
- Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236, USA
| | - Adrian C Gleiss
- Centre for Sustainable Aquatic Ecosystems, Harry Butler Institute, Murdoch University, 90 South Street, Murdoch, Western Australia 6150, Australia.,Environmental and Conservation Sciences, Murdoch University, 90 South Street, Murdoch, Western Australia 6150, Australia
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14
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Riverón S, Raoult V, Baylis AMM, Jones KA, Slip DJ, Harcourt RG. Pelagic and benthic ecosystems drive differences in population and individual specializations in marine predators. Oecologia 2021; 196:891-904. [PMID: 34173892 DOI: 10.1007/s00442-021-04974-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 06/13/2021] [Indexed: 11/24/2022]
Abstract
Individual specialization, which describes whether populations are comprised of dietary generalists or specialists, has profound ecological and evolutionary implications. However, few studies have quantified individual specialization within and between sympatric species that are functionally similar but have different foraging modes. We assessed the relationship between individual specialization, isotopic niche metrics and foraging behaviour of two marine predators with contrasting foraging modes: pelagic foraging female South American fur seals (Arctocephalus australis) and benthic foraging female southern sea lions (Otaria byronia). Stable isotope analysis of carbon and nitrogen was conducted along the length of adult female vibrissae to determine isotopic niche metrics and the degree of individual specialization. Vibrissae integrated time ranged between 1.1 and 5.5 years, depending on vibrissae length. We found limited overlap in dietary niche-space. Broader population niche sizes were associated with higher degrees of individual specialization, while narrower population niches with lower degrees of individual specialization. The degree of individual specialization was influenced by pelagic and benthic foraging modes. Specifically, South American fur seals, foraging in dynamic pelagic environments with abundant but similar prey, comprised specialist populations composed of generalist individuals. In contrast, benthic southern sea lions foraging in habitats with diverse but less abundant prey had more generalist populations composed of highly specialized individuals. We hypothesize that differences in specialization within and between populations were related to prey availability and habitat differences. Our study supports growing body of literature highlighting that individual specialization is a critical factor in shaping the ecological niche of higher marine predators.
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Affiliation(s)
- Sabrina Riverón
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia.
| | - Vincent Raoult
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, Australia
| | - Alastair M M Baylis
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia.,South Atlantic Environmental Research Institute, Stanley Cottage, PO Box 609, Stanley, FIQQ 1ZZ, Falkland Islands
| | - Kayleigh A Jones
- British Antarctic Survey, High Cross, Madingley Rd, Cambridge, CB3 0ET, UK.,University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK
| | - David J Slip
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia.,Taronga Conservation Society Australia, Bradley's Head Road, Mosman, NSW, 2088, Australia
| | - Robert G Harcourt
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia
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15
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Niella Y, Raoult V, Gaston T, Peddemors VM, Harcourt R, Smoothey AF. Overcoming multi-year impacts of maternal isotope signatures using multi-tracers and fast turnover tissues in juvenile sharks. CHEMOSPHERE 2021; 269:129393. [PMID: 33383247 DOI: 10.1016/j.chemosphere.2020.129393] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 12/16/2020] [Accepted: 12/18/2020] [Indexed: 06/12/2023]
Abstract
Stable isotopes are often used to determine the ecological role of different age classes of animals, but particularly for young animals this approach may be compromised. During gestation and or incubation body tissues of the young are derived directly from the mother. In neonates or post hatching, there is a period of transformation as the young grow and forage independently, but during this period different organs will continue to reflect the maternal isotopic signature as a function of their turnover rate. How long this maternal hangover persists remains poorly understood. We applied a multi-tracer approach (δ15N, δ13C and δ34S) to stable isotope signatures in juvenile bull sharks (Carcharhinus leucas) up to 6.5 years post parturition. We found that maternal provisioning was detectable for up to 3.5 years after birth in muscle but only detectable in young-of-the-year for liver. Inclusion of sulphur revealed when maternal signatures disappeared from low-turnover tissue, while also identifying the spatial and trophic ecology patterns from fast-turnover tissue. These results reveal the importance of sampling fast turnover tissues to study the trophic ecology of juvenile elasmobranchs, and how the use of only δ15N and δ13C isotopes is likely to make maternal patterns more difficult to detect.
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Affiliation(s)
- Yuri Niella
- Department of Biological Sciences, Macquarie University, North Ryde, 2113, Sydney, New South Wales, Australia.
| | - Vincent Raoult
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, New South Wales, 2258, Australia
| | - Troy Gaston
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, New South Wales, 2258, Australia
| | - Victor M Peddemors
- NSW Department of Primary Industries, Fisheries Research, Sydney Institute of Marine Science, Mosman, 2088, Sydney, New South Wales, Australia
| | - Robert Harcourt
- Department of Biological Sciences, Macquarie University, North Ryde, 2113, Sydney, New South Wales, Australia
| | - Amy F Smoothey
- NSW Department of Primary Industries, Fisheries Research, Sydney Institute of Marine Science, Mosman, 2088, Sydney, New South Wales, Australia
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16
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Gervais CR, Brown C. Impact of conspecific necromones on the oxygen uptake rates of a benthic elasmobranch. Anim Behav 2021. [DOI: 10.1016/j.anbehav.2021.01.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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17
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Souza-Araujo J, Souza-Junior OG, Guimarães-Costa A, Hussey NE, Lima MO, Giarrizzo T. The consumption of shark meat in the Amazon region and its implications for human health and the marine ecosystem. CHEMOSPHERE 2021; 265:129132. [PMID: 33307506 DOI: 10.1016/j.chemosphere.2020.129132] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 11/23/2020] [Accepted: 11/25/2020] [Indexed: 06/12/2023]
Abstract
Here, we evaluated the levels of As, Hg, Pb, and Cd in shark meat sold along the Amazon Coast of Brazil and used nitrogen stable isotope values to determine trophic position and to assess element biomagnification. From market samples, a total of 13 species were identified via molecular analysis, including those listed as endangered and vulnerable by the IUCN Red List. Arsenic was present in significantly higher concentrations than all other elements, followed by Hg, with the highest mean concentrations recorded in M. higmani (As: 19.46 ± 8.79 μg/g ww) and C. acronotus (Hg: 1.12 ± 0.68 μg/g ww). Lead and Cd were recorded at much lower levels in all species. The EWI of individual elements were above PTWI for all species when considering Hg, seven species for inorganic arsenic (iAs), and one species for Pb. The weekly consumption of 10 species should be reduced to less than 416.39 g, which is equivalent to the daily estimated fish consumption rate in the region. The mean (±SD) δ15N values of species ranged from 10.7 ± 0.51‰ in M. higmani to 14.2 ± 0.59‰ in C. porosus, indicating feeding over >1 trophic level. Arsenic was negatively correlated with δ15N values, while Hg was positively correlated indicating biodilution and biomagnification, respectively. Our results indicate that the sale and consumption of shark meat will expose consumers to potentially harmful levels of iAs and Hg, as well as contributing to the population decline of species including those that are currently categorized as threatened.
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Affiliation(s)
- J Souza-Araujo
- Núcleo de Ecologia Aquática e Pesca da Amazônia, Universidade Federal Do Pará, Av. Perimetral 2651, 66040170, Belém, PA, Brazil.
| | - O G Souza-Junior
- Núcleo de Ecologia Aquática e Pesca da Amazônia, Universidade Federal Do Pará, Av. Perimetral 2651, 66040170, Belém, PA, Brazil.
| | - A Guimarães-Costa
- Instituto de Estudos Costeiros, Universidade Federal Do Pará, Alameda Leandro Ribeiro, 68600 - 000, Bragança, PA, Brazil.
| | - N E Hussey
- Integrative Biology, University of Windsor, Windsor, Ontario, N9B 3P4, Canada.
| | - M O Lima
- Instituto Evandro Chagas. Seção de Meio Ambiente. Rodovia BR-316, Km 7, S/N, 67030000, Ananindeua, PA, Brazil.
| | - T Giarrizzo
- Núcleo de Ecologia Aquática e Pesca da Amazônia, Universidade Federal Do Pará, Av. Perimetral 2651, 66040170, Belém, PA, Brazil.
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18
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Abstract
Over the past decade, drones have become a popular tool for wildlife management and research. Drones have shown significant value for animals that were often difficult or dangerous to study using traditional survey methods. In the past five years drone technology has become commonplace for shark research with their use above, and more recently, below the water helping to minimise knowledge gaps about these cryptic species. Drones have enhanced our understanding of shark behaviour and are critically important tools, not only due to the importance and conservation of the animals in the ecosystem, but to also help minimise dangerous encounters with humans. To provide some guidance for their future use in relation to sharks, this review provides an overview of how drones are currently used with critical context for shark monitoring. We show how drones have been used to fill knowledge gaps around fundamental shark behaviours or movements, social interactions, and predation across multiple species and scenarios. We further detail the advancement in technology across sensors, automation, and artificial intelligence that are improving our abilities in data collection and analysis and opening opportunities for shark-related beach safety. An investigation of the shark-based research potential for underwater drones (ROV/AUV) is also provided. Finally, this review provides baseline observations that have been pioneered for shark research and recommendations for how drones might be used to enhance our knowledge in the future.
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19
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Jorgensen SJ, Micheli F, White TD, Van Houtan KS, Alfaro-Shigueto J, Andrzejaczek S, Arnoldi NS, Baum JK, Block B, Britten GL, Butner C, Caballero S, Cardeñosa D, Chapple TK, Clarke S, Cortés E, Dulvy NK, Fowler S, Gallagher AJ, Gilman E, Godley BJ, Graham RT, Hammerschlag N, Harry AV, Heithaus M, Hutchinson M, Huveneers C, Lowe CG, Lucifora LO, MacKeracher T, Mangel JC, Barbosa Martins AP, McCauley DJ, McClenachan L, Mull C, Natanson LJ, Pauly D, Pazmiño DA, Pistevos JCA, Queiroz N, Roff G, Shea BD, Simpfendorfer CA, Sims DW, Ward-Paige C, Worm B, Ferretti F. Emergent research and priorities for shark and ray conservation. ENDANGER SPECIES RES 2021. [DOI: 10.3354/esr01169] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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20
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Burgess KB, Broadhurst MK, Raoult V, Laglbauer BJL, Coleman MA, Bennett MB. Short- and long-term diets of the threatened longhorned pygmy devil ray, Mobula eregoodoo determined using stable isotopes. JOURNAL OF FISH BIOLOGY 2020; 97:424-434. [PMID: 32415778 DOI: 10.1111/jfb.14381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 05/05/2020] [Accepted: 05/12/2020] [Indexed: 06/11/2023]
Abstract
Most mobulids are listed as near threatened to endangered. Nonetheless, effective conservation measures are hindered by knowledge gaps in their ecology and behaviour. In particular, few studies have assessed diets and trophic ecologies that could inform methods to avoid fishing mortality. Here, a shortfall in data for the longhorned pygmy devil ray, Mobula eregoodoo was addressed by describing temporal variability in dietary preferences using stable isotope analysis. During summer and autumn in 2017, five bather-protection gillnets were deployed off eastern Australia (29° S, 153.5° E). From the catches of these gillnets, 35 adult M. eregoodoo had liver, muscle and stomach contents sampled to determine δ13 C and δ15 N profiles. Analyses revealed that surface zooplankton and zooplanktivorous teleosts were important dietary components across short- and long-term temporal scales. Large quantities of undigested sandy sprat, Hyperlophus vittatus, in the stomachs of some specimens unequivocally confirm feeding on teleosts. A narrow isotopic niche and minimal isotopic overlap with reef manta rays, Mobula alfredi from the same geographic region in eastern Australia implies M. eregoodoo has unique and highly specialised resource use relative to other mobulids in the area. The species is clearly vulnerable to capture during inshore migrations, presumably where they feed on shallow-water shoaling teleosts. Female M. eregoodoo likely have a low annual reproductive output, so population recoveries from fishing-induced declines are likely to be slow. Measures to reduce the by catch of M. eregoodoo in local bather-protection gillnets, and artisanal fisheries more broadly, should be given priority.
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Affiliation(s)
- Katherine B Burgess
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Matt K Broadhurst
- New South Wales Government Department of Primary Industries, Fisheries Conservation Technology Unit, 2 Bay Drive, Charlesworth Bay, Coffs Harbour, Australia, Australia
- Marine and Estuarine Ecology Unit, School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Vincent Raoult
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, New South Wales, Australia
| | - Betty J L Laglbauer
- Department of Oceanography and Fisheries, University of the Azores, Horta, Portugal
| | - Melinda A Coleman
- Department of Primary Industries, New South Wales Fisheries, National Marine Science Centre, 2 Bay Drive, Coffs Harbour, NSW, 2450, Australia
| | - Michael B Bennett
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
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21
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Doan MD, Kajiura SM. Adult blacktip sharks (Carcharhinus limbatus) use shallow water as a refuge from great hammerheads (Sphyrna mokarran). JOURNAL OF FISH BIOLOGY 2020; 96:1530-1533. [PMID: 32274798 DOI: 10.1111/jfb.14342] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 04/03/2020] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
A refuge can be any space that keeps an organism safe from danger. Prey usually seek protection in the closest refuge available to minimize cost while maximizing survival. Aerial drone footage of blacktip sharks, Carcharhinus limbatus, along the coast of southeast Florida, USA, shows adult blacktips fleeing to the shallow water adjacent to the beach when confronted with or chased by a predatory great hammerhead shark, Sphyrna mokarran. To authors' knowledge, this is the first evidence of adult C. limbatus using shallow waters as a refuge.
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Affiliation(s)
- Melanie D Doan
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida, USA
| | - Stephen M Kajiura
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida, USA
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