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Christopher G Lowe - One of the best experts on this subject based on the ideXlab platform.
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An evaluation of body condition and morphometric relationships within southern California juvenile white sharks Carcharodon carcharias.
Journal of fish biology, 2018Co-Authors: Ryan K. Logan, Chuck Winkler, Christopher G Lowe, John O'sullivan, Connor F. White, Salvador J. Jorgensen, Kady LyonsAbstract:Length, mass and girth relationships are presented for 112 juvenile white sharks (JWS) Carcharodon carcharias caught in the Southern California Bight (SCB) nursery area between June 2008 and August 2017. No difference was found between male and female JWS length-mass relationships, but data suggest that JWS in the SCB gain more mass per unit length for the juvenile size classes compared with other C. carcharias populations. Condition-factor-to-liver-mass and condition-factor-to-liver-lipid-content relationships revealed that length and mass (i.e., condition factor) can be used as a non-invasive proxy for body condition for juveniles of this species. The parameters estimated in this study are key information for population assessments of juvenile C. carcharias in the north-east Pacific Ocean and will contribute to the conservation and management of this IUCN Red List Vulnerable species.
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effects of trophic ecology and habitat use on maternal transfer of contaminants in four species of young of the year lamniform sharks
Marine Environmental Research, 2013Co-Authors: Kady Lyons, Aaron B Carlisle, Antonella Preti, Christopher G Mull, Mary Ellen Blasius, John Osullivan, Chuck Winkler, Christopher G LoweAbstract:Organic contaminant and total mercury concentrations were compared in four species of lamniform sharks over several age classes to examine bioaccumulation patterns and gain insights into trophic ecology. Contaminants found in young of the year (YOY) sharks were assumed to be derived from maternal sources and used as a proxy to investigate factors that influence maternal offloading processes. YOY white (Carcharodon carcharias) and mako (Isurus oxyrinchus) sharks had comparable and significantly higher concentrations of PCBs, DDTs, pesticides, and mercury than YOY thresher (Alopias vulpinus) or salmon (Lamna ditropis) sharks. A significant positive relationship was found between YOY contaminant loads and maternal trophic position, suggesting that trophic ecology is one factor that plays an important role in maternal offloading. Differences in organic contaminant signatures and contaminant concentration magnitudes among species corroborated what is known about species habitat use and may be used to provide insights into the feeding ecology of these animals.
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observation of an attack by a cookiecutter shark isistius brasiliensis on a white shark Carcharodon carcharias
Pacific Science, 2013Co-Authors: Mauricio Hoyospadilla, John Osullivan, Yannis P. Papastamatiou, Christopher G LoweAbstract:Cookiecutter sharks (Isistius brasiliensis) are known to attack a wide array of large animals including pelagic fishes, cetaceans, and pinnipeds. Here we add another top predator, the white shark (Carcharodon carcharias), to the list of potential victims. A subadult male white shark off Guadelupe Island, Mexico, was observed with a fresh cookiecutter shark bite next to its mouth, as well as a second crescent-shaped scar. A subadult male white shark was tracked in the same location and showed diel changes in depth, with the shark occupying shallow water (<50 m) at night, which may be when white sharks overlap with the vertical distribution of cookiecutter sharks. This further indicates that the majority of co-occurring marine top predators can be targeted by cookiecutter sharks.
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Observation of an Attack by a Cookiecutter Shark (Isistius brasiliensis) on a White Shark (Carcharodon carcharias)
Pacific Science, 2013Co-Authors: Mauricio Hoyos-padilla, Yannis P. Papastamatiou, John O'sullivan, Christopher G LoweAbstract:Cookiecutter sharks (Isistius brasiliensis) are known to attack a wide array of large animals including pelagic fishes, cetaceans, and pinnipeds. Here we add another top predator, the white shark (Carcharodon carcharias), to the list of potential victims. A subadult male white shark off Guadelupe Island, Mexico, was observed with a fresh cookiecutter shark bite next to its mouth, as well as a second crescent-shaped scar. A subadult male white shark was tracked in the same location and showed diel changes in depth, with the shark occupying shallow water (
Les Christidis - One of the best experts on this subject based on the ideXlab platform.
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Metal and metalloid concentrations in the tissues of dusky Carcharhinus obscurus, sandbar C. plumbeus and white Carcharodon carcharias sharks from south-eastern Australian waters, and the implications for human consumption.
Marine pollution bulletin, 2015Co-Authors: Jann M Gilbert, Paul A. Butcher, Victor M. Peddemors, Amanda J Reichelt-brushett, Shane P Mcgrath, Alison C Bowling, Les ChristidisAbstract:Shark fisheries have expanded due to increased demand for shark products. As long-lived apex predators, sharks are susceptible to bioaccumulation of metals and metalloids, and biomagnification of some such as Hg, primarily through diet. This may have negative health implications for human consumers. Concentrations of Hg, As, Cd, Cu, Fe, Se and Zn were analysed in muscle, liver and fin fibres (ceratotrichia) from dusky Carcharhinus obscurus, sandbar Carcharhinus plumbeus, and white Carcharodon carcharias sharks from south-eastern Australian waters. Concentrations of analytes were generally higher in liver than in muscle and lowest in fin fibres. Muscle tissue concentrations of Hg were significantly correlated with total length, and >50% of sampled individuals had concentrations above Food Standards Australia New Zealand's maximum limit (1 mg kg(-1) ww). Arsenic concentrations were also of concern, particularly in fins. Results warrant further investigation to accurately assess health risks for regular consumption of shark products.
Bruce J. Macfadden - One of the best experts on this subject based on the ideXlab platform.
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origin of the white shark Carcharodon lamniformes lamnidae based on recalibration of the upper neogene pisco formation of peru
Palaeontology, 2012Co-Authors: Dana J Ehret, Bruce J. Macfadden, Douglas S Jones, Thomas J Devries, David A Foster, Rodolfo SalasgismondiAbstract:Abstract: The taxonomic origin of the white shark, Carcharodon, is a highly debated subject. New fossil evidence presented in this study suggests that the genus is derived from the broad-toothed ‘mako’, Carcharodon (Cosmopolitodus) hastalis, and includes the new species C. hubbelli sp. nov. – a taxon that demonstrates a transition between C. hastalis and Carcharodon carcharias. Specimens from the Pisco Formation clearly demonstrate an evolutionary mosaic of characters of both recent C. carcharias and fossil C. hastalis. Characters diagnostic to C. carcharias include the presence tooth serrations and a symmetrical first upper anterior tooth that is the largest in the tooth row, while those indicative of C. hastalis include a mesially slanted third anterior (intermediate) tooth. We also provide a recalibration of critical fossil horizons within the Pisco Formation, Peru using zircon U-Pb dating and strontium-ratio isotopic analysis. The recalibration of the absolute dates suggests that Carcharodon hubbelli sp. nov. is Late Miocene (6–8 Ma) in age. This research revises and elucidates lamnid shark evolution based on the calibration of the Neogene Pisco Formation.
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exceptional preservation of the white shark Carcharodon lamniformes lamnidae from the early pliocene of peru
Journal of Vertebrate Paleontology, 2009Co-Authors: Dana J Ehret, Gordon Hubbell, Bruce J. MacfaddenAbstract:ABSTRACT An exceptionally well-preserved white shark fossil (Carcharodon sp.) is described here from the early Pliocene (ca. 4 Ma) Pisco Formation of southwestern Peru. This specimen preserves 222 teeth and 45 vertebrae as well as fragmentary jaws. The teeth show characters of Carcharodon, including weak serrations and a symmetrical first anterior tooth that is the largest in the tooth row. This dentition also shows a character of Isurus with a distally inclined but mesially slanted intermediate tooth. Although the Pisco specimen demonstrates characters of both Isurus, also known form the Pisco Formation, and modern Carcharodon carcharias, it is assigned to the genus Carcharodon and referred to herein as Carcharodon sp. While Carcharodon sp. From the Pisco Formation shows numerous diagnostic characteristics shared with C. carcharias, it differs from the extant species in having a distal inclination of the intermediate tooth. The precaudal vertebral centra of the Pisco Carcharodon preserve distinctive dark...
Dana J Ehret - One of the best experts on this subject based on the ideXlab platform.
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origin of the white shark Carcharodon lamniformes lamnidae based on recalibration of the upper neogene pisco formation of peru
Palaeontology, 2012Co-Authors: Dana J Ehret, Bruce J. Macfadden, Douglas S Jones, Thomas J Devries, David A Foster, Rodolfo SalasgismondiAbstract:Abstract: The taxonomic origin of the white shark, Carcharodon, is a highly debated subject. New fossil evidence presented in this study suggests that the genus is derived from the broad-toothed ‘mako’, Carcharodon (Cosmopolitodus) hastalis, and includes the new species C. hubbelli sp. nov. – a taxon that demonstrates a transition between C. hastalis and Carcharodon carcharias. Specimens from the Pisco Formation clearly demonstrate an evolutionary mosaic of characters of both recent C. carcharias and fossil C. hastalis. Characters diagnostic to C. carcharias include the presence tooth serrations and a symmetrical first upper anterior tooth that is the largest in the tooth row, while those indicative of C. hastalis include a mesially slanted third anterior (intermediate) tooth. We also provide a recalibration of critical fossil horizons within the Pisco Formation, Peru using zircon U-Pb dating and strontium-ratio isotopic analysis. The recalibration of the absolute dates suggests that Carcharodon hubbelli sp. nov. is Late Miocene (6–8 Ma) in age. This research revises and elucidates lamnid shark evolution based on the calibration of the Neogene Pisco Formation.
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exceptional preservation of the white shark Carcharodon lamniformes lamnidae from the early pliocene of peru
Journal of Vertebrate Paleontology, 2009Co-Authors: Dana J Ehret, Gordon Hubbell, Bruce J. MacfaddenAbstract:ABSTRACT An exceptionally well-preserved white shark fossil (Carcharodon sp.) is described here from the early Pliocene (ca. 4 Ma) Pisco Formation of southwestern Peru. This specimen preserves 222 teeth and 45 vertebrae as well as fragmentary jaws. The teeth show characters of Carcharodon, including weak serrations and a symmetrical first anterior tooth that is the largest in the tooth row. This dentition also shows a character of Isurus with a distally inclined but mesially slanted intermediate tooth. Although the Pisco specimen demonstrates characters of both Isurus, also known form the Pisco Formation, and modern Carcharodon carcharias, it is assigned to the genus Carcharodon and referred to herein as Carcharodon sp. While Carcharodon sp. From the Pisco Formation shows numerous diagnostic characteristics shared with C. carcharias, it differs from the extant species in having a distal inclination of the intermediate tooth. The precaudal vertebral centra of the Pisco Carcharodon preserve distinctive dark...
Jann M Gilbert - One of the best experts on this subject based on the ideXlab platform.
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Metal and metalloid concentrations in the tissues of dusky Carcharhinus obscurus, sandbar C. plumbeus and white Carcharodon carcharias sharks from south-eastern Australian waters, and the implications for human consumption.
Marine pollution bulletin, 2015Co-Authors: Jann M Gilbert, Paul A. Butcher, Victor M. Peddemors, Amanda J Reichelt-brushett, Shane P Mcgrath, Alison C Bowling, Les ChristidisAbstract:Shark fisheries have expanded due to increased demand for shark products. As long-lived apex predators, sharks are susceptible to bioaccumulation of metals and metalloids, and biomagnification of some such as Hg, primarily through diet. This may have negative health implications for human consumers. Concentrations of Hg, As, Cd, Cu, Fe, Se and Zn were analysed in muscle, liver and fin fibres (ceratotrichia) from dusky Carcharhinus obscurus, sandbar Carcharhinus plumbeus, and white Carcharodon carcharias sharks from south-eastern Australian waters. Concentrations of analytes were generally higher in liver than in muscle and lowest in fin fibres. Muscle tissue concentrations of Hg were significantly correlated with total length, and >50% of sampled individuals had concentrations above Food Standards Australia New Zealand's maximum limit (1 mg kg(-1) ww). Arsenic concentrations were also of concern, particularly in fins. Results warrant further investigation to accurately assess health risks for regular consumption of shark products.