The Experts below are selected from a list of 1821 Experts worldwide ranked by ideXlab platform
Charlie Huveneers - One of the best experts on this subject based on the ideXlab platform.
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effectiveness of novel fabrics to resist punctures and lacerations from white shark carcharodon Carcharias implications to reduce injuries from shark bites
PLOS ONE, 2019Co-Authors: Sasha K Whitmarsh, Dhara B Amin, John J Costi, Joshua D Dennis, Charlie HuveneersAbstract:Increases in the number of shark bites, along with increased media attention on shark-human interactions has led to growing interest in preventing injuries from shark bites through the use of personal mitigation measures. The leading cause of fatality from shark bite victims is blood loss; thus reducing haemorrhaging may provide additional time for a shark bite victim to be attended to by emergency services. Despite previous shark-proof suits being bulky and cumbersome, new technological advances in fabric has allowed the development of lightweight alternatives that can be incorporated onto traditional wetsuits. The ability for these fabrics to withstand shark bites has not been scientifically tested. In this report, we compared two types of recently developed protective fabrics that incorporated ultra-high molecular weight polyethylene (UHMWPE) fibre onto neoprene (SharkStop and ActionTX) and compared them to standard neoprene alternatives. We tested nine different fabric variants using three different tests, laboratory-based puncture and laceration tests, along with field-based trials involving white sharks Carcharodon Carcharias. Field-based trials consisted of measuring C. Carcharias bite force and quantifying damages to the new fabrics following a bite from 3-4 m total length C. Carcharias. We found that SharkStop and ActionTX fabric variants were more resistant to puncture, laceration, and bites from C. Carcharias. More force was required to puncture the new fabrics compared to control fabrics (laboratory-based tests), and cuts made to the new fabrics were smaller and shallower than those on standard neoprene for both types of test, i.e. laboratory and field tests. Our results showed that UHMWPE fibre increased the resistance of neoprene to shark bites. Although the use of UHMWPE fibre (e.g. SharkStop and ActionTX) may therefore reduce blood loss resulting from a shark bite, research is needed to assess if the reduction in damages to the fabrics extends to human tissues and decreased injuries.
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Stereo-video, length estimate, and camera calibration data from Eyes on the size: accuracy of visual length estimates of white sharks, Carcharodon Carcharias
2019Co-Authors: Cameron May, Lauren Meyer, Sasha Whitmarsh, Charlie HuveneersAbstract:Visual estimates have been used extensively to determine the length of large organisms that are logistically challenging to measure. However, there has been little effort to quantify the accuracy or validity of this technique despite inaccurate size estimates leading to incorrect population assessments and misinformed management strategies. Here, we compared visually estimated total length measurements of white sharks, Carcharodon Carcharias, during cage-diving operations with measurements obtained from stereo-video cameras and assessed the accuracy of those estimates in relation to suspected biases (shark size, and observer experience and gender) using generalized linear mixed models and linear regressions. Observer experience on board cage-diving vessels had the greatest effect on the accuracy of visual length estimates, with scientists being more accurate (mean accuracy ± standard error: 23.0 ± 16.5 cm) than crew (39.9 ± 33.8 cm) and passengers (49.4 ± 38.5 cm). Observer gender and shark size had no impact on the overall accuracy of visual length estimates, but passengers overestimated sharks less than 3 m and underestimated sharks greater than 3 m. Our findings show that experience measuring animals is the most substantial driver of accurate visual length estimates regardless of the amount of exposure to the species being measured. Scientists were most accurate, even though crew observes white sharks more frequently. Our results show that visual length estimates are not impacted by shark size and are a valid measurement tool for many aspects of C. Carcharias research, provided they come from people who have previously been involved in measuring animals, i.e. scientists
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Effects of auditory and visual stimuli on shark feeding behaviour: the disco effect
Marine Biology, 2017Co-Authors: Laura A. Ryan, R.d. Mccauley, S. P. Collin, Jan M. Hemmi, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Charlie Huveneers, Kara E. Yopak, Caroline C. KerrAbstract:Sensory systems play a central role in guiding animal behaviour. They can be manipulated to alter behavioural outcomes to limit negative interactions between humans and animals. Sharks are often seen as a threat to humans and there has been increasing interest in developing shark mitigation devices. Previous research has concentrated on stimulating the electrosensory and olfactory systems of sharks, whereas the influence of light and sound on their behaviour has received little attention. In this study, the effects of an intense strobe light and a loud, artificial sound composed of mixed frequencies and intensities on shark behaviour were assessed. We tested these stimuli individually and in combination on wild-caught captive Port Jackson (Heterodontus portusjacksoni) and epaulette (Hemiscyllium ocellatum) sharks in aquaria and on wild great white sharks (Carcharodon Carcharias) in the field. When presented alone and in combination with sound, the lights reduced the number of times that the bait was taken by both H. portusjacksoni and H. ocellatum in captivity. The strobe light alone, however, did not affect the behaviour of white sharks, but when presented in combination with sound, white sharks spent significantly less time in proximity to the bait. As the lights and sound presented in this study did not show a pronounced deterrent effect on C. Carcharias, we do not advise their use as a strategy for mitigating shark–human interactions. However, due to the potential effectiveness of strobe lights in deterring other species of sharks, there may be applications for this approach in the reduction of fisheries bycatch.
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The economic value of shark-diving tourism in Australia
Reviews in Fish Biology and Fisheries, 2017Co-Authors: Charlie Huveneers, Mark G. Meekan, Kirin Apps, Luciana C. Ferreira, David Pannell, Gabriel M. S. ViannaAbstract:Shark-diving is part of a rapidly growing industry focused on marine wildlife tourism. Our study aimed to provide an estimate of the economic value of shark-diving tourism across Australia by comprehensively surveying the whale shark ( Rhincodon typus ), white shark ( Carcharodon Carcharias ), grey nurse shark ( Carcharias taurus ), and reef shark (mostly Carcharhinus amblyrhynchos and Triaenodon obesus ) diving industries using a standardised approach. A socio-economic survey targeted tourist divers between March 2013 and June 2014 and collected information on expenditures related to diving, accommodation, transport, living costs, and other related activities during divers’ trips. A total of 711 tourist surveys were completed across the four industries, with the total annual direct expenditure by shark divers in Australia estimated conservatively at $25.5 M. Additional expenditure provided by the white-shark and whale-shark-diving industries totalled $8.1 and $12.5 M for the Port Lincoln and Ningaloo Reef regions respectively. International tourists diving with white sharks also expended another $0.9 M in airfares and other activities while in Australia. These additional revenues show that the economic value of this type of tourism do not flow solely to the industry, but are also spread across the region where it is hosted. This highlights the need to ensure a sustainable dive-tourism industry through adequate management of both shark-diver interactions and biological management of the species on which it is based. Our study also provides standardised estimates which allow for future comparison of the scale of other wildlife tourism industries (not limited to sharks) within or among countries.
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how close is too close the effect of a non lethal electric shark deterrent on white shark behaviour
PLOS ONE, 2016Co-Authors: Ryan M Kempster, Laura A. Ryan, Caroline C. Kerr, Lucille Chapuis, Charlie Huveneers, Channing A. Egeberg, Nathan S. Hart, Carl J Schmidt, Enrico GennariAbstract:Sharks play a vital role in the health of marine ecosystems, but the potential threat that sharks pose to humans is a reminder of our vulnerability when entering the ocean. Personal shark deterrents are being marketed as the solution to mitigate the threat that sharks pose. However, the effectiveness claims of many personal deterrents are based on our knowledge of shark sensory biology rather than robust testing of the devices themselves, as most have not been subjected to independent scientific studies. Therefore, there is a clear need for thorough testing of commercially available shark deterrents to provide the public with recommendations of their effectiveness. Using a modified stereo-camera system, we quantified behavioural interactions between white sharks (Carcharodon Carcharias) and a baited target in the presence of a commercially available, personal electric shark deterrent (Shark Shield Freedom7™). The stereo-camera system enabled an accurate assessment of the behavioural responses of C. Carcharias when encountering a non-lethal electric field many times stronger than what they would naturally experience. Upon their first observed encounter, all C. Carcharias were repelled at a mean (± std. error) proximity of 131 (± 10.3) cm, which corresponded to a mean voltage gradient of 9.7 (± 0.9) V/m. With each subsequent encounter, their proximity decreased by an average of 11.6 cm, which corresponded to an increase in tolerance to the electric field by an average of 2.6 (± 0.5) V/m per encounter. Despite the increase in tolerance, sharks continued to be deterred from interacting for the duration of each trial when in the presence of an active Shark Shield™. Furthermore, the findings provide no support to the theory that electric deterrents attract sharks. The results of this study provide quantitative evidence of the effectiveness of a non-lethal electric shark deterrent, its influence on the behaviour of C. Carcharias, and an accurate method for testing other shark deterrent technologies.
Enrico Gennari - One of the best experts on this subject based on the ideXlab platform.
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Not all electric shark deterrents are made equal: Effects of a commercial electric anklet deterrent on white shark behaviour - Fig 3
2019Co-Authors: Channing A. Egeberg, Caroline C. Kerr, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Kara E. Yopak, Nathan S. Hart, Laura Ryan, Carl Schmidt, Shaun P. CollinAbstract:Screenshots of C. Carcharias encountering an active ESDS: (A) C. Carcharias interacting with the bait (Type 1 interaction); (B) C. Carcharias biting the bait (Type 2 interaction).
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Plot to show the voltage gradient decline of the ESDS with increasing distance.
2019Co-Authors: Channing A. Egeberg, Caroline C. Kerr, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Kara E. Yopak, Nathan S. Hart, Laura Ryan, Carl Schmidt, Shaun P. CollinAbstract:The short-dashed arrows indicate the average deterrent threshold of C. Carcharias (15.7 V/m [22]) and the corresponding estimated effective deterrent range of the ESDS (11.6 cm). The long-dashed arrows indicate the average deterrent threshold of C. Carcharias during their first encounter with an electric field (9.7 V/m [22]) and the corresponding estimated effective deterrent range of the ESDS (16.9 cm). Red dots depict actual voltage gradient measurements recorded for the ESDS. Voltage gradient curve plotted using Harris model: y = 1/(-0.06s82+0.0239x^0.6961).
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Not all electric shark deterrents are made equal: Effects of a commercial electric anklet deterrent on white shark behaviour
2019Co-Authors: Channing A. Egeberg, Caroline C. Kerr, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Kara E. Yopak, Nathan S. Hart, Laura Ryan, Carl Schmidt, Shaun P. CollinAbstract:Personal shark deterrents offer the potential of a non-lethal solution to protect individuals from negative interactions with sharks, but the claims of effectiveness of most deterrents are based on theory rather than robust testing of the devices themselves. Therefore, there is a clear need for thorough testing of commercially available shark deterrents to provide the public with information on their effectiveness. Using a modified stereo-camera system, we quantified behavioural interactions between Carcharodon Carcharias (white sharks) and a baited target in the presence of a commercially available electric anklet shark deterrent, the Electronic Shark Defense System (ESDS). The stereo-camera system enabled accurate assessment of the behavioural responses of C. Carcharias when approaching an ESDS. We found that the ESDS had limited meaningful effect on the behaviour of C. Carcharias, with no significant reduction in the proportion of sharks interacting with the bait in the presence of the active device. At close proximity (< 15.5 cm), the active ESDS did show a significant reduction in the number of sharks biting the bait, but this was countered by an increase in other, less aggressive, interactions. The ESDS discharged at a frequency of 7.8 Hz every 5.1 s for 2.5 s, followed by an inactive interval of 2.6 s. As a result, many sharks may have encountered the device in its inactive state, resulting in a reduced behavioural response. Consequently, decreasing the inactive interval between pulses may improve the overall effectiveness of the device, but this would not improve the effective deterrent range of the device, which is primarily a factor of the voltage gradient rather than the stimulus frequency. In conclusion, given the very short effective range of the ESDS and its unreliable deterrent effect, combined with the fact that shark-bite incidents are very rare, it is unlikely that the current device would significantly reduce the risk of a negative interaction with C. Carcharias.
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Diagram of a Remote Monitoring Research Apparatus (ReMoRA).
2019Co-Authors: Channing A. Egeberg, Caroline C. Kerr, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Kara E. Yopak, Nathan S. Hart, Laura Ryan, Carl Schmidt, Shaun P. CollinAbstract:(A) shows the ReMoRA in its deployed configuration with downward-facing cameras. (B) shows the measurements recorded to calculate proximity of C. Carcharias to the ESDS electrode closest to the bait canister. Using Event Measure software, the closest part of a shark’s head to the electrode is marked via the left and right cameras (a), and then the centre of the ESDS electrode is also marked (b), which accurately calculates the closest observable proximity of the shark in three-dimensional space (c), taking into account both the vertical and horizontal axis. For clarity, the electrodes of the ESDS are displayed in white to highlight their position.
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Effects of auditory and visual stimuli on shark feeding behaviour: the disco effect
Marine Biology, 2017Co-Authors: Laura A. Ryan, R.d. Mccauley, S. P. Collin, Jan M. Hemmi, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Charlie Huveneers, Kara E. Yopak, Caroline C. KerrAbstract:Sensory systems play a central role in guiding animal behaviour. They can be manipulated to alter behavioural outcomes to limit negative interactions between humans and animals. Sharks are often seen as a threat to humans and there has been increasing interest in developing shark mitigation devices. Previous research has concentrated on stimulating the electrosensory and olfactory systems of sharks, whereas the influence of light and sound on their behaviour has received little attention. In this study, the effects of an intense strobe light and a loud, artificial sound composed of mixed frequencies and intensities on shark behaviour were assessed. We tested these stimuli individually and in combination on wild-caught captive Port Jackson (Heterodontus portusjacksoni) and epaulette (Hemiscyllium ocellatum) sharks in aquaria and on wild great white sharks (Carcharodon Carcharias) in the field. When presented alone and in combination with sound, the lights reduced the number of times that the bait was taken by both H. portusjacksoni and H. ocellatum in captivity. The strobe light alone, however, did not affect the behaviour of white sharks, but when presented in combination with sound, white sharks spent significantly less time in proximity to the bait. As the lights and sound presented in this study did not show a pronounced deterrent effect on C. Carcharias, we do not advise their use as a strategy for mitigating shark–human interactions. However, due to the potential effectiveness of strobe lights in deterring other species of sharks, there may be applications for this approach in the reduction of fisheries bycatch.
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...
Caroline C. Kerr - One of the best experts on this subject based on the ideXlab platform.
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Not all electric shark deterrents are made equal: Effects of a commercial electric anklet deterrent on white shark behaviour - Fig 3
2019Co-Authors: Channing A. Egeberg, Caroline C. Kerr, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Kara E. Yopak, Nathan S. Hart, Laura Ryan, Carl Schmidt, Shaun P. CollinAbstract:Screenshots of C. Carcharias encountering an active ESDS: (A) C. Carcharias interacting with the bait (Type 1 interaction); (B) C. Carcharias biting the bait (Type 2 interaction).
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Plot to show the voltage gradient decline of the ESDS with increasing distance.
2019Co-Authors: Channing A. Egeberg, Caroline C. Kerr, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Kara E. Yopak, Nathan S. Hart, Laura Ryan, Carl Schmidt, Shaun P. CollinAbstract:The short-dashed arrows indicate the average deterrent threshold of C. Carcharias (15.7 V/m [22]) and the corresponding estimated effective deterrent range of the ESDS (11.6 cm). The long-dashed arrows indicate the average deterrent threshold of C. Carcharias during their first encounter with an electric field (9.7 V/m [22]) and the corresponding estimated effective deterrent range of the ESDS (16.9 cm). Red dots depict actual voltage gradient measurements recorded for the ESDS. Voltage gradient curve plotted using Harris model: y = 1/(-0.06s82+0.0239x^0.6961).
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Not all electric shark deterrents are made equal: Effects of a commercial electric anklet deterrent on white shark behaviour
2019Co-Authors: Channing A. Egeberg, Caroline C. Kerr, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Kara E. Yopak, Nathan S. Hart, Laura Ryan, Carl Schmidt, Shaun P. CollinAbstract:Personal shark deterrents offer the potential of a non-lethal solution to protect individuals from negative interactions with sharks, but the claims of effectiveness of most deterrents are based on theory rather than robust testing of the devices themselves. Therefore, there is a clear need for thorough testing of commercially available shark deterrents to provide the public with information on their effectiveness. Using a modified stereo-camera system, we quantified behavioural interactions between Carcharodon Carcharias (white sharks) and a baited target in the presence of a commercially available electric anklet shark deterrent, the Electronic Shark Defense System (ESDS). The stereo-camera system enabled accurate assessment of the behavioural responses of C. Carcharias when approaching an ESDS. We found that the ESDS had limited meaningful effect on the behaviour of C. Carcharias, with no significant reduction in the proportion of sharks interacting with the bait in the presence of the active device. At close proximity (< 15.5 cm), the active ESDS did show a significant reduction in the number of sharks biting the bait, but this was countered by an increase in other, less aggressive, interactions. The ESDS discharged at a frequency of 7.8 Hz every 5.1 s for 2.5 s, followed by an inactive interval of 2.6 s. As a result, many sharks may have encountered the device in its inactive state, resulting in a reduced behavioural response. Consequently, decreasing the inactive interval between pulses may improve the overall effectiveness of the device, but this would not improve the effective deterrent range of the device, which is primarily a factor of the voltage gradient rather than the stimulus frequency. In conclusion, given the very short effective range of the ESDS and its unreliable deterrent effect, combined with the fact that shark-bite incidents are very rare, it is unlikely that the current device would significantly reduce the risk of a negative interaction with C. Carcharias.
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Diagram of a Remote Monitoring Research Apparatus (ReMoRA).
2019Co-Authors: Channing A. Egeberg, Caroline C. Kerr, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Kara E. Yopak, Nathan S. Hart, Laura Ryan, Carl Schmidt, Shaun P. CollinAbstract:(A) shows the ReMoRA in its deployed configuration with downward-facing cameras. (B) shows the measurements recorded to calculate proximity of C. Carcharias to the ESDS electrode closest to the bait canister. Using Event Measure software, the closest part of a shark’s head to the electrode is marked via the left and right cameras (a), and then the centre of the ESDS electrode is also marked (b), which accurately calculates the closest observable proximity of the shark in three-dimensional space (c), taking into account both the vertical and horizontal axis. For clarity, the electrodes of the ESDS are displayed in white to highlight their position.
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Effects of auditory and visual stimuli on shark feeding behaviour: the disco effect
Marine Biology, 2017Co-Authors: Laura A. Ryan, R.d. Mccauley, S. P. Collin, Jan M. Hemmi, Enrico Gennari, Ryan M Kempster, Lucille Chapuis, Charlie Huveneers, Kara E. Yopak, Caroline C. KerrAbstract:Sensory systems play a central role in guiding animal behaviour. They can be manipulated to alter behavioural outcomes to limit negative interactions between humans and animals. Sharks are often seen as a threat to humans and there has been increasing interest in developing shark mitigation devices. Previous research has concentrated on stimulating the electrosensory and olfactory systems of sharks, whereas the influence of light and sound on their behaviour has received little attention. In this study, the effects of an intense strobe light and a loud, artificial sound composed of mixed frequencies and intensities on shark behaviour were assessed. We tested these stimuli individually and in combination on wild-caught captive Port Jackson (Heterodontus portusjacksoni) and epaulette (Hemiscyllium ocellatum) sharks in aquaria and on wild great white sharks (Carcharodon Carcharias) in the field. When presented alone and in combination with sound, the lights reduced the number of times that the bait was taken by both H. portusjacksoni and H. ocellatum in captivity. The strobe light alone, however, did not affect the behaviour of white sharks, but when presented in combination with sound, white sharks spent significantly less time in proximity to the bait. As the lights and sound presented in this study did not show a pronounced deterrent effect on C. Carcharias, we do not advise their use as a strategy for mitigating shark–human interactions. However, due to the potential effectiveness of strobe lights in deterring other species of sharks, there may be applications for this approach in the reduction of fisheries bycatch.
Alicia H Escalante - One of the best experts on this subject based on the ideXlab platform.
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Tooth row counts, vicariance, and the distribution of the sand tiger shark Carcharias taurus
Ecography, 2003Co-Authors: Luis O Lucifora, Roberto Carlos Menni, Alberto Luis Cione, Alicia H EscalanteAbstract:Geographic variation in tooth row counts among sand tiger sharks Carcharias taurus (Chondrichthyes), from the SW Atlantic, NW Atlantic and the East China Sea is analyzed in this paper. We found significant differences between sand tigers from the SW Atlantic (Southern Hemisphere population) and each of the other two (Northern Hemisphere) regions in the number of upper lateral tooth rows, and between individuals from the SW Atlantic and the East China Sea in the total number of upper tooth rows. Sand tiger sharks from the two Northern Hemisphere populations did not differ in any of the studied variables. Our results agree with comparisons of vertebral counts between sand tiger sharks from Southern and Northern Hemispheres. Both lines of evidence suggest that Southern and Northern Hemisphere populations of C. taurus were isolated to a larger extent than populations of the Northern Hemisphere. The fossil record of the genus Carcharias begins in the Early Cretaceous and C. taurus is certainly known since the Late Miocene. During the Miocene, the Tethys Sea separating northern and southern land masses was still present and it provided a continuous temperate shallow sea that could allow dispersal of sand tiger sharks along Northern Hemisphere seas. Independent observations on the distribution and evolutionary history of the genera Myripristis, Neoniphon, Sargocentron and Aphanius, and genetic studies on the temperate shark genus Mustelus that indicate a close relationship between the Indo-Pacific M. manazo and the Mediterranean M. asterias suggest that this hypothesis is plausible and deserves to be tested.