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Julia L. Y. Spaet - One of the best experts on this subject based on the ideXlab platform.
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Weak population structure of the Spot-tail shark Carcharhinus sorrah and the Blacktip shark C. limbatus along the coasts of the Arabian Peninsula, Pakistan, and South Africa.
Ecology and Evolution, 2018Co-Authors: Dareen Almojil, Geremy Cliff, Julia L. Y. SpaetAbstract:The increase in demand for shark meat and fins has placed shark populations worldwide under high fishing pressure. In the Arabian region, the spot-tail shark Carcharhinus sorrah and the Blacktip shark Carcharhinus limbatus are among the most exploited species. In this study, we investigated the population genetic structure of C. sorrah (n = 327) along the coasts of the Arabian Peninsula and of C. limbatus (n = 525) along the Arabian coasts, Pakistan, and KwaZulu-Natal, South Africa, using microsatellite markers (15 and 11 loci, respectively). Our findings support weak population structure in both species. Carcharhinus sorrah exhibited a fine structure, subdividing the area into three groups. The first group comprises all samples from Bahrain, the second from the UAE and Yemen, and the third from Oman. Similarly, C. limbatus exhibited population subdivision into three groups. The first group, comprising samples from Bahrain and Kuwait, was highly differentiated from the second and third groups, comprising samples from Oman, Pakistan, the UAE, and Yemen; and South Africa and the Saudi Arabian Red Sea, respectively. Population divisions were supported by pairwise FST values and discriminant analysis of principal components (DAPC), but not by STRUCTURE. We suggest that the mostly low but significant pairwise FST values in our study are suggestive of fine population structure, which is possibly attributable to behavioral traits such as residency in C. sorrah and site fidelity and philopatry in C. limbatus. However, for all samples obtained from the northern parts of the Gulf (Bahrain and/or Kuwait) in both species, the higher but significant pairwise FST values could possibly be a result of founder effects during the Tethys Sea closure. Based on DAPC and FST results, we suggest each population to be treated as independent management unit, as conservation concerns emerge.
Gregoire Metais - One of the best experts on this subject based on the ideXlab platform.
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new tropical carcharhinids chondrichthyes carcharhiniformes from the late eocene early oligocene of balochistan pakistan paleoenvironmental and paleogeographic implications
Journal of Southeast Asian Earth Sciences, 2007Co-Authors: Sylvain Adnet, Pierreolivier Antoine, S Hassan R Baqri, Jeanyves Crochet, Laurent Marivaux, Jeanloup Welcomme, Gregoire MetaisAbstract:New selachians (sharks and rays) have been collected from several late Eocene and early Oligocene marine localities in the Bugti Hills (Balochistan, Pakistan). Two new species of Requiem sharks (close to the Recent ?Bull shark?) are described : Carcharhinus balochensis and Carcharhinus perseus. The rest of the fauna is notable for the strong representation of Carcharhiniformes. These selachian faunas represent a unique tropical association for the Oligocene period and one of the first modern tropical selachian faunas, with modern taxa such as the two new species of ?Bull sharks?, Negaprion sp. and one of the first occurrences of Sphyrna sp. Moreover, these faunas permit paleoenvironmental interpretation of adjacent land masses. The relatively modern aspect of these faunas, compared with other contemporaneous and younger selachian associations from Atlantic and Mediterranean seas, suggests biogeographic isolation of selachian communities living in eastern and western parts of the Tethys before its final closure during the early-middle Miocene.
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New tropical carcharhinids (chondrichthyes, carcharhiniformes) from the late Eocene early Oligocene of Balochistan, Pakistan: Paleoenvironmental and paleogeographic implications
Journal of Southeast Asian earth sciences, 2007Co-Authors: Sylvain Adnet, Jeanyves Crochet, Laurent Marivaux, Jeanloup Welcomme, P.-o. Antoine, S. R. Hassan Baqri, Gregoire MetaisAbstract:New selachians (sharks and rays) have been collected from several late Eocene and early Oligocene marine localities in the Bugti Hills (Balochistan, Pakistan). Two new species of Requiem sharks (close to the Recent ?Bull shark?) are described : Carcharhinus balochensis and Carcharhinus perseus. The rest of the fauna is notable for the strong representation of Carcharhiniformes. These selachian faunas represent a unique tropical association for the Oligocene period and one of the first modern tropical selachian faunas, with modern taxa such as the two new species of ?Bull sharks?, Negaprion sp. and one of the first occurrences of Sphyrna sp. Moreover, these faunas permit paleoenvironmental interpretation of adjacent land masses. The relatively modern aspect of these faunas, compared with other contemporaneous and younger selachian associations from Atlantic and Mediterranean seas, suggests biogeographic isolation of selachian communities living in eastern and western parts of the Tethys before its final closure during the early-middle Miocene.
William T. White - One of the best experts on this subject based on the ideXlab platform.
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Lost before found: A new species of whaler shark Carcharhinus obsolerus from the Western Central Pacific known only from historic records.
PloS one, 2019Co-Authors: William T. White, Peter Kyne, Mark HarrisAbstract:Carcharhinus obsolerus is described based on three specimens from Borneo, Thailand and Vietnam in the Western Central Pacific. It belongs to the porosus subgroup which is characterised by having the second dorsal-fin insertion opposite the anal-fin midbase. It most closely resembles C. borneensis but differs in tooth morphology and counts and a number of morphological characters, including lack of enlarged hyomandibular pores which are diagnostic of C. borneensis. The historic range of C. obsolerus sp. nov. is under intense fishing pressure and this species has not been recorded anywhere in over 80 years. There is an urgent need to assess its extinction risk status for the IUCN Red List of Threatened Species. With so few known records, there is a possibility that Carcharhinus obsolerus sp. nov. has been lost from the marine environment before any understanding could be gained of its full historic distribution, biology, ecosystem role, and importance in local fisheries.
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Lower jaw dentition in the three most similar Carcharhinus species.
2019Co-Authors: William T. White, Peter M. Kyne, Mark HarrisAbstract:A. Carcharhinus borneensis (PMH244-1, mature female 661 mm TL); B. Carcharhinus cerdale (PMH329-01, juvenile male 887 mm TL; left side of jaw with image reversed); C. Carcharhinus macloti (PMH057-15, mature female 1090 mm TL).
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A redescription of Carcharhinus dussumieri and C. sealei , with resurrection of C. coatesi and C. tjutjot as valid species (Chondrichthyes: Carcharhinidae)
Zootaxa, 2012Co-Authors: William T. WhiteAbstract:A taxonomic re-evaluation of the Carcharhinus sealei-dussumieri group using meristic and morphological data revealedthat this group consists of 5 species. Two species, Carcharhinus coatesi (Whitley, 1939) from northern Australia and prob-ably New Guinea and C. tjutjot (Bleeker, 1852) from Indonesian to Taiwan, are resurrected as valid species and togetherwith C. dussumieri and C. sealei are redescribed. Garrick’s lectotype designation of C. dussumieri and C. tjutjot areretained. A neotype for C. sealei, collected from the same locality as the holotype which was destroyed during World WarII, is designated. A fifth, possibly undescribed species (Carcharhinus sp.) is also noted from the Western Indian Oceanand its affinities briefly discussed. The four redescribed species are very similarly morphologically but can be distin-guished by a combination of meristic, morphological, dental and colour characters. The most important characters for dis-tinguishing these species are: vertebral counts, tooth counts, tooth morphology, shape of first dorsal and pectoral fins,second dorsal fin colouration, and mouth width. Two independent molecular studies have produced results which closely correlate with and support the findings of this study.
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A redescription of Carcharhinus dussumieri and C. sealei, with resurrection of C. coatesi and C. tjutjot as valid species (Chondrichthyes: Carcharhinidae)
Zootaxa, 2012Co-Authors: William T. WhiteAbstract:A taxonomic re-evaluation of the Carcharhinus sealei-dussumieri group using meristic and morphological data revealedthat this group consists of 5 species. Two species, Carcharhinus coatesi (Whitley, 1939) from northern Australia and prob-ably New Guinea and C. tjutjot (Bleeker, 1852) from Indonesian to Taiwan, are resurrected as valid species and togetherwith C. dussumieri and C. sealei are redescribed. Garrick’s lectotype designation of C. dussumieri and C. tjutjot areretained. A neotype for C. sealei, collected from the same locality as the holotype which was destroyed during World WarII, is designated. A fifth, possibly undescribed species (Carcharhinus sp.) is also noted from the Western Indian Oceanand its affinities briefly discussed. The four redescribed species are very similarly morphologically but can be distin-guished by a combination of meristic, morphological, dental and colour characters. The most important characters for dis-tinguishing these species are: vertebral counts, tooth counts, tooth morphology, shape of first dorsal and pectoral fins,second dorsal fin colouration, and mouth width. Two independent molecular studies have produced results which closely correlate with and support the findings of this study.
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Rediscovery and redescription of the smoothtooth blacktip shark, Carcharhinus leiodon (Carcharhinidae), from Kuwait, with notes on its possible conservation status
Marine and Freshwater Research, 2011Co-Authors: Alec B. M. Moore, William T. White, Robert D. Ward, Gavin J. P. Naylor, Richard PeirceAbstract:The smoothtooth blacktip shark, Carcharhinus leiodon, is one of the rarest whaler shark species of the genus Carcharhinus, previously known only from the holotype collected over 100 years ago from the Arabian Sea coast of Yemen. Recent market surveys in the Persian (Arabian) Gulf rediscovered 25 specimens (~2% of individual sharks recorded) in Kuwait, ~3000 km away from the type location. This study combined morphometric and molecular approaches to provide a detailed redescription of this species based on new material, as well as the first information on fresh colouration, size range and maturity. Sequences from two separate regions of the mitochondrial genome (COI and ND2) support the identity of C. leiodon as a distinct species, closely related to C. limbatus, C. amblyrhynchoides and C. tilstoni. Carcharhinus leiodon is superficially similar to, but clearly distinct from, C. melanopterus and C. amblyrhynchoides. The previously uncertain type locality of C. leiodon is considered to be correct, and the narrow range and unusual disjunct distribution, relatively rare for a marine carcharhinid, is discussed. The Kuwait population of C. leiodon, including juveniles, is subject to fisheries by-catch and is in an area of extensive habitat alteration. As a result, C. leiodon is considered vulnerable, requiring urgent conservation action.
Colin A. Simpfendorfer - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Ecological Drivers of Shark Distributions along a Tropical Coastline
2016Co-Authors: Peter M. Yates, Andrew J. Tobin, Michelle R. Heupel, Colin A. SimpfendorferAbstract:As coastal species experience increasing anthropogenic pressures there is a growing need to characterise the ecological drivers of their abundance and habitat use, and understand how they may respond to changes in their environment. Accordingly, fishery-independent surveys were undertaken to investigate shark abundance along approximately 400 km of the tropical east coast of Australia. Generalised linear models were used to identify ecologi-cal drivers of the abundance of immature blacktip Carcharhinus tilstoni/Carcharhinus limba-tus, pigeye Carcharhinus amboinensis, and scalloped hammerhead Sphyrna lewini sharks. Results indicated general and species-specific patterns in abundance that were character-ised by a range of abiotic and biotic variables. Relationships with turbidity and salinity were similar across multiple species, highlighting the importance of these variables in the func-tioning of communal shark nurseries. In particular, turbid environments were especially im-portant for all species at typical oceanic salinities. Mangrove proximity, depth, and water temperature were also important; however, their influence varied between species. Ecologi-cal drivers may promote spatial diversity in habitat use along environmentally heteroge-neous coastlines and may therefore have important implications for population resilience
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Assessment of a data-limited, multi-species shark fishery in the Great Barrier Reef Marine Park and south-east Queensland
Fisheries Research, 2016Co-Authors: Alastair V. Harry, Jonathan J. Smart, Colin A. Simpfendorfer, Richard J. Saunders, Peter M. Yates, Andrew J. TobinAbstract:Abstract The status of five species of commercially exploited sharks within the Great Barrier Reef Marine Park (GBRMP) and south-east Queensland was assessed using a data-limited approach. Annual harvest rate, U , estimated empirically from tagging between 2011 and 2013, was compared with an analytically-derived proxy for optimal equilibrium harvest rate, U MSY Lim . Median estimates of U for three principal retained species, Australian blacktip shark, Carcharhinus tilstoni , spot-tail shark, Carcharhinus sorrah , and spinner shark, Carcharhinus brevipinna , were 0.10, 0.06 and 0.07 year −1 , respectively. Median U for two retained, non-target species, pigeye shark, Carcharhinus amboinensis and Australian sharpnose shark, Rhizoprionodon taylori , were 0.27 and 0.01 year −1 , respectively. For all species except the Australian blacktip the median ratio of U/U MSY Lim was U MSY Lim was low (0.04–0.07 year −1 ) and that U/U MSY Lim was likely to be >1. Harvest of the Australian blacktip shark above U MSY could place this species at a greater risk of localised depletion in parts of the GBRMP. Results of the study indicated that much higher catches, and presumably higher U , during the early 2000s were likely unsustainable. The unexpectedly high level of U on the pigeye shark indicated that output-based management controls may not have been effective in reducing harvest levels on all species, particularly those caught incidentally by other fishing sectors including the recreational sector.
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Spatio-Temporal Occurrence Patterns of Young Sharks in Tropical Coastal Waters
Estuaries and Coasts, 2015Co-Authors: Peter M. Yates, Andrew J. Tobin, Michelle R. Heupel, Colin A. SimpfendorferAbstract:Understanding spatio-temporal patterns in shark occurrence is critical for assessing the ecological role of a species, its vulnerability to human impacts and environmental change, and the efficacy of conservation and management strategies. Investigating these patterns can also develop an understanding of the functioning of coastal shark nurseries. In this context, we undertook a multi-year fisheries-independent survey of shark occurrence along a 400-km stretch of tropical coastline. Logistic regression was used to identify spatial, seasonal and inter-annual variations in the occurrence of neonate and young-of-the-year (YOY) blacktip Carcharhinus limbatus / Carcharhinus tilstoni , pigeye Carcharhinus amboinensis , scalloped hammerhead Sphyrna lewini and spot-tail Carcharhinus sorrah sharks. Results indicated interspecific variations in occurrence. Seasonal variations characterised the occurrence of YOY pigeye, YOY spot-tail and neonate blacktip sharks, whereas spatial variations were more pronounced for YOY blacktip and scalloped hammerhead sharks. These results suggested that the occurrence of young sharks may be more complex than would be predicted by the timing of parturition alone. In addition, spatial heterogeneity in occurrence suggested that proximate bays are likely to vary in terms of the services they provide to young sharks.
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Comparison of the reproductive ecology of two sympatric blacktip sharks (Carcharhinus limbatus and Carcharhinus tilstoni) off north-eastern Australia with species identification inferred from vertebral counts
Journal of fish biology, 2012Co-Authors: Alastair V. Harry, Andrew J. Tobin, Jennifer R. Ovenden, Jess A. T. Morgan, David Welch, Colin A. SimpfendorferAbstract:Precaudal vertebral counts were used to distinguish between 237 morphologically similar Carcharhinus limbatus and Carcharhinus tilstoni and were congruent with differences in reproductive ecology between the species. In addition to differing lengths at maturity and adult body size, the two species had asynchronous parturition, were born at different sizes and the relative frequencies of neonates differed in two coastal nursery areas. Despite evidence that hybridization can occur, these differences suggest the species are largely reproductively isolated.
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Occurrence of Carcharhinus isodon (Finetooth Shark) in
2007Co-Authors: Florida Bay, Tonya R. Wileyl, Colin A. SimpfendorferAbstract:Carcharhinus isodon (finetooth shark) is a migratory shark found in coastal waters of the southeastern United States and is well documented in the waters of north Florida in both the Gulf of Mexico and the Atlantic Ocean. The southern-
Dareen Almojil - One of the best experts on this subject based on the ideXlab platform.
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Weak population structure of the Spot-tail shark Carcharhinus sorrah and the Blacktip shark C. limbatus along the coasts of the Arabian Peninsula, Pakistan, and South Africa.
Ecology and Evolution, 2018Co-Authors: Dareen Almojil, Geremy Cliff, Julia L. Y. SpaetAbstract:The increase in demand for shark meat and fins has placed shark populations worldwide under high fishing pressure. In the Arabian region, the spot-tail shark Carcharhinus sorrah and the Blacktip shark Carcharhinus limbatus are among the most exploited species. In this study, we investigated the population genetic structure of C. sorrah (n = 327) along the coasts of the Arabian Peninsula and of C. limbatus (n = 525) along the Arabian coasts, Pakistan, and KwaZulu-Natal, South Africa, using microsatellite markers (15 and 11 loci, respectively). Our findings support weak population structure in both species. Carcharhinus sorrah exhibited a fine structure, subdividing the area into three groups. The first group comprises all samples from Bahrain, the second from the UAE and Yemen, and the third from Oman. Similarly, C. limbatus exhibited population subdivision into three groups. The first group, comprising samples from Bahrain and Kuwait, was highly differentiated from the second and third groups, comprising samples from Oman, Pakistan, the UAE, and Yemen; and South Africa and the Saudi Arabian Red Sea, respectively. Population divisions were supported by pairwise FST values and discriminant analysis of principal components (DAPC), but not by STRUCTURE. We suggest that the mostly low but significant pairwise FST values in our study are suggestive of fine population structure, which is possibly attributable to behavioral traits such as residency in C. sorrah and site fidelity and philopatry in C. limbatus. However, for all samples obtained from the northern parts of the Gulf (Bahrain and/or Kuwait) in both species, the higher but significant pairwise FST values could possibly be a result of founder effects during the Tethys Sea closure. Based on DAPC and FST results, we suggest each population to be treated as independent management unit, as conservation concerns emerge.