The Bull Shark (Carcharhinus leucas) faces varying levels of exploitation around the world due to... more The Bull Shark (Carcharhinus leucas) faces varying levels of exploitation around the world due to its coastal distribution. Information regarding population connectivity is crucial to evaluate its conservation status and local fishing impacts. In this study, we sampled 922 putative Bull Sharks from 19 locations in the first global assessment of population structure of this cosmopolitan species. Using a recently developed DNA‐capture approach (DArTcap), samples were genotyped for 3400 nuclear markers. Additionally, full mitochondrial genomes of 384 Indo‐Pacific samples were sequenced. Reproductive isolation was found between and across ocean basins (eastern Pacific, western Atlantic, eastern Atlantic, Indo‐West Pacific) with distinct island populations in Japan and Fiji. Bull Sharks appear to maintain gene flow using shallow coastal waters as dispersal corridors, whereas large oceanic distances and historical land‐bridges act as barriers. Females tend to return to the same area for r...
Tab delimited text. On each line is indicated: the individual ID (ID); the oceanic basin where it... more Tab delimited text. On each line is indicated: the individual ID (ID); the oceanic basin where it was sampled (Oceanic basin); the sampling locality (Locality); the sampling locality code (Locality code); the date of sampling (Date of sampling); the sex of the individual (Sex); the total length of the individual in cm (TL (cm)); the mitochondrial haplotypes of the control region, the COI gene and the cytb gene (Haplotype CR, Haplotype COI, Haplotype cytb); the genotype of the individual at the 27 microsatellite loci used. Missing data are indicated by NA
Population genetics have been increasingly applied to study large sharks over the last decade. Wh... more Population genetics have been increasingly applied to study large sharks over the last decade. Whilst large shark species are often difficult to study with direct methods, improved knowledge is needed for both population management and conservation, especially for species vulnerable to anthropogenic and climatic impacts. The tiger shark, Galeocerdo cuvier, is an apex predator known to play important direct and indirect roles in tropical and sub-tropical marine ecosystems. While the global and Indo-West Pacific population genetic structure of this species has recently been investigated, questions remain over population structure and demographic history within the Western Indian (WIO) and within the Western Pacific Oceans (WPO). To address the knowledge gap in tiger shark regional population structures, the genetic diversity of 286 individuals sampled in seven localities was investigated using 27 microsatellite loci and three mitochondrial genes (CR, COI, cytb). A weak genetic differentiation was observed between the WIO and the WPO, suggesting high genetic connectivity. This result agrees with previous studies, and highlights the importance of the pelagic behaviour of this species to ensure gene flow. Using Approximate Bayesian Computation to couple information from both nuclear and mitochondrial markers, evidence of a recent bottleneck in the Holocene (2,000-3,000 years ago) was found, which is the most probable cause for the low genetic diversity observed. A contemporary effective population size as low as 111 [43,369] was estimated during the bottleneck. Together, these results indicate low genetic diversity that may reflect a vulnerable population sensitive to regional pressures. Conservation measures are thus needed to protect a species that is classified as Near Threatened
SUMMARY Seychelles supports around three million nesting pairs of sooty terns. However, there hav... more SUMMARY Seychelles supports around three million nesting pairs of sooty terns. However, there have been recent declines and the colonies continue to face ongoing threats from habitat change and excessive commercial harvesting of their eggs, as well as potential threats by commercial fishing and climate change. A possible method to counter these threats is to re-establish breeding colonies on islands from which they have disappeared. An attempt was made to attract birds to a previously occupied island through habitat management, decoy birds and playback of recorded sooty tern calls. Habitat preparation involved predator eradication and tree removal to provide open ground with bare sandy areas and low herb vegetation. Overflying birds were attracted by broadcast calls, with some circling over and landing among the decoys. Large three-dimensional plastic models were superior to other models presented. This study demonstrated that large numbers of birds can be attracted by these means a...
Western Indian Ocean journal of marine science, 2013
On the morning of 25 September 2013, a large female bull shark, Carcharhinus leucas , was landed ... more On the morning of 25 September 2013, a large female bull shark, Carcharhinus leucas , was landed in Port Victoria, Seychelles. It had been caught on an anchored long line set the previous evening, within 100 m of the main fishing quay. The female exhibited an unusually large girth for this heavy-set species. The shark was photographed (Fig. 1a) and morphological measurements taken. On dissection the shark was found to be carrying 14 late stage embryos which were likewise measured and photographed (Fig. 1b). The adult female measured 276 cm total length (TL). The 14 pups, consisting of seven males and seven females, had a mean TL of 69 cm and a size range of 65-71cm TL. The pups’ teeth had yet to emerge from the gums suggesting parturition was not imminent. Leading international data sources, Fishbase (Froese & Pauly, 2013) and the IUCN Red List (Simpfendorfer & Burgess, 2009), cite the maximum litter size for C. leucas as 13 pups. Review of the authoritative compendia and literatur...
Population genetics has been increasingly applied to study large sharks over the last decade. Whi... more Population genetics has been increasingly applied to study large sharks over the last decade. Whilst large shark species are often difficult to study with direct methods, improved knowledge is needed for both population management and conservation, especially for species vulnerable to anthropogenic and climatic impacts. The tiger shark, Galeocerdo cuvier, is an apex predator known to play important direct and indirect roles in tropical and subtropical marine ecosystems. While the global and Indo‐West Pacific population genetic structure of this species has recently been investigated, questions remain over population structure and demographic history within the western Indian (WIO) and within the western Pacific Oceans (WPO). To address the knowledge gap in tiger shark regional population structures, the genetic diversity of 286 individuals sampled in seven localities was investigated using 27 microsatellite loci and three mitochondrial genes (CR, COI, and cytb). A weak genetic diffe...
Seychelles supports around three million nesting pairs of sooty terns but there have been recent ... more Seychelles supports around three million nesting pairs of sooty terns but there have been recent declines and the colonies continue to face actual threats of habitat change and excessive commercial harvesting of their eggs, and potential threats caused by commercial fishing and climate change. A possible method to counter these threats is to re-establish breeding colonies on islands from which they have disappeared. This study attempted to achieve this through habitat creation and attraction of birds to the prepared colony site using behavioural attractants – playback of recorded calls and presentation of models. Habitat preparation involved predator eradication and tree removal to provide a 2 ha area of open ground with bare sandy areas and low herb vegetation. Broadcast calls were essential to attract overflying birds. Once attracted, birds circled over and landed among the models. Large 3-dimensional plastic models were superior to other models presented. The study has demonstrat...
Seychelles Black Paradise-flycatcher Terpsiphone corvina is found almost exclusively on the 10 km... more Seychelles Black Paradise-flycatcher Terpsiphone corvina is found almost exclusively on the 10 km2 island of La Digue. It is currently considered the second rarest endemic bird in the Seychelles, using the criteria of total population and number of discrete populations. Research reassessing the habitat requirements of the flycatcher was conducted on La Digue from 1999 to 2001. This work was conducted in parallel with assessment and ranking of the suitability of medium-sized islands of the inner Seychelles archipelago for avian ecosystem restoration, using biological, geographical and anthropogenic criteria. Predator eradications on several islands have led to a reduction in the range of alien predators, and future eradications are planned. These developments combined with the findings of recent ecological research and a novel assessment of many islands in the archipelago have led to the opportunity for a reassessment of conservation options for Seychelles Black Paradise-flycatcher. ...
The Bull Shark (Carcharhinus leucas) faces varying levels of exploitation around the world due to... more The Bull Shark (Carcharhinus leucas) faces varying levels of exploitation around the world due to its coastal distribution. Information regarding population connectivity is crucial to evaluate its conservation status and local fishing impacts. In this study, we sampled 922 putative Bull Sharks from 19 locations in the first global assessment of population structure of this cosmopolitan species. Using a recently developed DNA‐capture approach (DArTcap), samples were genotyped for 3400 nuclear markers. Additionally, full mitochondrial genomes of 384 Indo‐Pacific samples were sequenced. Reproductive isolation was found between and across ocean basins (eastern Pacific, western Atlantic, eastern Atlantic, Indo‐West Pacific) with distinct island populations in Japan and Fiji. Bull Sharks appear to maintain gene flow using shallow coastal waters as dispersal corridors, whereas large oceanic distances and historical land‐bridges act as barriers. Females tend to return to the same area for r...
Tab delimited text. On each line is indicated: the individual ID (ID); the oceanic basin where it... more Tab delimited text. On each line is indicated: the individual ID (ID); the oceanic basin where it was sampled (Oceanic basin); the sampling locality (Locality); the sampling locality code (Locality code); the date of sampling (Date of sampling); the sex of the individual (Sex); the total length of the individual in cm (TL (cm)); the mitochondrial haplotypes of the control region, the COI gene and the cytb gene (Haplotype CR, Haplotype COI, Haplotype cytb); the genotype of the individual at the 27 microsatellite loci used. Missing data are indicated by NA
Population genetics have been increasingly applied to study large sharks over the last decade. Wh... more Population genetics have been increasingly applied to study large sharks over the last decade. Whilst large shark species are often difficult to study with direct methods, improved knowledge is needed for both population management and conservation, especially for species vulnerable to anthropogenic and climatic impacts. The tiger shark, Galeocerdo cuvier, is an apex predator known to play important direct and indirect roles in tropical and sub-tropical marine ecosystems. While the global and Indo-West Pacific population genetic structure of this species has recently been investigated, questions remain over population structure and demographic history within the Western Indian (WIO) and within the Western Pacific Oceans (WPO). To address the knowledge gap in tiger shark regional population structures, the genetic diversity of 286 individuals sampled in seven localities was investigated using 27 microsatellite loci and three mitochondrial genes (CR, COI, cytb). A weak genetic differentiation was observed between the WIO and the WPO, suggesting high genetic connectivity. This result agrees with previous studies, and highlights the importance of the pelagic behaviour of this species to ensure gene flow. Using Approximate Bayesian Computation to couple information from both nuclear and mitochondrial markers, evidence of a recent bottleneck in the Holocene (2,000-3,000 years ago) was found, which is the most probable cause for the low genetic diversity observed. A contemporary effective population size as low as 111 [43,369] was estimated during the bottleneck. Together, these results indicate low genetic diversity that may reflect a vulnerable population sensitive to regional pressures. Conservation measures are thus needed to protect a species that is classified as Near Threatened
SUMMARY Seychelles supports around three million nesting pairs of sooty terns. However, there hav... more SUMMARY Seychelles supports around three million nesting pairs of sooty terns. However, there have been recent declines and the colonies continue to face ongoing threats from habitat change and excessive commercial harvesting of their eggs, as well as potential threats by commercial fishing and climate change. A possible method to counter these threats is to re-establish breeding colonies on islands from which they have disappeared. An attempt was made to attract birds to a previously occupied island through habitat management, decoy birds and playback of recorded sooty tern calls. Habitat preparation involved predator eradication and tree removal to provide open ground with bare sandy areas and low herb vegetation. Overflying birds were attracted by broadcast calls, with some circling over and landing among the decoys. Large three-dimensional plastic models were superior to other models presented. This study demonstrated that large numbers of birds can be attracted by these means a...
Western Indian Ocean journal of marine science, 2013
On the morning of 25 September 2013, a large female bull shark, Carcharhinus leucas , was landed ... more On the morning of 25 September 2013, a large female bull shark, Carcharhinus leucas , was landed in Port Victoria, Seychelles. It had been caught on an anchored long line set the previous evening, within 100 m of the main fishing quay. The female exhibited an unusually large girth for this heavy-set species. The shark was photographed (Fig. 1a) and morphological measurements taken. On dissection the shark was found to be carrying 14 late stage embryos which were likewise measured and photographed (Fig. 1b). The adult female measured 276 cm total length (TL). The 14 pups, consisting of seven males and seven females, had a mean TL of 69 cm and a size range of 65-71cm TL. The pups’ teeth had yet to emerge from the gums suggesting parturition was not imminent. Leading international data sources, Fishbase (Froese & Pauly, 2013) and the IUCN Red List (Simpfendorfer & Burgess, 2009), cite the maximum litter size for C. leucas as 13 pups. Review of the authoritative compendia and literatur...
Population genetics has been increasingly applied to study large sharks over the last decade. Whi... more Population genetics has been increasingly applied to study large sharks over the last decade. Whilst large shark species are often difficult to study with direct methods, improved knowledge is needed for both population management and conservation, especially for species vulnerable to anthropogenic and climatic impacts. The tiger shark, Galeocerdo cuvier, is an apex predator known to play important direct and indirect roles in tropical and subtropical marine ecosystems. While the global and Indo‐West Pacific population genetic structure of this species has recently been investigated, questions remain over population structure and demographic history within the western Indian (WIO) and within the western Pacific Oceans (WPO). To address the knowledge gap in tiger shark regional population structures, the genetic diversity of 286 individuals sampled in seven localities was investigated using 27 microsatellite loci and three mitochondrial genes (CR, COI, and cytb). A weak genetic diffe...
Seychelles supports around three million nesting pairs of sooty terns but there have been recent ... more Seychelles supports around three million nesting pairs of sooty terns but there have been recent declines and the colonies continue to face actual threats of habitat change and excessive commercial harvesting of their eggs, and potential threats caused by commercial fishing and climate change. A possible method to counter these threats is to re-establish breeding colonies on islands from which they have disappeared. This study attempted to achieve this through habitat creation and attraction of birds to the prepared colony site using behavioural attractants – playback of recorded calls and presentation of models. Habitat preparation involved predator eradication and tree removal to provide a 2 ha area of open ground with bare sandy areas and low herb vegetation. Broadcast calls were essential to attract overflying birds. Once attracted, birds circled over and landed among the models. Large 3-dimensional plastic models were superior to other models presented. The study has demonstrat...
Seychelles Black Paradise-flycatcher Terpsiphone corvina is found almost exclusively on the 10 km... more Seychelles Black Paradise-flycatcher Terpsiphone corvina is found almost exclusively on the 10 km2 island of La Digue. It is currently considered the second rarest endemic bird in the Seychelles, using the criteria of total population and number of discrete populations. Research reassessing the habitat requirements of the flycatcher was conducted on La Digue from 1999 to 2001. This work was conducted in parallel with assessment and ranking of the suitability of medium-sized islands of the inner Seychelles archipelago for avian ecosystem restoration, using biological, geographical and anthropogenic criteria. Predator eradications on several islands have led to a reduction in the range of alien predators, and future eradications are planned. These developments combined with the findings of recent ecological research and a novel assessment of many islands in the archipelago have led to the opportunity for a reassessment of conservation options for Seychelles Black Paradise-flycatcher. ...
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