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Adam Barnett - One of the best experts on this subject based on the ideXlab platform.
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Evidence of historical isolation and genetic structuring among broadnose sevengill sharks (Notorynchus cepedianus) from the world’s major oceanic regions
Reviews in Fish Biology and Fisheries, 2021Co-Authors: Alicia C. J. Schmidt-roach, David A. Ebert, Adam Barnett, Christine C. Bruels, Adam D. Miller, Craig D. H. Sherman, Sebastian Schmidt-roach, Charlene Da Silva, Christopher G. Wilke, Craig ThorburnAbstract:Cosmopolitan marine pelagic species display variable patterns of population connectivity among the world’s major oceans. While this information is crucial for informing management, information is lacking for many ecologically important species, including apex predators. In this study we examine patterns of genetic structure in the broadnose sevengill shark, Notorynchus cepedianus across its global distribution. We estimate patterns of connectivity among broadnose sevengill shark populations from three major oceanic regions (South Atlantic, Oceania and Eastern Pacific) by contrasting mitochondrial and nuclear DNA haplotype frequencies. We also produced time calibrated Bayesian Inference phylogenetic reconstructions to analyses global phylogeographic patterns and estimate divergence times among distinctive shark lineages. Our results demonstrate significant genetic differentiation among oceanic regions ( Φ _ST = 0.9789, P
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evidence of historical isolation and genetic structuring among broadnose sevengill sharks Notorynchus cepedianus from the world s major oceanic regions
Reviews in Fish Biology and Fisheries, 2021Co-Authors: David A. Ebert, Adam Barnett, Christine C. Bruels, Adam D. Miller, Craig D. H. Sherman, Alicia C J SchmidtroachAbstract:Cosmopolitan marine pelagic species display variable patterns of population connectivity among the world’s major oceans. While this information is crucial for informing management, information is lacking for many ecologically important species, including apex predators. In this study we examine patterns of genetic structure in the broadnose sevengill shark, Notorynchus cepedianus across its global distribution. We estimate patterns of connectivity among broadnose sevengill shark populations from three major oceanic regions (South Atlantic, Oceania and Eastern Pacific) by contrasting mitochondrial and nuclear DNA haplotype frequencies. We also produced time calibrated Bayesian Inference phylogenetic reconstructions to analyses global phylogeographic patterns and estimate divergence times among distinctive shark lineages. Our results demonstrate significant genetic differentiation among oceanic regions (ΦST = 0.9789, P < 0.0001) and a lack of genetic structuring within regions (ΦST = − 0.007; P = 0.479). Time calibrated Bayesian Inference phylogenetic reconstructions indicate that the observed patterns of genetic structure among oceanic regions are historical, with regional populations estimated to have diverged from a common ancestor during the early to mid-Pleistocene. Our results indicate significant genetic structuring and a lack of gene flow among broadnose sevengill shark populations from the South Atlantic, Oceania and Eastern Pacific regions. Evidence of deep lineage divergences coinciding with the early to mid-Pleistocene suggests historical glacial cycling has contributed to the vicariant divergence of broadnose sevengill shark populations from different ocean basins. These finding will help inform global management of broadnose sevengill shark populations, and provides new insights into historical and contemporary evolutionary processes shaping populations of this ecologically important apex predator.
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Integrating acoustic telemetry into mark–recapture models to improve the precision of apparent survival and abundance estimates
Oecologia, 2015Co-Authors: Christine L. Dudgeon, Jayson M. Semmens, Kenneth H. Pollock, J. Matias Braccini, Adam BarnettAbstract:Capture–mark–recapture models are useful tools for estimating demographic parameters but often result in low precision when recapture rates are low. Low recapture rates are typical in many study systems including fishing-based studies. Incorporating auxiliary data into the models can improve precision and in some cases enable parameter estimation. Here, we present a novel application of acoustic telemetry for the estimation of apparent survival and abundance within capture–mark–recapture analysis using open population models. Our case study is based on simultaneously collecting longline fishing and acoustic telemetry data for a large mobile apex predator, the broadnose sevengill shark ( Notorhynchus cepedianus ), at a coastal site in Tasmania, Australia. Cormack–Jolly–Seber models showed that longline data alone had very low recapture rates while acoustic telemetry data for the same time period resulted in at least tenfold higher recapture rates. The apparent survival estimates were similar for the two datasets but the acoustic telemetry data showed much greater precision and enabled apparent survival parameter estimation for one dataset, which was inestimable using fishing data alone. Combined acoustic telemetry and longline data were incorporated into Jolly–Seber models using a Monte Carlo simulation approach. Abundance estimates were comparable to those with longline data only; however, the inclusion of acoustic telemetry data increased precision in the estimates. We conclude that acoustic telemetry is a useful tool for incorporating in capture–mark–recapture studies in the marine environment. Future studies should consider the application of acoustic telemetry within this framework when setting up the study design and sampling program.
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Integrating acoustic telemetry into mark-recapture models to improve the precision of apparent survival and abundance estimates
Oecologia, 2015Co-Authors: Christine L. Dudgeon, Jayson M. Semmens, Kenneth H. Pollock, J. Matias Braccini, Adam BarnettAbstract:Capture–mark–recapture models are useful tools for estimating demographic parameters but often result in low precision when recapture rates are low. Low recapture rates are typical in many study systems including fishing-based studies. Incorporating auxiliary data into the models can improve precision and in some cases enable parameter estimation. Here, we present a novel application of acoustic telemetry for the estimation of apparent survival and abundance within capture–mark–recapture analysis using open population models. Our case study is based on simultaneously collecting longline fishing and acoustic telemetry data for a large mobile apex predator, the broadnose sevengill shark (Notorhynchus cepedianus), at a coastal site in Tasmania, Australia. Cormack–Jolly–Seber models showed that longline data alone had very low recapture rates while acoustic telemetry data for the same time period resulted in at least tenfold higher recapture rates. The apparent survival estimates were similar for the two datasets but the acoustic telemetry data showed much greater precision and enabled apparent survival parameter estimation for one dataset, which was inestimable using fishing data alone. Combined acoustic telemetry and longline data were incorporated into Jolly–Seber models using a Monte Carlo simulation approach. Abundance estimates were comparable to those with longline data only; however, the inclusion of acoustic telemetry data increased precision in the estimates. We conclude that acoustic telemetry is a useful tool for incorporating in capture–mark–recapture studies in the marine environment. Future studies should consider the application of acoustic telemetry within this framework when setting up the study design and sampling program.
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Markov models and network analysis reveal sex-specific differences in the space-use of a coastal apex predator
Oikos, 2014Co-Authors: Kilian M. Stehfest, Adam Barnett, Toby A. Patterson, Jayson M. SemmensAbstract:Understanding the links between external variables such as habitat and interactions with conspecifics and animal space-use is fundamental to developing effective management measures. In the marine realm, automated acoustic tracking has become a widely used method for monitoring the movement of free-ranging animals, yet researchers generally lack robust methods for analysing the resulting spatial-usage data. In this study, acoustic tracking data from male and female broadnose sevengill sharks Notorynchus cepedianus, collected in a system of coastal embayments in southeast Tasmania were analyzed to examine sex-specific differences in the sharks' coastal space-use and test novel methods for the analysis of acoustic telemetry data. Sex-specific space-use of the broadnose sevengill shark from acoustic telemetry data was analysed in two ways: The recently proposed spatial network analysis of between-receiver movements was employed to identify sex-specific space-use patterns. To include the full breadth of temporal information held in the data, movements between receivers were furthermore considered as transitions between states of a Markov chain, with the resulting transition probability matrix allowing the ranking of the relative importance of different parts of the study area. Both spatial network and Markov chain analysis revealed sex-specific preferences of different sites within the study area. The identification of priority areas differed for the methods, due to the fact that in contrast to network analysis, our Markov chain approach preserves the chronological sequence of detections and accounts for both residency periods and movements. In addition to adding to our knowledge of the ecology of a globally distributed apex predator, this study presents a promising new step towards condensing the vast amounts of information collected with acoustic tracking technology into straightforward results which are directly applicable to the management and conservation of any species that meet the assumptions of our model.
Jayson M. Semmens - One of the best experts on this subject based on the ideXlab platform.
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Integrating acoustic telemetry into mark–recapture models to improve the precision of apparent survival and abundance estimates
Oecologia, 2015Co-Authors: Christine L. Dudgeon, Jayson M. Semmens, Kenneth H. Pollock, J. Matias Braccini, Adam BarnettAbstract:Capture–mark–recapture models are useful tools for estimating demographic parameters but often result in low precision when recapture rates are low. Low recapture rates are typical in many study systems including fishing-based studies. Incorporating auxiliary data into the models can improve precision and in some cases enable parameter estimation. Here, we present a novel application of acoustic telemetry for the estimation of apparent survival and abundance within capture–mark–recapture analysis using open population models. Our case study is based on simultaneously collecting longline fishing and acoustic telemetry data for a large mobile apex predator, the broadnose sevengill shark ( Notorhynchus cepedianus ), at a coastal site in Tasmania, Australia. Cormack–Jolly–Seber models showed that longline data alone had very low recapture rates while acoustic telemetry data for the same time period resulted in at least tenfold higher recapture rates. The apparent survival estimates were similar for the two datasets but the acoustic telemetry data showed much greater precision and enabled apparent survival parameter estimation for one dataset, which was inestimable using fishing data alone. Combined acoustic telemetry and longline data were incorporated into Jolly–Seber models using a Monte Carlo simulation approach. Abundance estimates were comparable to those with longline data only; however, the inclusion of acoustic telemetry data increased precision in the estimates. We conclude that acoustic telemetry is a useful tool for incorporating in capture–mark–recapture studies in the marine environment. Future studies should consider the application of acoustic telemetry within this framework when setting up the study design and sampling program.
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Integrating acoustic telemetry into mark-recapture models to improve the precision of apparent survival and abundance estimates
Oecologia, 2015Co-Authors: Christine L. Dudgeon, Jayson M. Semmens, Kenneth H. Pollock, J. Matias Braccini, Adam BarnettAbstract:Capture–mark–recapture models are useful tools for estimating demographic parameters but often result in low precision when recapture rates are low. Low recapture rates are typical in many study systems including fishing-based studies. Incorporating auxiliary data into the models can improve precision and in some cases enable parameter estimation. Here, we present a novel application of acoustic telemetry for the estimation of apparent survival and abundance within capture–mark–recapture analysis using open population models. Our case study is based on simultaneously collecting longline fishing and acoustic telemetry data for a large mobile apex predator, the broadnose sevengill shark (Notorhynchus cepedianus), at a coastal site in Tasmania, Australia. Cormack–Jolly–Seber models showed that longline data alone had very low recapture rates while acoustic telemetry data for the same time period resulted in at least tenfold higher recapture rates. The apparent survival estimates were similar for the two datasets but the acoustic telemetry data showed much greater precision and enabled apparent survival parameter estimation for one dataset, which was inestimable using fishing data alone. Combined acoustic telemetry and longline data were incorporated into Jolly–Seber models using a Monte Carlo simulation approach. Abundance estimates were comparable to those with longline data only; however, the inclusion of acoustic telemetry data increased precision in the estimates. We conclude that acoustic telemetry is a useful tool for incorporating in capture–mark–recapture studies in the marine environment. Future studies should consider the application of acoustic telemetry within this framework when setting up the study design and sampling program.
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Markov models and network analysis reveal sex-specific differences in the space-use of a coastal apex predator
Oikos, 2014Co-Authors: Kilian M. Stehfest, Adam Barnett, Toby A. Patterson, Jayson M. SemmensAbstract:Understanding the links between external variables such as habitat and interactions with conspecifics and animal space-use is fundamental to developing effective management measures. In the marine realm, automated acoustic tracking has become a widely used method for monitoring the movement of free-ranging animals, yet researchers generally lack robust methods for analysing the resulting spatial-usage data. In this study, acoustic tracking data from male and female broadnose sevengill sharks Notorynchus cepedianus, collected in a system of coastal embayments in southeast Tasmania were analyzed to examine sex-specific differences in the sharks' coastal space-use and test novel methods for the analysis of acoustic telemetry data. Sex-specific space-use of the broadnose sevengill shark from acoustic telemetry data was analysed in two ways: The recently proposed spatial network analysis of between-receiver movements was employed to identify sex-specific space-use patterns. To include the full breadth of temporal information held in the data, movements between receivers were furthermore considered as transitions between states of a Markov chain, with the resulting transition probability matrix allowing the ranking of the relative importance of different parts of the study area. Both spatial network and Markov chain analysis revealed sex-specific preferences of different sites within the study area. The identification of priority areas differed for the methods, due to the fact that in contrast to network analysis, our Markov chain approach preserves the chronological sequence of detections and accounts for both residency periods and movements. In addition to adding to our knowledge of the ecology of a globally distributed apex predator, this study presents a promising new step towards condensing the vast amounts of information collected with acoustic tracking technology into straightforward results which are directly applicable to the management and conservation of any species that meet the assumptions of our model.
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Intraspecific differences in movement, dive behavior and vertical habitat preferences of a key marine apex predator
Marine Ecology Progress Series, 2014Co-Authors: Kilian M. Stehfest, Adam Barnett, Toby A. Patterson, Jayson M. SemmensAbstract:Understanding the patterns of large-scale movements of highly mobile marine predators is essential to understanding the impacts of anthropogenic pressures on the animals and the ecosystems they frequent. The broadnose sevengill shark Notorynchus cepedianus is one of the most important apex predators in temperate coastal areas around the world, yet little is known of its seasonal large-scale movements. Five male and five female sevengill sharks were equipped with pop-up satellite archival tags (PSATs) in a coastal embayment in southern Tasmania, that collected depth and temperature data during winter, when the animals leave the coastal embayment, resulting in a dataset covering a total of 818 d. Animal tracks indicated that males moved northwards into warmer waters, whereas females remained in southern waters. Three of the females stayed in the Tasmanian coastal areas while the other two left, with one of them moving into deeper waters of up to 360 m depth at the southern edge of the Tasmanian shelf before returning to the Tasmanian coast. These sex-specific differences in large-scale movement could potentially lead to the differential exploitation of the sexes when the sharks leave the protected areas where they were tagged. Both males and females switched between diel vertical migration and reverse diel vertical migration over the course of their tracks and displayed oscillatory vertical movements, probably linked to foraging. These vertical movements persisted throughout the tracks, suggesting that sevengill sharks foraged continuously during their migration rather than switching between transiting and foraging modes.
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Fine-Scale Movements of the Broadnose Sevengill Shark and Its Main Prey, the Gummy Shark
2013Co-Authors: Adam Barnett, John D. Stevens, Kátya G. Abrantes, Barry D. Bruce, Jayson M. SemmensAbstract:Information on the fine-scale movement of predators and their prey is important to interpret foraging behaviours and activity patterns. An understanding of these behaviours will help determine predator-prey relationships and their effects on community dynamics. For instance understanding a predator’s movement behaviour may alter pre determined expectations of prey behaviour, as almost any aspect of the prey’s decisions from foraging to mating can be influenced by the risk of predation. Acoustic telemetry was used to study the fine-scale movement patterns of the Broadnose Sevengill shark Notorynchus cepedianus and its main prey, the Gummy shark Mustelus antarcticus, in a coastal bay of southeast Tasmania. Notorynchus cepedianus displayed distinct diel differences in activity patterns. During the day they stayed close to the substrate (sea floor) and were frequently inactive. At night, however, their swimming behaviour continually oscillated through the water column from the substrate to near surface. In contrast, M. antarcticus remained close to the substrate for the entire diel cycle, and showed similar movement patterns for day and night. For both species, the possibility that movement is related to foraging behaviour is discussed. For M. antarcticus, movement may possibly be linked to a diet of predominantly slow benthic prey. On several occasions, N. cepedianus carried out a sequence of burst speed events (increased rates of movement) that could be related to chasing prey. All burst speed events during the day were across the substrate, while at night these occurred in the water column. Overall, diel differences in water column use, along with th
David A. Ebert - One of the best experts on this subject based on the ideXlab platform.
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Evidence of historical isolation and genetic structuring among broadnose sevengill sharks (Notorynchus cepedianus) from the world’s major oceanic regions
Reviews in Fish Biology and Fisheries, 2021Co-Authors: Alicia C. J. Schmidt-roach, David A. Ebert, Adam Barnett, Christine C. Bruels, Adam D. Miller, Craig D. H. Sherman, Sebastian Schmidt-roach, Charlene Da Silva, Christopher G. Wilke, Craig ThorburnAbstract:Cosmopolitan marine pelagic species display variable patterns of population connectivity among the world’s major oceans. While this information is crucial for informing management, information is lacking for many ecologically important species, including apex predators. In this study we examine patterns of genetic structure in the broadnose sevengill shark, Notorynchus cepedianus across its global distribution. We estimate patterns of connectivity among broadnose sevengill shark populations from three major oceanic regions (South Atlantic, Oceania and Eastern Pacific) by contrasting mitochondrial and nuclear DNA haplotype frequencies. We also produced time calibrated Bayesian Inference phylogenetic reconstructions to analyses global phylogeographic patterns and estimate divergence times among distinctive shark lineages. Our results demonstrate significant genetic differentiation among oceanic regions ( Φ _ST = 0.9789, P
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evidence of historical isolation and genetic structuring among broadnose sevengill sharks Notorynchus cepedianus from the world s major oceanic regions
Reviews in Fish Biology and Fisheries, 2021Co-Authors: David A. Ebert, Adam Barnett, Christine C. Bruels, Adam D. Miller, Craig D. H. Sherman, Alicia C J SchmidtroachAbstract:Cosmopolitan marine pelagic species display variable patterns of population connectivity among the world’s major oceans. While this information is crucial for informing management, information is lacking for many ecologically important species, including apex predators. In this study we examine patterns of genetic structure in the broadnose sevengill shark, Notorynchus cepedianus across its global distribution. We estimate patterns of connectivity among broadnose sevengill shark populations from three major oceanic regions (South Atlantic, Oceania and Eastern Pacific) by contrasting mitochondrial and nuclear DNA haplotype frequencies. We also produced time calibrated Bayesian Inference phylogenetic reconstructions to analyses global phylogeographic patterns and estimate divergence times among distinctive shark lineages. Our results demonstrate significant genetic differentiation among oceanic regions (ΦST = 0.9789, P < 0.0001) and a lack of genetic structuring within regions (ΦST = − 0.007; P = 0.479). Time calibrated Bayesian Inference phylogenetic reconstructions indicate that the observed patterns of genetic structure among oceanic regions are historical, with regional populations estimated to have diverged from a common ancestor during the early to mid-Pleistocene. Our results indicate significant genetic structuring and a lack of gene flow among broadnose sevengill shark populations from the South Atlantic, Oceania and Eastern Pacific regions. Evidence of deep lineage divergences coinciding with the early to mid-Pleistocene suggests historical glacial cycling has contributed to the vicariant divergence of broadnose sevengill shark populations from different ocean basins. These finding will help inform global management of broadnose sevengill shark populations, and provides new insights into historical and contemporary evolutionary processes shaping populations of this ecologically important apex predator.
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First records of the seven‐gilled Notorynchus cepedianus and six‐gilled Hexanchus griseus sharks (Chondrichthyes: Hexanchiformes: Hexanchidae) found in the Galápagos Marine Reserve
Journal of fish biology, 2020Co-Authors: Salome Buglass, David A. Ebert, Shannon Nagy, Paulina Sepa, Alan Turchik, K L Bell, Fernando Rivera, Jonatha GiddensAbstract:This study reports the first records of cowsharks (Hexanchidae) in the Galapagos Islands, in particular Notorynchus cepedianus and Hexanchus griseus, observed between depths of 210 and 418 m on footage from free-falling autonomous deep-ocean cameras. These sightings provide new information on the habitat preferences and range distribution for N. cepedianus and the first records of H. griseus in Ecuadorian waters. The findings support the formulation of regional conservation strategies for these large apex predator species and highlight the limited biological knowledge of Galapagos' deep-water ecosystems.
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first records of the seven gilled Notorynchus cepedianus and six gilled hexanchus griseus sharks chondrichthyes hexanchiformes hexanchidae found in the galapagos marine reserve
Journal of Fish Biology, 2020Co-Authors: Salome Buglass, David A. Ebert, Shannon Nagy, Paulina Sepa, Alan Turchik, K L Bell, Fernando Rivera, Jonatha GiddensAbstract:This study reports the first records of cowsharks (Hexanchidae) in the Galapagos Islands, in particular Notorynchus cepedianus and Hexanchus griseus, observed between depths of 210 and 418 m on footage from free-falling autonomous deep ocean cameras. These sightings provide new information on the habitat preferences and range distribution for N. cepedianus, and the first records of H. griseus in Ecuadorian waters. Our findings support the formulation of regional conservation strategies for these large apex predator species, and highlight our limited biological knowledge of Galapagos' deep-water ecosystems. This article is protected by copyright. All rights reserved.
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first records of the seven gilled Notorynchus cepedianus and six gilled hexanchus griseus sharks chondrichthyes hexanchiformes hexanchidae found in the galapagos marine reserve
Journal of Fish Biology, 2020Co-Authors: Salome Buglass, David A. Ebert, Shannon Nagy, Paulina Sepa, Alan Turchik, K L Bell, Fernando Rivera, Jonatha GiddensAbstract:This study reports the first records of cowsharks (Hexanchidae) in the Galapagos Islands, in particular Notorynchus cepedianus and Hexanchus griseus, observed between depths of 210 and 418 m on footage from free-falling autonomous deep-ocean cameras. These sightings provide new information on the habitat preferences and range distribution for N. cepedianus and the first records of H. griseus in Ecuadorian waters. The findings support the formulation of regional conservation strategies for these large apex predator species and highlight the limited biological knowledge of Galapagos' deep-water ecosystems.
Alejo Joaquin Irigoyen - One of the best experts on this subject based on the ideXlab platform.
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Habitat use, seasonality and demography of the broadnose sevengill shark Notorynchus cepedianus in central Patagonia: Another piece of the puzzle
Austral Ecology, 2019Co-Authors: Alejo Joaquin Irigoyen, Gastón Andres Trobbiani, Nelson D. Bovcon, Agustín María De Wysiecki, Federico Argemi, A. J. JaureguizarAbstract:The habitat use, seasonality and demography of the broadnose sevengill shark Notorynchus cepedianus were investigated in central Patagonia, where a data gap exists for the species. Catch and effort and video‐derived indices indicated high relative abundance of sharks during warm months. Video stations revealed differences in the spatial use by sharks, being more frequently observed in the inner section of the bay. Complementary tagging efforts evidenced both a seasonal residence pattern and site fidelity between consecutive warm seasons. Juveniles outnumbered adults, which suggests that they may use the study area as a secondary nursing ground. Evidence from spontaneous regurgitation further suggests that prey abundance may be driving the seasonal occurrence of sharks in the region. This study allows for a more comprehensive understanding of the population structure and dynamics of sevengill sharks in the Southwest Atlantic. Abstract in Spanish is available with online material.
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Seasonality of immunological and health-state parameters of wild broadnose sevengill shark, Notorynchus cepedianus
Physiological and biochemical zoology : PBZ, 2019Co-Authors: Mc Sueiro, Alejo Joaquin Irigoyen, Federico Argemi, Ca Awruch, Maria G. PalaciosAbstract:AbstractSeasonal fluctuation in environmental parameters can influence immune responses of vertebrates and consequently influence their health and disease resistance. Although seasonality of immune...
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Habitat use, seasonality and demography of an apex predator: sevengill shark Notorynchus cepedianus in northern Patagonia
Marine Ecology Progress Series, 2018Co-Authors: Alejo Joaquin Irigoyen, Gastón Andres Trobbiani, Nelson D. Bovcon, Agustín María De Wysiecki, Federico Argemi, Ca Awruch, A. J. JaureguizarAbstract:ABSTRACT: Gaining insight on how species relate to their environment and other members of the trophic community is critical for their management. We investigated habitat use, seasonal patterns of abundance and population structure of the broadnose sevengill shark Notorynchus cepedianus in the marine temperate environment of a northern Patagonian bay (Argentina). We expected N. cepedianus to exhibit strong seasonality in the bay driven by the seasonal occurrence of important marine mammal prey. However, an alternative or complementary hypothesis arose from the possibility that N. cepedianus uses the area seasonally as mating grounds. To explore these hypotheses, a suite of baited remote underwater video stations and catch per unit effort data indices were used to estimate the seasonal relative abundance of the species inside the bay. Reproductive hormone levels were measured to determine reproductive status and maturity stages of the population. Results indicated that N. cepedianus uses the bay year-round, showing a peak abundance during spring when individuals aggregate, likely for feeding and mating purposes. Male and female total lengths at maturity were 170 and 190 cm, respectively. Contrary to other studies in the Southwest Atlantic, population composition remained similar throughout the seasons, with adults dominating over juveniles, and adult females prevailing in the population at all times. Considering the historical abundance decline recently reported for the species, protection and enforcement within protected areas across the Southwest Atlantic must remain of high priority in government initiatives.
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Depletion of trophy large-sized sharks populations of the Argentinean coast, south-western Atlantic: insights from fishers
Neotropical Ichthyology, 2016Co-Authors: Alejo Joaquin Irigoyen, Gastón Andres TrobbianiAbstract:Globally, sharks are impacted by a wide range of human activities, resulting in many populations being depleted. Trophy large-sized sharks of the Argentinean coast, the sand-tiger Carcharias taurus , the copper Carcharhinus brachyurus and the sevengill shark Notorynchus cepedianus are under intense sport and artisanal fishing since the 50's decade. However, the current and historical information for the assessment of its populations status is scarce. The aim of this work was to analyze the status of conservation of these species through the gathering of expert fishermen knowledge (FK) on semi-structured interviews. Abundance variation perception between the beginning and the end of fishermen careers revealed a critical status for the species study (means variation between -77 and -90 %). Furthermore, a best day's catch analysis reinforce this result in the case of the sand tiger shark. The school shark Galeorhinus galeus was included on this work with the objective of contrast FK with formal information available of catch-per-unit-effort (CPUE) time series. Both sources of information, despite are not comparable, shows declines ~ - 80%. The critical conservation situation of study species needs urgent management action, particularly for the san tiger shark which could became regionally extinct before the reaction of stakeholders occurs.
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patrones estacionales de abundancia en el golfo nuevo y migracion a lo largo de la plataforma argentina de cazones galeorhinus galeus linnaeus 1758 y gatopardos Notorynchus cepedianus peron 1807 argentina
Ecología Austral, 2015Co-Authors: Alejo Joaquin Irigoyen, Carolina Sibbald, Mariano Cuestas, Franco Cristiani, Gaston TrobbianiAbstract:Knowing the movement patterns of a certain species has substantial implications for its management and conservation, particularly in species that migrate hundreds to thousands of kilometers each year (e.g., many chondrichtyans). The objective of this paper was to study the seasonal abundance in the Golfo Nuevo and the migratory patterns of the school and sevengill shark across the Argentine shelf through a conventional capture-recapture plan. A total of 13 sevengill and 228 school sharks were tagged during a full annual cycle. From analysis of catch per unit effort we found that the species studied show a strong seasonal pattern in the Golfo Nuevo, with higher abundance from mid-Summer to Autumn and a lower one during Spring, when two school shark recaptures were registered north from the tagging site (38o and 40° S). These results represent the first direct evidence supporting the hypothesis of a unique school shark population in the South Atlantic Ocean. Nevertheless, the detection of male school sharks in the study site all year round indicates that at least part of the population could be spending the cold months of the year south of its distribution area. In the case of the sevengill shark, despite that few individuals were captured, the absence of the species during cold months suggest a seasonality similar to the school shark.
Ca Awruch - One of the best experts on this subject based on the ideXlab platform.
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Seasonality of immunological and health-state parameters of wild broadnose sevengill shark, Notorynchus cepedianus
Physiological and biochemical zoology : PBZ, 2019Co-Authors: Mc Sueiro, Alejo Joaquin Irigoyen, Federico Argemi, Ca Awruch, Maria G. PalaciosAbstract:AbstractSeasonal fluctuation in environmental parameters can influence immune responses of vertebrates and consequently influence their health and disease resistance. Although seasonality of immune...
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Habitat use, seasonality and demography of an apex predator: sevengill shark Notorynchus cepedianus in northern Patagonia
Marine Ecology Progress Series, 2018Co-Authors: Alejo Joaquin Irigoyen, Gastón Andres Trobbiani, Nelson D. Bovcon, Agustín María De Wysiecki, Federico Argemi, Ca Awruch, A. J. JaureguizarAbstract:ABSTRACT: Gaining insight on how species relate to their environment and other members of the trophic community is critical for their management. We investigated habitat use, seasonal patterns of abundance and population structure of the broadnose sevengill shark Notorynchus cepedianus in the marine temperate environment of a northern Patagonian bay (Argentina). We expected N. cepedianus to exhibit strong seasonality in the bay driven by the seasonal occurrence of important marine mammal prey. However, an alternative or complementary hypothesis arose from the possibility that N. cepedianus uses the area seasonally as mating grounds. To explore these hypotheses, a suite of baited remote underwater video stations and catch per unit effort data indices were used to estimate the seasonal relative abundance of the species inside the bay. Reproductive hormone levels were measured to determine reproductive status and maturity stages of the population. Results indicated that N. cepedianus uses the bay year-round, showing a peak abundance during spring when individuals aggregate, likely for feeding and mating purposes. Male and female total lengths at maturity were 170 and 190 cm, respectively. Contrary to other studies in the Southwest Atlantic, population composition remained similar throughout the seasons, with adults dominating over juveniles, and adult females prevailing in the population at all times. Considering the historical abundance decline recently reported for the species, protection and enforcement within protected areas across the Southwest Atlantic must remain of high priority in government initiatives.
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Seasonality of immunological and health-state parameters of wild broadnose sevengill shark, Notorynchus cepedianus
'University of Chicago Press', 2018Co-Authors: Mc Sueiro, Ca Awruch, Aj Irigoyen, Argemi F, Mg PalaciosAbstract:Seasonal fluctuation in environmental parameters can influenceimmune responses of vertebrates and consequently influencetheir health and disease resistance. Although seasonalityof immune function is well documented in a broadrange of vertebrate taxa, this information remains virtuallyunexplored in cartilaginous fish. Here we examine seasonalvariation in immune and general-health parameters of free livingadult broadnose sevengill sharks, Notorynchus cepedianus,along an annual cycle. We sampled sharks duringautumn/winter (i.e., coolest temperatures and nonreproductiveperiod) and spring/summer (i.e., warmest temperaturesand active reproductive period) and assessed aspects of immunity,general condition, and reproductive hormone levels.A seasonal influence was observed in some, but not all, parametersevaluated. Lower lymphocyte counts and higher heterophilcounts and granulocyte to lymphocyte (G∶L) ratios wereobserved in sharks sampled during autumn/winter than in thosesampled during spring/summer. On the other hand, total leukocytecounts, eosinophil counts, bacterial agglutination mediatedby natural antibodies, and hematocrit did not vary seasonally.The observed seasonal patterns could be explained as (1) greater levels of stress based on the G∶L ratio, (2) a sign of immunosuppressionor depressed immune investment based on the lowlymphocyte counts, and/or (3) a sign of ongoing infection basedon the higher heterophil counts in the colder seasons with respectto the warmer ones. In addition, the pattern is in line with thenotion that while acquired components are usually depressed bylower temperatures, some innate components might increase tooffset that reduction. Immune and health-state parameters weremostly independent of reproductive hormone levels, providinglittle support for a trade-off with reproduction. Overall, the observedseasonal pattern in immunity of broadnose sevengill sharkscould be related to changes in abiotic environmental condition,such as water temperature and photoperiod, although other factorssuch as availability of high-quality food may play a part
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Non-lethal assessment of the reproductive status of broadnose sevengill sharks (Notorynchus cepedianus) to determine the significance of habitat use in coastal areas
Conservation physiology, 2014Co-Authors: Ca Awruch, Susan M. Jones, Martín García Asorey, Adam BarnettAbstract:Identification of the importance of habitats that are frequently used by any species is essential to a complete understanding of the species' biology and to incorporate their ecological role into conservation and management programmes. In this context, the present study investigated whether Tasmanian coastal waters have any reproductive relevance for the broadnose sevengill shark (Notorynchus cepedianus). Although this species is a large coast-associated apex predator in these areas, there is a complete gap in understanding the role that these coastal systems could play in its reproduction. Reproductive hormones were used as a non-lethal method to address the reproductive biology of this species. Females seemed to have at least a bi-annual reproductive cycle, being pregnant for ∼1 year and spending at least 1 year non-pregnant, with the ovulatory cycle separated from gestation. Mature females were found to be ovulating, in the initial stages of pregnancy, resting or starting a new vitellogenic cycle. Notorynchus cepedianus did not use these coastal habitats for mating or as a pupping ground. Although the mating season was distinguished between September to April, only 22% of males showed mating scars during the peak of the mating period and no near-term pregnant females were observed. Thus, despite these coastal waters being an important foraging ground for this species, these areas did not have any reproductive relevance. In consequence, future management and conservation planning programmes need to identify whether there are other areas in Tasmania that play a critical role for reproductive purposes in this species. Finally, although previous studies have linked reproductive hormones with external examination of the gonads to validate the use of steroids as a non-lethal tool to address reproduction, the present study used this methodology without killing any animals. This has important implications for conservation programmes of threatened and endangered species worldwide where the methodology cannot be validated.
