The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Barbara A Block - One of the best experts on this subject based on the ideXlab platform.
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stable isotope analysis challenges wasp waist food web assumptions in an upwelling Pelagic Ecosystem
Scientific Reports, 2012Co-Authors: Daniel J Madigan, Aaron B Carlisle, Heidi Dewar, Owyn E Snodgrass, Steven Y Litvin, Fiorenza Micheli, Barbara A BlockAbstract:Eastern boundary currents are often described as ‘wasp-waist’ Ecosystems in which one or few mid-level forage species support a high diversity of larger predators that are highly susceptible to fluctuations in prey biomass. The assumption of wasp-waist control has not been empirically tested in all such Ecosystems. This study used stable isotope analysis to test the hypothesis of wasp-waist control in the southern California Current large marine Ecosystem (CCLME). We analyzed prey and predator tissue for δ13C and δ15N and used Bayesian mixing models to provide estimates of CCLME trophic dynamics from 2007–2010. Our results show high omnivory, planktivory by some predators, and a higher degree of trophic connectivity than that suggested by the wasp-waist model. Based on this study period, wasp-waist models oversimplify trophic dynamics within the CCLME and potentially other upwelling, Pelagic Ecosystems. Higher trophic connectivity in the CCLME likely increases Ecosystem stability and resilience to perturbations.
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case study white shark movements in the north pacific Pelagic Ecosystem
2009Co-Authors: Andre Boustany, Kevin C Weng, Scot D Anderson, Peter Pyle, Barbara A BlockAbstract:The advent of novel electronic tracking technologies has allowed researchers to study the movements of ocean animals in their natural environment. Pop-up tagging of adult white sharks off the coast of central California provided insight into the movement patterns and environmental preferences of these sharks in the North Pacifi c Ocean. Tagged white sharks spent long periods, up to 8 months, in the Pelagic Ecosystem and far from land. While offshore, sharks experienced a wide range of depths and temperatures. The purpose of these offshore excursions remains unknown, but further tagging over wider size ranges
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Sharks of the Open Ocean: Biology, Fisheries and Conservation - Case Study: White Shark Movements in the North Pacific Pelagic Ecosystem
Sharks of the Open Ocean, 2009Co-Authors: Andre Boustany, Kevin C Weng, Scot D Anderson, Peter Pyle, Barbara A BlockAbstract:The advent of novel electronic tracking technologies has allowed researchers to study the movements of ocean animals in their natural environment. Pop-up tagging of adult white sharks off the coast of central California provided insight into the movement patterns and environmental preferences of these sharks in the North Pacifi c Ocean. Tagged white sharks spent long periods, up to 8 months, in the Pelagic Ecosystem and far from land. While offshore, sharks experienced a wide range of depths and temperatures. The purpose of these offshore excursions remains unknown, but further tagging over wider size ranges
M E Baird - One of the best experts on this subject based on the ideXlab platform.
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limits to prediction in a size resolved Pelagic Ecosystem model
Journal of Plankton Research, 2010Co-Authors: M E BairdAbstract:approximately halve the effect of growth of initial condition perturbations on prediction. Further numerical experiments are undertaken with the mean body weight at which size-classes are solved perturbed randomly with a standard deviation of 0.15, 0.015, 0.0015 and 0.00015 of the unperturbed body weight. The greatest effect, which dominates the s ¼ 0.15 and 0.015 ensembles, occurs when the perturbations of the size-class distribution add and/or remove predator‐prey links. These results provide a cautionary warning for the prediction of instantaneous states using complex Pelagic Ecosystems that are displaced from a stable oscillation and for which biological state is not dominated by physical processes.
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Limits to prediction in a size-resolved Pelagic Ecosystem model
Journal of Plankton Research, 2010Co-Authors: M E BairdAbstract:A size-resolved Pelagic Ecosystem model has been developed based on a continuous (with size) set of model equations and using allometric relationships to specify size-dependent physiological rates. Numerical experiments with identical model equations but different initial conditions and size-class distributions are used to investigate inherent limits to prediction of instantaneous state from an initial condition. The simulations have relatively constant physical forcings, such as solar radiation, to emphasize the dynamical properties of the size-resolved model. Initial condition experiments show that perturbations of 1, 0.1, 0.01, 0.001 and 0.0001% of the initial biomass of individual size-classes from a Hat size spectrum lead to equal spread of model trajectories. The greatest divergence of trajectories occurs when a 2.7 mu m equivalent spherical radius phytoplankton size-class blooms. This divergence has a finite-time Lyapunov exponent of 0.21 day(-1) a prediction time of 33 days for a precision of 10(-3) mol N m(-3). Large member ensembles can approximately halve the effect of growth of initial condition perturbations on prediction. Further numerical experiments are undertaken with the mean body weight at which size-classes are solved perturbed randomly with a standard deviation of 0.15, 0.015, 0.0015 and 0.00015 of the unperturbed body weight. The greatest effect, which dominates the sigma = 0.15 and 0.015 ensembles, occurs when the perturbations of the size-class distribution add and/or remove predator-prey links. These results provide a cautionary warning for the prediction of instantaneous states using complex Pelagic Ecosystems that are displaced from a stable oscillation and for which biological state is not dominated by physical processes.
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a size resolved Pelagic Ecosystem model
Ecological Modelling, 2007Co-Authors: M E Baird, Iain M. SuthersAbstract:A size-resolved Pelagic Ecosystem model is developed using descriptions of physical lim- its to biological processes and allometric relationships to determine physiological rates. The model contains three functional groups: phytoplankton, protozoans and metazoans— requiring three separately resolved size distributions. Within each functional group the size-resolution of the model can be altered without changing the model parameters, which are the coefficients of the allometric relationships, or changing the model equations, which are characteristic of each functional group. This approach allows the number of size-classes to be varied, and for a convergence of output with increasing resolution to be achieved. In this paper, a biological configuration is analysed composed of 62 size-classes doubling in biomass between classes and ranging in volume over 19 orders of magnitude from 0.32m3,
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A size-resolved Pelagic Ecosystem model
Ecological Modelling, 2007Co-Authors: M E Baird, Iain M. SuthersAbstract:A size-resolved Pelagic Ecosystem model is developed using descriptions\nof physical limits to biological processes and allometric relationships\nto determine physiological rates. The model contains three functional\ngroups: phytoplankton, protozoans and metazoans–requiring three\nseparately resolved size distributions. Within each functional group\nthe size-resolution of the model can be altered without changing\nthe model parameters, which are the coefficients of the allometric\nrelationships, or changing the model equations, which are characteristic\nof each functional group. This approach allows the number of size-classes\nto be varied, and for a convergence of output with increasing resolution\nto be achieved. In this paper, a biological configuration is analysed\ncomposed of 62 size-classes doubling in biomass between classes and\nranging in volume over 19 orders of magnitude from 0.32[thin space]\nm3, representative of the cyanobacteria Prochlorococcus sp., to 2.05x1018\n[thin space] m3, representative of a metazoan size-class with an\nequivalent spherical radius of 78.8[thin space]cm. The phytoplankton\nsize-classes extend through the first 17 size-classes, protozoan\nfrom the 9th to 21st, and metazoan from the 18th to 62nd. The size-resolved\nmodel is coupled to a 1D model of the oceanic mixed layer. Numerical\nexperiments show the size-resolved model is relatively insensitive\nto size resolution and higher order closure terms with the 62 size-class\nconfiguration, but is sensitive to initial conditions. The model\noutput is most sensitive to the parameter describing the smallest\nsize-class of prey available to a metazoan predator, and the nitrogen\ncontent of a phytoplankton cell. The concentration of DIN and biomass\nof protozoa are in general the most sensitive model outputs. These\nexperiments provide a background understanding for further application\nof the size-resolved Pelagic Ecosystem model.
LAURENT BERGER - One of the best experts on this subject based on the ideXlab platform.
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the pelgas survey ship based integrated monitoring of the bay of biscay Pelagic Ecosystem
Progress in Oceanography, 2017Co-Authors: Mathieu Doray, Jean Baptiste Romagnan, Florence Sanchez, Jerome Spitz, Martin Huret, Pierre Petitgas, Erwan Duhamel, Matthieu Authier, Christine Dupuy, LAURENT BERGERAbstract:The Pelagiques Gascogne (PELGAS) integrated survey has been developed by a multidisciplinary team of Ifremer and La Rochelle University scientists since 2000, joined by commercial fishermen in 2007. Its initial focus was to assess the biomass and predict the recruitment success of anchovy in the Bay of Biscay in spring. Taking advantage of the space and versatility of R/V Thalassa II, sampling has been progressively extended to other Ecosystem components. PELGAS therefore further developed the second objective of monitoring and studying the dynamic and diverse Biscay Pelagic Ecosystem in springtime. The PELGAS survey model has allowed for the establishment of a long-term time-series of spatially-explicit data of the Bay of Biscay Pelagic Ecosystem since the year 2000. Main sampled components of the targeted Ecosystem are: hydrology, phytoplankton, mesozooplankton, fish and megafauna. The survey now provides two main Ecosystem products: standard raster maps of Ecosystem parameters, and a time series dataset of indicators of the Bay of Biscay Pelagic Ecosystem state. They are used to inform fish stock and Ecosystem-based management, and support Ecosystem research. The present paper introduces the PELGAS survey, as a practical example of an integrated, vessel-based, Ecosystem survey. The evolution of the PELGAS scientific team and sampling protocols are presented and analysed, to outline factors crucial to the success of the survey. Data and results derived from PELGAS are reviewed, to exemplify scientific questions that can be tackled by integrated Ecosystem survey data. Advantages and challenges of the survey are discussed and put into the context of marine Ecosystem surveys in the European Marine Strategy Framework Directive and the Common Fisheries Policy.
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The PELGAS survey: Ship-based integrated monitoring of the Bay of Biscay Pelagic Ecosystem
Progress in Oceanography, 2017Co-Authors: Mathieu Doray, Jean Baptiste Romagnan, Florence Sanchez, Corinne Dupuy, Jerome Spitz, Martin Huret, Pierre Petitgas, Erwan Duhamel, Matthieu Authier, LAURENT BERGERAbstract:The Pélagiques Gascogne (PELGAS) integrated survey has been developed by a multidisciplinary team of Ifremer and La Rochelle University scientists since 2000, joined by commercial fishermen in 2007. Its initial focus was to assess the biomass and predict the recruitment success of anchovy in the Bay of Biscay in spring. Taking advantage of the space and versatility of R/V Thalassa II, sampling has been progressively extended to other Ecosystem components. PELGAS therefore further developed the second objective of monitoring and studying the dynamic and diverse Biscay Pelagic Ecosystem in springtime. The PELGAS survey model has allowed for the establishment of a long-term time-series of spatially-explicit data of the Bay of Biscay Pelagic Ecosystem since the year 2000. Main sampled components of the targeted Ecosystem are: hydrology, phytoplankton, mesozooplankton, fish and megafauna. The survey now provides two main Ecosystem products: standard raster maps of Ecosystem parameters, and a time series dataset of indicators of the Bay of Biscay Pelagic Ecosystem state. They are used to inform fish stock and Ecosystem-based management, and support Ecosystem research. The present paper introduces the PELGAS survey, as a practical example of an integrated, vessel-based, Ecosystem survey. The evolution of the PELGAS scientific team and sampling protocols are presented and analysed, to outline factors crucial to the success of the survey. Data and results derived from PELGAS are reviewed, to exemplify scientific questions that can be tackled by integrated Ecosystem survey data. Advantages and challenges of the survey are discussed and put into the context of marine Ecosystem surveys in the European Marine Strategy Framework Directive and the Common Fisheries Policy.
Carl J Walters - One of the best experts on this subject based on the ideXlab platform.
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physical forcing and the dynamics of the Pelagic Ecosystem in the eastern tropical pacific simulations with enso scale and global warming climate drivers
Canadian Journal of Fisheries and Aquatic Sciences, 2003Co-Authors: George M Watters, Robert J Olson, Robert C Francis, Paul C Fiedler, Jeffrey J Polovina, Stephen B Reilly, Kerim Aydin, Christofer H Boggs, Timothy E Essington, Carl J WaltersAbstract:We used a model of the Pelagic Ecosystem in the eastern tropical Pacific Ocean to explore how climate variation at El Nino Southern Oscillation (ENSO) scales might affect animals at middle and upper trophic levels. We developed two physical-forcing scenarios: (1) physical effects on phytoplankton biomass and (2) simultaneous physical effects on phytoplankton biomass and predator recruitment. We simulated the effects of climate-anomaly pulses, climate cycles, and global warming. Pulses caused oscillations to propagate through the Ecosystem; cycles affected the shapes of these oscillations; and warming caused trends. We concluded that biomass trajectories of single populations at middle and upper trophic levels cannot be used to detect bottom-up effects, that direct physical effects on predator recruitment can be the dominant source of interannual variability in Pelagic Ecosystems, that such direct effects may dampen top-down control by fisheries, and that predictions about the effects of climate change m...
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the role of sharks and longline fisheries in a Pelagic Ecosystem of the central pacific
Ecosystems, 2002Co-Authors: James F Kitchell, Christofer H Boggs, Timothy E Essington, Daniel E Schindler, Carl J WaltersAbstract:The increased exploitation of Pelagic sharks by longline fisheries raised questions about changes in the food webs that include sharks as apex predators. We used a version of Ecopath/Ecosim models to evaluate changes in trophic interactions due to shark exploitation in the Central North Pacific. Fisheries targeted on blue sharks tend to produce compensatory responses that favor other shark species and billfishes, but they have only modest effects on the majority of food web components. Modest levels of intraguild predation (adult sharks that eat juvenile sharks) produce strong, nonlinear responses in shark populations. In general, analysis of the Central North Pacific model reveals that sharks are not keystone predators, but that increases in longline fisheries can have profound effects on the food webs that support sharks.
Mathieu Doray - One of the best experts on this subject based on the ideXlab platform.
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Direct assessment of small Pelagic fish by the PELGAS14 acoustic survey
2020Co-Authors: Erwan Duhamel, Mathieu Doray, Martin Huret, Matthieu Authier, Thomas GestinAbstract:Acoustic surveys are carried out every year in the Bay of Biscay in spring onboard the French research vessel Thalassa. The objective of PELGAS surveys is to study the abundance and distribution of Pelagic fish in the Bay of Biscay. The main target species are anchovy and sardine but they are considered in a multi-specific context and within an Ecosystemic approach as they are located in the centre of Pelagic Ecosystem.
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the pelgas survey ship based integrated monitoring of the bay of biscay Pelagic Ecosystem
Progress in Oceanography, 2017Co-Authors: Mathieu Doray, Jean Baptiste Romagnan, Florence Sanchez, Jerome Spitz, Martin Huret, Pierre Petitgas, Erwan Duhamel, Matthieu Authier, Christine Dupuy, LAURENT BERGERAbstract:The Pelagiques Gascogne (PELGAS) integrated survey has been developed by a multidisciplinary team of Ifremer and La Rochelle University scientists since 2000, joined by commercial fishermen in 2007. Its initial focus was to assess the biomass and predict the recruitment success of anchovy in the Bay of Biscay in spring. Taking advantage of the space and versatility of R/V Thalassa II, sampling has been progressively extended to other Ecosystem components. PELGAS therefore further developed the second objective of monitoring and studying the dynamic and diverse Biscay Pelagic Ecosystem in springtime. The PELGAS survey model has allowed for the establishment of a long-term time-series of spatially-explicit data of the Bay of Biscay Pelagic Ecosystem since the year 2000. Main sampled components of the targeted Ecosystem are: hydrology, phytoplankton, mesozooplankton, fish and megafauna. The survey now provides two main Ecosystem products: standard raster maps of Ecosystem parameters, and a time series dataset of indicators of the Bay of Biscay Pelagic Ecosystem state. They are used to inform fish stock and Ecosystem-based management, and support Ecosystem research. The present paper introduces the PELGAS survey, as a practical example of an integrated, vessel-based, Ecosystem survey. The evolution of the PELGAS scientific team and sampling protocols are presented and analysed, to outline factors crucial to the success of the survey. Data and results derived from PELGAS are reviewed, to exemplify scientific questions that can be tackled by integrated Ecosystem survey data. Advantages and challenges of the survey are discussed and put into the context of marine Ecosystem surveys in the European Marine Strategy Framework Directive and the Common Fisheries Policy.
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The PELGAS survey: Ship-based integrated monitoring of the Bay of Biscay Pelagic Ecosystem
Progress in Oceanography, 2017Co-Authors: Mathieu Doray, Jean Baptiste Romagnan, Florence Sanchez, Corinne Dupuy, Jerome Spitz, Martin Huret, Pierre Petitgas, Erwan Duhamel, Matthieu Authier, LAURENT BERGERAbstract:The Pélagiques Gascogne (PELGAS) integrated survey has been developed by a multidisciplinary team of Ifremer and La Rochelle University scientists since 2000, joined by commercial fishermen in 2007. Its initial focus was to assess the biomass and predict the recruitment success of anchovy in the Bay of Biscay in spring. Taking advantage of the space and versatility of R/V Thalassa II, sampling has been progressively extended to other Ecosystem components. PELGAS therefore further developed the second objective of monitoring and studying the dynamic and diverse Biscay Pelagic Ecosystem in springtime. The PELGAS survey model has allowed for the establishment of a long-term time-series of spatially-explicit data of the Bay of Biscay Pelagic Ecosystem since the year 2000. Main sampled components of the targeted Ecosystem are: hydrology, phytoplankton, mesozooplankton, fish and megafauna. The survey now provides two main Ecosystem products: standard raster maps of Ecosystem parameters, and a time series dataset of indicators of the Bay of Biscay Pelagic Ecosystem state. They are used to inform fish stock and Ecosystem-based management, and support Ecosystem research. The present paper introduces the PELGAS survey, as a practical example of an integrated, vessel-based, Ecosystem survey. The evolution of the PELGAS scientific team and sampling protocols are presented and analysed, to outline factors crucial to the success of the survey. Data and results derived from PELGAS are reviewed, to exemplify scientific questions that can be tackled by integrated Ecosystem survey data. Advantages and challenges of the survey are discussed and put into the context of marine Ecosystem surveys in the European Marine Strategy Framework Directive and the Common Fisheries Policy.
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Pelagic fish stock assessment by acoustic methods at ifremer
EPIC3Nantes Centre de Nantes Département Écologie et Modèles pour l’Halieutique, 2010Co-Authors: Mathieu Doray, Jacques Masse, Pierre PetitgasAbstract:The main objective of Ifremer's Pelagic sea surveys (Pelgas in the Bay of Biscay and Pelmed in the Gulf of Lion) is to assess the biomass of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) populations, based on fisheries acoustic data. Complementary data on the whole Pelagic Ecosystem (hydrology, plankton, fish eggs and larvae, other fish species, seabirds and marine mammals) are also collected during the cruises. This document describes the procedures used to derive stock abundance estimates from acoustic and fishing data collected during sea cruises, the Pelgas sea survey being used as an example.