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| Registros recuperados: 105 | |
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| Petitgas, Pierre. |
| Protocol established during the 2005 and 2006 Pelgas campaigns, for anchovy eggs in the Bay of Biscay. The density column used is Coombs' (1981). Egg density varies according to surface hydrological conditions (Petitgas et al., 2006), which necessitates a routine measurement of egg density according to a set protocol. |
| Tipo: Text |
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| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/rapport-6434.pdf |
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| Doray, Mathieu; Petitgas, Pierre; Nelson, Laetitia; Mahevas, Stephanie; Josse, E; Reynal, Lionel. |
| Fish-aggregating devices (FADs) are increasingly used worldwide to enhance tuna catches. Meanwhile, ecosystem-based management of this fishery is constrained by a paucity of information regarding the interaction of FAD-associated tuna aggregations with their local environment. This paper reports the results of a nine-month study around a FAD moored near Martinique Island, aimed at assessing the effects of the local environment on the variability of monthly estimates of proximate tuna biomass. Dual-frequency, active acoustics provided highresolution quantitative data on the pelagic community around the FAD, from fish to micronekton forage. Geostatistics were used to compute biomass estimates of the tuna aggregation comprising most of the FADassociated fish... |
| Tipo: Text |
Palavras-chave: Lesser Antilles; Tuna; Environment; Geostatistics; Biomass estimation; Fish aggregating device. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6162.pdf |
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| Bellier, Edwige; Planque, Benjamin; Petitgas, Pierre. |
| The spatial extent of small pelagic fish spawning habitat is influenced by environmental factors and by the state of the adult population. In return, the configuration of spawning habitat affects recruitment and therefore the future structure of the adult population. Interannual changes in spatial patterns of spawning reflect variations in adult population structures and their environment. The present study describes the historical changes in the spatial distribution of spawning of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Bay of Biscay during two periods: 1967-72 and 2000-2004. Using data from egg surveys conducted in spring, the spatial distributions of anchovy and sardine eggs are characterized by means of geostatistics.... |
| Tipo: Text |
Palavras-chave: Spawning habitat; Spatial patterns; Sardine; Long term changes; Bay of Biscay; Anchovy. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2179.pdf |
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| Koutsikopoulos, Constantin; Petitgas, Pierre. |
| It is often necessary to sub-sample plankton samples even if the precision of the estimation is thereby decreased. A methodological optimization is looked for. The variance depends on the procedure of construction of the aliquot (strategy) and the number of individuals counted (effort). The sub-sampling effort is allocated in a general context of repartition of the total effort between sampling and sub-sampling. This effort depends on the time consumed by the sub-sampling procedure, the volume of the aliquot and the number of individuals counted. For the same effort, a systematic procedure for the construction of sub-samples is more precise than a random one because it travels through the entire sample and is thus less dependent on the spatial distribution... |
| Tipo: Text |
Palavras-chave: Plancton; Sous-échantillonnage; Effort; Précision; Plankton; Sub-sampling; Effort; Precision. |
| Ano: 1990 |
URL: http://archimer.ifremer.fr/doc/00131/24259/22252.pdf |
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| Huret, Martin; Petitgas, Pierre; Bourriau, Paul; Grellier, Patrick. |
| The objective of the study is a better understanding of recruitment variability in anchovy population. An Individual Based Model (IBM) is being developed for the full life cycle of anchovy. The early life stages are presented on this poster. The model is tested in a 1D-vertical framework for validation of the vertical distribution of modelled eggs and larvae against in-situ data. The dynamic Energy Budget (DEB) theory is the biological baseline for individual growth. We test its ability to simulate the observed growth curves between years with contrasted temperatures. |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00054/16508/14022.pdf |
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| Doray, Mathieu; Petitgas, Pierre; Josse, E. |
| Universal kriging was used to model the spatio-temporal variability in the acoustic density of tuna aggregations recorded during star echosounding surveys around moored fish aggregating devices (FADs) in Martinique (Lesser Antilles). The large-scale deterministic drift in the tuna spatial distribution was modeled using an advection-diffusion equation applied to animal grouping. Residuals from the drift were modeled as a random component with small-scale spatial correlation. An estimation variance formula was derived from this deterministic-statistical mixed model to assess the mean precision of density estimates of daytime tuna aggregation. The mean relative error obtained with our star design for daytime surveys was 24%. The methodology was applied to... |
| Tipo: Text |
Palavras-chave: Acoustic survey precision; Advection diffusion model; Moored fish aggregating devices; Tuna; Geostatistics. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4559.pdf |
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| Petitgas, Pierre; Woillez, Mathieu; Doray, Mathieu; Rivoirard, Jacques. |
| Marine research survey data on fish stocks often show a small proportion of very high-density values, as for many environmental data. This makes the estimation of second-order statistics, such as the variance and the variogram, non-robust. The high fish density values are generated by fish aggregative behaviour, which may vary greatly at small scale in time and space. The high values are thus imprecisely known, both in their spatial occurrence and order of magnitude. To map such data, three indicator-based geostatistical methods were considered, the top-cut model, min–max autocorrelation factors (MAF) of indicators, and multiple indicator kriging. In the top-cut and MAF approaches, the variable is decomposed into components and the most continuous ones... |
| Tipo: Text |
Palavras-chave: Top-cut; MAF; Indicators; Co-kriging; Skewed distribution; Anchovy; Bay of Biscay; Fisheries survey data; Aggregation. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00429/54021/55339.pdf |
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| Huret, Martin; Petitgas, Pierre; Struski, Caroline. |
| Fish populations show complex life cycles with successive dependent life stages, the spatio-temporal patterns of distribution at one stage impacting distribution, growth and mortality during the next stage. Here we propose to assess the relative effect of spawning (timing, duration, fecundity and spatial distribution, resulting from adult environmental conditions over autumn and winter) and larval mortality on the resulting survival at the age of metamorphosis. We used a suite of models run sequentially : a coupled physical-biogeochemical model to provide the environmental forcing, a Dynamic Energy Budget (DEB) model for adult fish growth and reproduction (spawning timing, duration and fecundity), an Individual Based Model (IBM) for larval drift, growth... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00023/13451/10464.pdf |
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| Petitgas, Pierre; Magri Hoeltzener, Stephanie; Lazure, Pascal. |
| Modelling the vertical distribution of fish eggs is important when assessing fish stocks with egg production methods and for monitoring the reproductive potential of fish populations. Fish eggs are passive particles and their vertical distribution is determined by a few parameters such as egg density, egg diameter, wind- and tide-induced turbulence, and vertical hydrographic structure. A one-dimensional vertical biophysical, numerical model was developed which was adapted to the hydrography of shelf seas under the influence of tidal currents, wind-induced circulation, and river discharges. The biological part of the model parameterized the ascent velocity of the egg as a function of egg properties (diameter, density) and water properties (density,... |
| Tipo: Text |
Palavras-chave: Vertical distribution; Sprat; Sardine; Fish egg buoyancy; CUFES; Biophysical coupling; Anchovy. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-2277.pdf |
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| Doray, Mathieu; Berger, Laurent; Le Bouffant, Naig; Coail, Jean-yves; Vacherot, Jean-philippe; De La Bernardie, Xavier; Moriniere, Pierre; Lys, Elisabeth; Schwab, Romain; Petitgas, Pierre. |
| Measuring fish target strength (TS) in the wild is challenging because: (i) TS varies versus physical (orientation relative to the incident sound wave, size, and depth) and physiological fish attributes (maturity and condition), (ii) the target species and its aforementioned attributes are difficult to assess in near real time, and (iii) in the case of packed fish schools, accepted echoes may originate from multiple unresolved targets. We propose a method for controlled TS measurements of densely packed small pelagic fish during daytime, based on the joint use of a Remotely Operated Towed Vehicle, “EROC”, with a pelagic trawl fitted with a codend opening system, “ENROL”. EROC, equipped with a 70-kHz split-beam echosounder (Simrad EK60) and a low-light... |
| Tipo: Text |
Palavras-chave: Acoustics; Deformed cylinder model; Engraulis encrasicolus; Remotely operated vehicle; Target strength; Video. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00346/45693/45623.pdf |
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| Petitgas, Pierre; Alheit, Juergen; Peck, Myron A.; Raab, Kristina; Irigoien, Xabier; Huret, Martin; Van Der Kooij, Jeroen; Pohlmann, Thomas; Wagner, Carola; Zarraonaindia, Iratxe; Dickey-collas, Mark. |
| The abundance and spatial occupation of European anchovy Engraulis encrasicolus have increased in the North Sea since the mid-1990s. We use a cross-disciplinary approach combining genetics, transport modelling, survey time series analyses and physical oceanographic modelling to investigate 3 hypotheses on the reasons for this change. Evidence from connectivity studies suggests that the population of North Sea anchovy is separate from that in the Bay of Biscay. The recruitment pulses observed in survey data fit a life cycle which includes spawning in early summer and larval development in late summer. This also supports the concept of population expansion originating from local remnant population(s). In terms of growth physiology, suitable thermal windows... |
| Tipo: Text |
Palavras-chave: Climate variability; Small pelagic fish; Regime shift; Temperature; Anchovy; North Sea. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00060/17140/14638.pdf |
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| Doray, Mathieu; Petitgas, Pierre; Masse, Jacques. |
| Estimer la biomasse d'un stock de poissons par acoustique nécessite de combiner des données de nature diverse collectées le long du parcours d'échantillonnage (Woillez et al., 2009). Il s'agit essentiellement de combiner trois champs de données spatialisées : une carte de densités acoustiques attribuées aux poissons, une carte de proportions d'espèces et une carte de longueurs moyennes. |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00003/11447/7997.pdf |
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| Doray, Mathieu; Petitgas, Pierre; Romagnan, Jean-baptiste; Huret, Martin; Duhamel, Erwan; Dupuy, Christine; Spitz, Jérôme; Berger, Laurent; Dorémus, Ghislain; Bourriau, Paul; Grellier, Patrick; Massé, Jacques; Sanchez, Florence. |
| The initial objective of the PELGAS integrated survey was to assess the biomass of small pelagic fish in the Bay of Biscay in spring. Sampling has been extended to study the spatial structure and dynamics of the pelagic ecosystem in springtime. The PELGAS survey has produced since 2000 long-term time-series of spatially-explicit data and indices, describing the main pelagic ecosystem components: hydrology, phytoplankton, mesozooplankton, fish and megafauna. In addition to small pelagic fish biomass estimates used for fish stock assessment, the survey now delivers two types of ecosystem products: standard gridded maps of ecosystem parameters, and a time series dataset of indicators of the Bay of Biscay pelagic ecosystem state. The evolution of the PELGAS... |
| Tipo: Text |
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| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00457/56844/58693.pdf |
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| Huret, Martin; Petitgas, Pierre; Struski, Caroline; Leger, Fabien; Sourisseau, Marc; Lazure, Pascal. |
| Overexploitation and climate change are increasingly causing unanticipated changes in marine ecosystems, such as higher variability in fish recruitment and shifts in species distribution, pressing for developing fisheries oceanography. In the meantime, operational oceanography rapidly progresses and its products become easy to access to a large community, among them fisheries scientists. Multiyear oceanographic reanalyses (hindcasts) were identified has a priority product by the ICES WG on Operational Oceanographic Products for Fisheries and Environment (WGOOFE). We performed a 37 years hindcast (1972-2008) run with a coupled physical-biogeochemical model (ECO-MARS3D) over the Bay of Biscay, using realistic meteorological and run-off forcing. We first... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00023/13432/10442.pdf |
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| Politikos, Dimitrios; Huret, Martin; Petitgas, Pierre. |
| Modelling of fish movement behaviour within a heterogeneous marine environment is a challenging but also key issue for understanding the effect of environmental factors and climatic change on fish processes (growth, distribution, mortality, reproduction). Fish movement models have the capability to encompass the combined effect of environment and empirical knowledge of fish individuals as energy requirements, known preys and predators, swimming capacities into a unified framework. Following an Individual Based Model (IBM) approach, a fish movement model has been developed to simulate the active movement of adult anchovy in the Bay of Biscay (BoB) in response to the spatio-temporal variations of both biotic and abiotic factors, as well as its internal... |
| Tipo: Text |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00176/28709/27161.pdf |
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| Allain, Gwenhael; Petitgas, Pierre; Lazure, Pascal. |
| A growth and survival model of the early life stages was run along virtual drift trajectories tracked in a hydrodynamic model to simulate the annual recruitment process of anchovy (Engraulis encrasicolus) in the Bay of Biscay (NE Atlantic). These biophysical simulations concerning three different years were analysed in order to investigate the influence of environment and spawning dynamics on the survival of larvae and juveniles. The location of space-time survival windows suggested major environmental mechanisms involved in simulated recruitment variability at the different scales - retention of larvae and juveniles in favourable habitats over the shelf margins and turbulence effects. These small-scale and meso-scale mechanisms were related to the... |
| Tipo: Text |
Palavras-chave: Turbulence; Retention; Recruitment; Physical biological interactions; Larval survival; IBM; Biscay; Anchovy. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3423.pdf |
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| Registros recuperados: 105 | |
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