Sabiia Seb
PortuguêsEspañolEnglish
Embrapa
        Busca avançada

Botão Atualizar


Botão Atualizar

Ordenar por: RelevânciaAutorTítuloAnoImprime registros no formato resumido
Registros recuperados: 9
Primeira ... 1 ... Última
Imagem não selecionada

Imprime registro no formato completo
A Geostatistical Definition of Hotspots for Fish Spatial Distributions ArchiMer
Petitgas, Pierre; Woillez, Mathieu; Doray, Mathieu; Rivoirard, Jacques.
Research surveys at sea are undertaken yearly to monitor the distribution and abundance of fish stocks. In the survey data, a small number of high fish concentration values are often encountered, which denote hotspots of interest. But statistically, they are responsible for important uncertainty in the estimation. Thus understanding their spatial predictability given their surroundings is expected to reduce such uncertainty. Indicator variograms and cross-variograms allow to understand the spatial relationship between values above a cutoff and the rest of the distribution under that cutoff. Using these tools, a “top” cutoff can be evidenced above which values are spatially uncorrelated with their lower surroundings. Spatially, the geometric set...
Tipo: Text Palavras-chave: Hotspots; Indicators; Non-linear geostatistics; Multivariate geostatistics; Anchovy; Biscay.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00273/38380/36734.pdf
Imagem não selecionada

Imprime registro no formato completo
Evaluating the uncertainty of abundance estimates from acoustic surveys using geostatistical simulations ArchiMer
Woillez, Mathieu; Rivoirard, Jacques; Fernandes, Paul G..
Geostatistical simulations, which can reproduce the spatial variability of a variable, are particularly helpful in estimating the uncertainty associated with the combination of different sources of variability. Acoustic surveys offer an example of such complex situations, where different data (e.g. acoustic backscatter, fish length, and fish age) must be combined to estimate abundance and its associated uncertainty. In this paper, the uncertainty of Scottish herring acoustic-survey estimates is investigated using these techniques. A specific multivariate, geostatistical model is used to describe the structural relationships, which includes highly skewed distributions of the acoustic-backscatter data and incorporates relationships between depth, mean...
Tipo: Text Palavras-chave: Scottish herring; Geostatistics; Conditional simulations; Acoustic survey.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6760.pdf
Imagem não selecionada

Imprime registro no formato completo
From forager tracks to prey distributions: an application to tuna vessel monitoring systems (VMS) ArchiMer
Walker, Emily; Rivoirard, Jacques; Gaspar, Philippe; Bez, Nicolas.
In the open ocean, movements of migratory fish populations are typically surveyed using tagging methods that are subject to low sample sizes for archive tags, except for a few notable examples, and poor temporal resolution for conventional tags. Alternatively, one can infer patterns of movement of migratory fish by tracking movements of their predators, i.e., fishing vessels, whose navigational systems (e.g., GPS) provide accurate and frequent VMS (vessel monitoring system) records of movement in pursuit of prey. In this paper, we develop a state-space model that infers the foraging activities of fishing vessels from their tracks. Second, we link foraging activities to probabilities of tuna presence. Finally, using multivariate geostatistical interpolation...
Tipo: Text Palavras-chave: GPS; Multivariate geostatistics; Presence index; Spatiotemporal distribution; Trajectometry; Tropical tuna; Vessel monitoring system (VMS).
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00610/72249/71048.pdf
Imagem não selecionada

Imprime registro no formato completo
Indicator-Based Geostatistical Models For Mapping Fish Survey Data ArchiMer
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
Imagem não selecionada

Imprime registro no formato completo
Indices for capturing spatial patterns and their evolution in time, with application to European hake (Merluccius merluccius) in the Bay of Biscay ArchiMer
Woillez, M; Poulard, Jean-charles; Rivoirard, Jacques; Petitgas, Pierre; Bez, Nicolas.
A series of candidate statistical indices is used in an attempt to capture spatial patterns of fish populations from research survey data. To handle diffuse population limits, indices are designed not to depend on arbitrary delineation of the domain. They characterize the location (centre of gravity and spatial patches), the occupation of space (inertia, isotropy, positive area, spreading area, and equivalent area), statistical dispersion (Gini index and coefficient of variation of strictly positive densities), and microstructure. Collocation between different ages and years is summarized by a global index of collocation. Indices are estimated for hake from a bottom-trawl data series in the Bay of Biscay in autumn of 1987-2004. The study provides a...
Tipo: Text Palavras-chave: Spatial indices; European hake; Bay of Biscay.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2671.pdf
Imagem não selecionada

Imprime registro no formato completo
Notes on survey-based spatial indicators for monitoring fish populations ArchiMer
Woillez, Mathieu; Rivoirard, Jacques; Petitgas, Pierre.
This paper presents the spatial indicators used in the European project FISBOAT. These are statistics intended to capture spatial patterns of fish populations, using fish density data collected during scientific surveys. To handle diffuse population limits, indicators are designed not to depend on arbitrary delineation of the domain. They characterize the location (centre of gravity and spatial patches), occupation of space (inertia, isotropy, positive area, spreading area and equivalent area) and microstructure. Collocation between different populations is summarized by a global index of collocation. These spatial indicators have the potential to be used in a monitoring system to detect changes in spatial distribution. They could be helpful for relating...
Tipo: Text Palavras-chave: Fish populations; Spatial patterns; Monitoring; Spatial indicators.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6687.pdf
Imagem não selecionada

Imprime registro no formato completo
Relationships between population spatial occupation and population dynamics ArchiMer
Woillez, Mathieu; Petitgas, Pierre; Rivoirard, Jacques; Fernandes, Paul; Hoftstede, Remment Ter; Korsbrekke, Knut; Orlowski, Andrzej; Spedicato, Maria-teresa; Politou, Chrissi-yianna.
Population dynamics is commonly described non-spatially using parameters of population demography and vital traits. Population spatial organisation is therefore considered implicit and its importance in the population dynamics ignored. The present study evidences on a variety of stocks correlation between population spatial distribution indices, population abundance, recruitment and mortality. Series of research fisheries monitoring surveys were considered for a range of different stocks (cod, herring, anchovy, hake, mullet) in different regions of the North East Atlantic and Mediterranean (North Sea, Barents Sea, Baltic Sea, Bay of Biscay, Tyrrhenian Sea, Ionian Sea and Aegean Sea). For each population, each age and each year, 9 spatial indices were...
Tipo: Text Palavras-chave: Spatial indices population dynamics; Meta-analysis..
Ano: 2006 URL: http://archimer.ifremer.fr/doc/00133/24376/22388.pdf
Imagem não selecionada

Imprime registro no formato completo
Towards an ecosystem approach to fisheries management (EAFM) when trawl surveys provide the main source of information ArchiMer
Cotter, John; Petitgas, Pierre; Abella, Alvaro; Apostolaki, Panayiota; Mesnil, Benoit; Politou, Chrissi-yianna; Rivoirard, Jacques; Rochet, Marie-joelle; Spedicato, Maria Teresa; Trenkel, Verena; Woillez, Mathieu.
Ideas and considerations are put forward for managing fisheries and marine populations using primarily trawl surveys to supply biological and spatial indicators of the state of stocks, and to permit catch per unit effort (CPUE)-based assessments. Trawl surveys seldom allow absolute estimates of fish population sizes but, if appropriately located, timed, and designed, can provide a broad range of information about catchable fish species and the ecosystem that supports them. This information may be more conducive to sustainable management of fisheries than the traditional focus on the abundances of selected stocks. The paper first briefly proposes how survey-based methods might supplement existing fishery-dependent stock assessments, as would be necessary...
Tipo: Text Palavras-chave: Fishing effort indicator; Fisheries independent assessment; Survey based stock assessment; Spatial indicator; State indicator; Trawl survey; Fisheries management.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6691.pdf
Imagem não selecionada

Imprime registro no formato completo
Using min/max autocorrelation factors of survey-based indicators to follow the evolution of fish stocks in time ArchiMer
Woillez, Mathieu; Rivoirard, Jacques; Petitgas, Pierre.
Fisheries research monitoring surveys provide an ensemble of measurements on fish stocks and their environment. Because the interannual variability in such survey-based indicators is high and because diagnostics on fish stocks cannot be based on noise, our concern is to make use of what is continuous in time to obtain a reliable diagnostic. In this paper, we show how min/max autocorrelation factors (MAFs) can be useful for assessing the status of a fish stock. Indeed, MAFs will allow us to (i) summarize the multivariate indicator signals into orthogonal factors that are continuous in time, (ii) select those indicators that carry the major signal in time, and (iii) forecast stock status by modelling the time continuity of the MAFs. These different potential...
Tipo: Text Palavras-chave: Fish stock diagnostics; Survey based indicators; Time correlation; Min/max autocorrelation factors.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6759.pdf
Registros recuperados: 9
Primeira ... 1 ... Última
 

Empresa Brasileira de Pesquisa Agropecuária - Embrapa
Todos os direitos reservados, conforme Lei n° 9.610
Política de Privacidade
Área restrita

Embrapa
Parque Estação Biológica - PqEB s/n°
Brasília, DF - Brasil - CEP 70770-901
Fone: (61) 3448-4433 - Fax: (61) 3448-4890 / 3448-4891 SAC: https://www.embrapa.br/fale-conosco

Valid HTML 4.01 Transitional