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The relative importance of environmental stochasticity, interspecific interactions, and observation error: Insights from sardine and anchovy landings ArchiMer
Hosack, Geoffrey R.; Trenkel, Verena; Dambacher, Jeffrey M..
Long-term time series of sardine and anchovy landings often suggest negative dependence between these species, and an array of mechanisms have been proposed as explanations. We reduce these propositions to four basic hypotheses of (1) independence, (2) correlated process noise, (3) interspecific interactions, and (4) correlated observational error. We use a Bayesian approach to develop priors for parsimonious state space models with both process noise and observation error that represent each of these hypotheses, and apply this approach to five long-term time series of landings collected from the Pacific and Atlantic Oceans. Model comparison criteria suggest that the hypothesis of correlated process noise has the broadest support, where the temporal...
Tipo: Text Palavras-chave: Adaptive Metropolis; Bayes factors; DIC; Gompertz model; Hyperstability; Kalman filter; Model comparison; Reactivity; Small pelagic fishes; Stability.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00159/27072/26066.pdf
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Effects of Ignoring Survey Design Information for Data Reuse ArchiMer
Foster, Scott D.; Vanhatalo, Jarno; Trenkel, Verena; Schulz, Torsti; Lawrence, Emma; Przeslawski, Rachel; Hosack, Geoffrey R..
Data are currently being used, and reused, in ecological research at an unprecedented rate. To ensure appropriate reuse however, we need to ask the question: “Are aggregated databases currently providing the right information to enable effective and unbiased reuse?” We investigate this question, with a focus on designs that purposefully favour the selection of sampling locations (upweighting the probability of selection of some locations). These designs are common and examples are those designs that have uneven inclusion probabilities or are stratified. We perform a simulation experiment by creating datasets with progressively more uneven inclusion probabilities, and examine the resulting estimates of the average number of individuals per unit area...
Tipo: Text Palavras-chave: Bias; Survey Design; Database; Population Density Estimate; Model; Horvitz‐Thompson; FAIR; Reuse; Data; Inclusion Probability.
Ano: 2021 URL: https://archimer.ifremer.fr/doc/00691/80339/83422.pdf
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Functional group based marine ecosystem assessment for the Bay of Biscay via elasticity analysis ArchiMer
Hosack, Geoffrey R.; Trenkel, Verena.
The transitory and long-term elasticities of the Bay of Biscay ecosystem to densityindependent and density-dependent influences were estimated within a state space model that accounted for both process and observation uncertainties. A functional group based model for the Bay of Biscay fish ecosystem was fit to time series obtained from scientific survey and commercial catch and effort data. The observation model parameters correspond to the unknown catchabilities and observation error variances that vary across the commercial fisheries and fishery-independent scientific surveys. The process model used a Gompertz form of density dependence, which is commonly used for the analysis of multivariate ecological time series, with unknown time-varying fishing...
Tipo: Text Palavras-chave: Compensatory dynamics; Cumulative impacts; Elasticity; Fox model; Gompertz model; Predictive cross-validation.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00510/62119/66311.pdf
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