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Fernandez C.,Spanish Institute of Oceanography | Cervino S.,Spanish Institute of Oceanography | Perez N.,Spanish Institute of Oceanography | Jardim E.,IPIMAR
ICES Journal of Marine Science | Year: 2010

A Bayesian age-structured stock assessment model is developed to take into account available information on discards and to handle gaps in the time-series of discard estimates. The model incorporates mortality attributable to discarding, and appropriate assumptions about how this mortality may change over time are made. The result is a stock assessment that accounts for information on discards while, at the same time, producing a complete time-series of discard estimates. The method is applied to the hake stock in ICES Divisions VIIIc and IXa, for which the available data indicate that some 60 of the individuals caught are discarded. The stock is fished by Spain and Portugal, and for each country, there are discard estimates for recent years only. Moreover, the years for which Portuguese estimates are available are only a subset of those with Spanish estimates. Two runs of the model are performed; one assuming zero discards and another incorporating discards. When discards are incorporated, estimated recruitment and fishing mortality for young (discarded) ages increase, resulting in lower values of the biological reference points Fmax and F0.1 and, generally, more optimistic future stock trajectories under F-reduction scenarios. © 2010 United States Government, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southwest Fisheries Science Center. Source

Bundy A.,Bedford Institute of Oceanography | Shannon L.J.,University of Cape Town | Rochet M.-J.,French Research Institute for Exploitation of the Sea | Neira S.,Center for Ecosystem Research in Patagonia | And 4 more authors.
ICES Journal of Marine Science | Year: 2010

Marine ecosystems have been exploited for a long time, growing increasingly vulnerable to collapse and irreversible change. How do we know when an ecosystem may be in danger? A measure of the status of individual stocks is only a partial gauge of its status, and does not include changes at the broader ecosystem level, to non-commercial species or to its structure or functioning. Six ecosystem indicators measuring trends over time were collated for 19 ecosystems, corresponding to four ecological attributes: resource potential, ecosystem structure and functioning, conservation of functional biodiversity, and ecosystem stability and resistance to perturbations. We explored the use of a decision-tree approach, a definition of initial ecosystem state (impacted or non-impacted), and the trends in the ecosystem indicators to classify the ecosystems into improving, stationary, and deteriorating. Ecosystem experts classified all ecosystems as impacted at the time of their initial state. Of these, 15 were diagnosed as "ugly", because they had deteriorated from an already impacted state. Several also exhibited specific combinations of trends indicating "fishing down the foodweb", reduction in size structure, reduction in diversity and stability, and changed productivity. The classification provides an initial evaluation for scientists, resource managers, stakeholders, and the general public of the concerning status of ecosystems globally. © 2010 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved. Source

Perez S.,University of Santiago de Compostela | Vale C.,University of Santiago de Compostela | Alonso E.,University of Santiago de Compostela | Alfonso C.,University of Santiago de Compostela | And 7 more authors.
Chemical Research in Toxicology | Year: 2011

Ciguatera is a global disease caused by the consumption of certain warm-water fish (ciguateric fish) that have accumulated orally effective levels of sodium channel activator toxins (ciguatoxins) through the marine food chain. The effect of ciguatoxin standards and contaminated ciguatoxin samples was evaluated by electrophysiological recordings in cultured cerebellar neurons. The toxins affected both voltage-gated sodium (Nav) and potassium channels (Kv) although with different potencies. CTX 3C was the most active toxin blocking the peak inward sodium currents, followed by P-CTX 1B and 51-OH CTX 3C. In contrast, P-CTX 1B was more effective in blocking potassium currents. The analysis of six different samples of contaminated fish, in which a ciguatoxin analogue of mass 1040.6, not identical with the standard 51-OH CTX 3C, was the most prevalent compound, indicated an additive effect of the different ciguatoxins present in the samples. The results presented here constitute the first comparison of the potencies of three different purified ciguatoxins on sodium and potassium channels in the same neuronal preparation and indicate that electrophysiological recordings from cultured cerebellar neurons may provide a valuable tool to detect and quantify ciguatoxins in the very low nanomolar range. © 2011 American Chemical Society. Source

In statistical analysis of failure data of brittle materials, the use of maximum likelihood estimators shows many advantages compared to other methods. The applicability and the robustness of the maximum likelihood method to analyze and to distinguish the data in several mixtures of two Weibull populations is demonstrated in this work. Estimations of percentage of data belonging to each of the populations, as well as Weibull parameters of the populations, are relatively simple to be conducted using adequate software. © (2010) Trans Tech Publications. Source

Lorance P.,French Research Institute for Exploitation of the Sea | Agnarsson S.,University of Iceland | Damalas D.,Hellenic Center for Marine Research | Des Clers S.,University College London | And 3 more authors.
ICES Journal of Marine Science | Year: 2011

Stakeholder knowledge was collected through questionnaires and cognitive maps and used to summarize biological, environmental, technical, management, and socio-economic factors for several deep-water fisheries, identifying regional management issues and solutions. The questionnaires and cognitive maps revealed different technical, environmental, and management concerns in these fisheries. Dissatisfaction with management was more at an implementation than a conceptual level, because the existing management measures were mostly considered fit for purpose. Further, catch-and-effort data provided by the fishing industry were used to calculate standardized landings per unit effort. The results suggested different trends over time for three deep-water stocks exploited by the same fleet. The examples demonstrate how stakeholder involvement and use of qualitative knowledge and quantitative data might improve the management process and stock assessments when data are limited. © 2011 International Council for the Exploration of the Sea. Source

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