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| Registros recuperados: 99 | |
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| Trenkel, Verena; Mazauric, Valerie; Berger, Laurent. |
| Recently, Simrad in collaboration with Ifremer developed a calibrated, multibeam, vertical echosounder (ME70) for fisheries research. We describe its capabilities and technical limitations. The ME70 has up to 45 beams with distinct frequencies in the range 70120 kHz, spanning at most 150 degrees. All beams are stabilized in vessel roll and pitch. It has reduced side-lobe levels, up to -70 dB (two-way) instead of the -2S dB (one-way) of conventional systems. We outline research areas for which the ME70 might provide new types of information and hence lead to novel insights. We illustrate the potential contributions with datasets collected in the English Channel and on the continental-shelf break of the Bay of Biscay. Finally, future research and... |
| Tipo: Text |
Palavras-chave: Three dimensional; Behaviour; Acoustics; Abundance. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4117.pdf |
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| Trenkel, Verena. |
| A simple two-stage biomass random effects population dynamics model is presented for carrying out fish stock assessments based on survey indices using no commercial catch information. Recruitment and biomass growth are modelled as random effects, reducing the number of model parameters while maintaining model flexibility. No assumptions regarding natural mortality rates are required. The performance of the method was evaluated using simulated data with emphasis on identifying parameter redundancy, which showed that the variance of the biomass growth random effect might only be estimable if large (> 0.2). The full and two nested models were fitted to European anchovy (Engraulis encrasicolus) in the Bay of Biscay using two survey series. The best-fitting... |
| Tipo: Text |
Palavras-chave: Survey based assessment; Population state; Random effects. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4565.pdf |
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| Gimenez, Olivier; Buckland, Stephen T.; Morgan, Byron J. T.; Bez, Nicolas; Bertrand, Sophie; Choquet, Remi; Dray, Stephane; Etienne, Marie-pierre; Fewster, Rachel; Gosselin, Frederic; Merigot, Bastien; Monestiez, Pascal; Morales, Juan M.; Mortier, Frederic; Munoz, Francois; Ovaskainen, Otso; Pavoine, Sandrine; Pradel, Roger; Schurr, Frank M.; Thomas, Len; Thuiller, Wilfried; Trenkel, Verena; De Valpine, Perry; Rexstad, Eric. |
| The desire to predict the consequences of global environmental change has been the driver towards more realistic models embracing the variability and uncertainties inherent in ecology. Statistical ecology has gelled over the past decade as a discipline that moves away from describing patterns towards modelling the ecological processes that generate these patterns. Following the fourth International Statistical Ecology Conference (1–4 July 2014) in Montpellier, France, we analyse current trends in statistical ecology. Important advances in the analysis of individual movement, and in the modelling of population dynamics and species distributions, are made possible by the increasing use of hierarchical and hidden process models. Exciting research perspectives... |
| Tipo: Text |
Palavras-chave: Citizen science; Hidden Markov model; Hierarchical model; Movement ecology; Software package; Spatially explicit capture-recapture; Species distribution modelling; State-space model. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00249/36026/35298.pdf |
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| Trenkel, Verena; Rochet, Marie-joelle; Sari, Tewfik. |
| There exists an urgent need in fisheries science for simple models for assessing the impact of fishing on the dynamics of fish communities. We present a new class of predator prey models that describe the relationship between predators and their prey by piecewise-linear differential equations. Interactions are governed by threshold values for population abundances. The simplest model has four distinct cases with different asymptotic stable states. The model allows for fishing mortality on both predator and prey. If fishing mortality on either the predator, the prey or both are varied, the system might move to new stable states. The threshold values act as reference points for fishing exploitation, as they indicate a structural change in the predator-prey... |
| Tipo: Text |
Palavras-chave: Predator-prey model; Reference points; Differential equations. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/00453/56511/58207.pdf |
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| Trenkel, Verena; Ressler, Patrick H.; Jech, Mike; Giannoulaki, Marianna; Taylor, Chris. |
| Ecosystem-based management (EBM) requires more extensive information than single-species management. Active underwater acoustic methods provide a means of collecting a wealth of ecosystem information with high space-time resolution. Worldwide fisheries institutes and agencies are carrying out regular acoustic surveys covering many marine shelf ecosystems, but these data are underutilized. In addition, more and more acoustic data collected by vessels of opportunity are becoming available. To encourage their use for EBM, we provide a brief introduction to acoustic and complementary data collection methods in the water column, and review current and potential contributions to monitoring population abundance and biomass, spatial distributions, and... |
| Tipo: Text |
Palavras-chave: Active acoustics; Indicators; Ecosystem-based management. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00073/18445/15972.pdf |
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| Merino, Gorka; Barange, Manuel; Fernandes, Jose A.; Mullon, Christian; Cheung, William; Trenkel, Verena; Lam, Vicky. |
| It is accepted that world’s fisheries are not generally exploited at their biological or their economic optimum. Most fisheries assessments focus on the biological capacity of fish stocks to respond to harvesting and few have attempted to estimate the economic efficiency at which ecosystems are exploited. The latter is important as fisheries contribute considerably to the economic development of many coastal communities. Here we estimate the overall potential economic rent for the fishing industry in the North Atlantic to be B€ 12.85, compared to current estimated profits of B€ 0.63. The difference between the potential and the net profits obtained from North Atlantic fisheries is therefore B€ 12.22. In order to increase the profits of North Atlantic... |
| Tipo: Text |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00188/29973/28426.pdf |
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| Trenkel, Verena; Skaug, Hans. |
| We propose a random effects model for disentangling population abundance and capture efficiency effects on bottom-trawl catches. The spatial distribution of individual fish is assumed random leading to a Poisson distribution for the number of individuals in the trawl path (no schooling). Capture efficiency, i.e. the proportion of individuals in the trawl path being retained by the gear, is modelled as a random variable. We propose model extensions that include the effects of body size on haul efficiency. We applied the models to several species from the Celtic Sea groundfish community based on small-scale repetitive hauls. The resulting abundance estimates allowed us to study population abundance ratios; the estimated capture efficiencies were comparable... |
| Tipo: Text |
Palavras-chave: Trawl survey; Poisson distribution; Celtic Sea; Catchability; Abundance. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-828.pdf |
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| Berger, Laurent; Poncelet, Cyrille; Trenkel, Verena. |
| Fish schools can be insonified simultaneously with multifrequency echosounders (e.g. Simrad EK60s) and a multibeam echosounder (e.g. Simrad ME70). This paper presents a method for combining these data to improve estimates of the relative frequency response r(f) of fish schools. Values of r(f) are now commonly used to classify echoes in fishery surveys. The data from the roll- and pitch-stabilized, high-resolution ME70 are used to correct beam-width effects in the multifrequency EK60 data. First, knowing the exact position and orientation of the transducers and the position of the vessel, the echoes are placed into a common geographic coordinate system. Then, the EK60 data are rejected if they do not include a significant percentage of the fish school... |
| Tipo: Text |
Palavras-chave: Species identification; Scomber scombrus; Sardina pilchardus; Pelagic fish; Acoustics. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6590.pdf |
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| Rochet, Marie-joelle; Trenkel, Verena; Carpentier, Andre; Coppin, Franck; Gil De Sola, Luis; Leaute, Jean-pierre; Mahe, Jean-claude; Maiorano, Porzia; Mannini, Alessandro; Murenu, Matteo; Piet, Gerjan; Politou, Chrissi-yianna; Reale, Bruno; Spedicato, Maria-teresa; Tserpes, George; Bertrand, Jacques. |
| P>1. The development of ecosystem approaches to environmental management implies the need to account for multiple pressures on ecosystems. Trends in multiple metrics that respond differently to changes in major environmental pressures need to be combined to evaluate the impacts of fishing and environmental changes on fish communities. 2. An exploited fish community is viewed as a three-level food chain in which the two upper levels, or functional groups, are targeted by fishing fleets, while the lowest level is subject to environmental variation. Qualitative modelling is used to predict changes at the two upper levels, that is, top-down vs. bottom-up perturbations. Abundance and length metrics are calculated from survey data for 14 Mediterranean and... |
| Tipo: Text |
Palavras-chave: Bottom-up control; Community metrics; Compensation; Ecosystem approach to fisheries; Ecosystem assessment; Functional groups; Groundfish community; Mediterranean; North Atlantic; Top-down control. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00008/11925/8637.pdf |
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| Lorance, Pascal; Agnarsson, Sveinn; Damalas, Dimitrios; Des Clers, Sophie; Figueiredo, Ivone; Gil, Juan; Trenkel, Verena. |
| 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... |
| Tipo: Text |
Palavras-chave: Closure; Control; Cpue; Regulation; SWOT; TAC; Technical measures. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00043/15420/13376.pdf |
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| Mahevas, Stephanie; Trenkel, Verena; Doray, Mathieu; Peyronnet, Arnaud. |
| Several factors affect trawl catchability: (i) gear and vessel technical characteristics, (ii) anthropogenic factors, and (iii) biological factors. The objectives of this study were to assess the relative contribution of each factor to variations in hake (Merluccius merluccius) landings by the French trawler fleet operating on the shelf of the northern Bay of Biscay (ICES Subdivision VIIIa). Using generalized linear models, the impact of technical and anthropogenic factors was evaluated using landings per unit effort (lpue) obtained from logbooks. Variations in hake lpue were explained primarily by anthropogenic factors. For studying the biological components of catchability, the results of a scientific trawl survey in July 2006 involving three similar... |
| Tipo: Text |
Palavras-chave: Accessibility; Beam trawl; Catchability; Fishing power; GLMM; Spatial distribution. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00021/13244/10287.pdf |
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| 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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| Vignet, Caroline; Trenkel, Verena; Vouillarmet, Annick; Bricca, Giampiero; Begout, Marie-laure; Cousin, Xavier. |
| Zebrafish were exposed through diet to two environmentally relevant polycyclic aromatic hydrocarbons (PAHs) mixtures of contrasted compositions, one of pyrolytic (PY) origin and one from light crude oil (LO). Monoamine concentrations were quantified in the brains of the fish after six month of exposure. A significant decrease in noradrenaline (NA) was observed in fish exposed to both mixtures, while a decrease in serotonin (5HT) and dopamine (DA) was observed only in LO-exposed fish. A decrease in metabolites of 5HT and DA was observed in fish exposed to both mixtures. Several behavioural disruptions were observed that depended on mixtures, and parallels were made with changes in monoamine concentrations. Indeed, we observed an increase in anxiety in fish... |
| Tipo: Text |
Palavras-chave: Monoamine; Polycyclic aromatic hydrocarbons; Behaviour; Anxiety; Swimming activity; Zebrafish. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00375/48578/48900.pdf |
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| Gascuel, D.; Bez, Nicolas; Forest, Andre; Guillotreau, P.; Laloe, F.; Lobry, Jeremy; Mahevas, Stephanie; Mesnil, Benoit; Rivot, Etienne; Rochette, S.; Trenkel, Verena. |
| We, members of the Association Francaise d'Halieumetrie, share the conviction that European fisheries have a future. It is time to get off the wrong track. Radical change is required to embark on the path of sustainable development and truly implement the ecosystem approach to fisheries. Today, high fishing pressure is deployed to catch a rare resource, which in return is responsible for the rarity. We must reverse the situation: an abundant resource that affords high catches applying moderate fishing pressure. All management tools and especially all actors must be mobilized. The transition is not simple, and European solidarity must accompany the changes. It is well worth the effort. By reducing fishing pressure, it will be possible in the medium term to... |
| Tipo: Text |
Palavras-chave: Access regulation; Ecosystem approach to fisheries; European Common Fishery Policy; ITQ; MPA; MSY; Management plan; Overcapacity; Subsidies. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00035/14598/11947.pdf |
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| Moriarty, M.; Sell, A. F.; Trenkel, Verena; Lynam, C. P.; Burns, F.; Clarke, E. D.; Greenstreet, S. P. R.; Mcgonigle, C.. |
| An experiment during a fisheries independent survey in the North Sea was conducted to test whether sampling effort could be reduced without a significant loss in data precision. To examine potential effects of reducing tow duration from the standard 30 min to a proposed 15 min estimates of species encounter rates, species richness, and estimates of abundance, biomass, and body size were analysed. Results show species richness estimates are lower in the short tow category. While biomass and abundance at length and body size are significantly affected by the change in tow duration, estimates of Large Fish Indicator, the Typical length and Mean-max length are not significantly affected by the regime change. The results presented here suggest that a reduction... |
| Tipo: Text |
Palavras-chave: Abundance; Biomass; Body size; Fisheries independent survey; IBTS; International Bottom Trawl Survey; Linear mixed model; North Sea; Species diversity. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00439/55028/60477.pdf |
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| Trenkel, Verena; Marandel, Florianne; Lorance, Pascal. |
| Sustainable fisheries management requires the evaluation of the status of exploited populations and communities. Certain bycatch species such as rays are managed together which has led to overexploitation and conservations concerns for the most vulnerable ones. Traditional fisheries stock evaluation methods need species-specific input data while for ray species-specific landings have become available only recently in Europe. To overcome data limitations caused by grouped landings we developed a Bayesian multispecies biomass production model. In addition to the grouped landings the input data are shorter time series with species-specific information (landings and scientific biomass indices). Life history traits are used to define informative priors for... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00470/58214/60718.pdf |
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| Bertrand, Jacques; Cochard, Marie-laure; Coppin, Franck; Le Pape, Olivier; Mahe, Jean-claude; Morin, Jocelyne; Poulard, Jean-charles; Rochet, Marie-joelle; Schlaich, Ivan; Souplet, Arnauld; Trenkel, Verena; Verin, Yves. |
| The scientist community, the fishing organisations and all involved parties show a growing interest in an integrated project management of the sea space exploited by fishing communities. A key to reach such a target is to make available reliable and precise scientist data on the different components of the fishing systems. For about twenty years, and in its mission to support the development of an integrated management for a sustainable use of marine resources, Ifremer has been organising monitoring campaigns of fishery resources along the shores of France. These campaigns aim at providing abundance indicator on species of interest. They consequently provide an essential knowledge base to characterize and trace the status of exploited fish and... |
| Tipo: Text |
Palavras-chave: Ecosystem; Indicating; Oceanographical campaign; Scientific research; Fishing halieutic; Fishing; English Channel; Bay of Biscay; France; Invertebrate; Pisces; Ecosystème; Indicateur; Campagne océanographique; Recherche scientifique; Pêche halieutique; Pêche; Mer du nord; Golfe de gascogne; Manche; France; Invertebrate; Pisces. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/rapport-1091.pdf |
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| Pinnegar, J; Trenkel, Verena; Tidd, A; Dawson, W; Du Buit, M. |
| Feeding preferences of Celtic Sea fishes were investigated using a database of stomach content records, collected between 1977 and 1994. The diet of cod Gadus morhua, hake Merluccius merluccius, megrim Lepidorhombus whiffiagonis, whiting Merlangius merlangus and saithe Pollachius virens changed markedly as the animals grew larger, and although large predators generally chose larger bodied prey, the variability of prey sizes consumed also increased. Large predators continued to select small, low value, benthic prey (e.g. Callionymus spp. and Trisopterus spp.) which were easier to catch, rather than larger, more energy lucrative pelagic prey (e.g. mackerel Scomber scombrus), even though these pelagic prey-fishes were nearly always available and were often... |
| Tipo: Text |
Palavras-chave: Stomach contents; Preference; Diet; Celtic Sea; Availability. |
| Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/2003/publication-607.pdf |
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| Registros recuperados: 99 | |
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