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| Registros recuperados: 99 | |
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| Daures, Fabienne; Trenkel, Verena; Guyader, Olivier. |
| Ten years after the start of the European Data Collection Framework the availability of cost indicators for assessing the economic status of fisheries or bio-economic modelling is still deficient. Moreover, economic time series are difficult to maintain due to fishermen weariness and sample coverage is often insufficient. To overcome these problems, the paper builds predictive models per operational cost category (fuel, landing, other variable, fixed, salary and total) for the French Bay of Biscay fleet. The cost models had good fit and stressed the key role of gear and vessel size (length mostly) for explaining fishing costs. They suggested that only a small list of variables was needed to predict costs (days-at-sea, total revenue, vessel age, length and... |
| Tipo: Text |
Palavras-chave: Socio-economic; Empirical cost model; Fisheries performance; Gear type; GAM; Ecosystem Approach to Fisheries. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00149/26039/24410.pdf |
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| Trenkel, Verena; Lorance, Pascal. |
| Kaup's arrowtooth eel Synaphobranchus kaupii is a small-bodied fish and an abundant inhabitant of the European continental slope. To estimate its local density video information using the remotely operated vehicle (ROV) Victor 6000 were collected at three locations in the Bay of Biscay slope. Two methods for estimating local densities were tested: strip transect counts and bait experiments. For bait experiments three behaviour types were observed in about equal proportions for individuals arriving near the seafloor: moving up the current towards the ROV, moving across the current and drifting with the current. Visible attraction towards the bait was the highest for individuals swimming against the current (80%) and about equally low for the other two types... |
| Tipo: Text |
Palavras-chave: Bayesian; Hierarchical model; Natural and reaction behaviour; Video; Deep-water. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00031/14198/11523.pdf |
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| Trenkel, Verena. |
| n this paper, I argue that we have at hand what is needed to provide scientific advice for ecosystem-based management of small pelagics and other species groups now. The ingredients for this advice are (i) large marine ecosystems as spatial management units; (ii) maintaining ecosystem productivity and exploiting at multispecies maximum yield as overarching management objectives; (iii) assessment of ecosystems by evaluating changes in primary productivity; (iv) an operational management procedure in which single-species catch proposals are adjusted to ecosystem productivity using a set of control rules. Inspection of historic landings for small pelagics and other small species in the Northeast Atlantic (ICES area) reveals that most likely fisheries... |
| Tipo: Text |
Palavras-chave: EBFM; Fisheries management; Fisheries yield; Primary production. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00416/52784/53851.pdf |
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| Trenkel, Verena; Rochet, Marie-joelle; Mesnil, Benoit. |
| Traditional advice for fisheries management, especially in the ICES world, focuses on short-term stock projections relative to reference points. Primarily, two numbers, spawning-stock biomass and fishing mortality rate, are considered in the advice, although a range of biological processes are included in the stock assessment models. We propose an alternative form of final advice that would not rely on stock predictions and only two numbers, but on a suite of indicators that are combined to provide stock assessment and management advice. For a single stock, the approach consists of monitoring a set of indicators of population state and fishing pressure. Stock reference status at some time in the past is assessed, based on these indicators and/or other... |
| Tipo: Text |
Palavras-chave: Scientific advice; Indicators; Fisheries management. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2619.pdf |
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| Lassalle, Geraldine; Pasqual, Jean-sebastien Nelva; Boet, Philippe; Rochet, Marie-joelle; Trenkel, Verena; Niquil, Nathalie. |
| To develop and implement ecosystem-based management, it is critical to monitor foodweb components or functional groups which are robust to uncertainty in ecosystem structure and functioning yet sensitive to changes. To select such functional groups for the Bay of Biscay continental shelf, both quantitative and qualitative foodweb models were developed. First, functional groups for which predictions of directions of change following an increase in primary productivity, prey or predators, or in fishing activities were identical across alternative qualitative model structures were identified. Second, the robustness to model type was assessed by comparing qualitative predictions with quantitative Ecopath model results. The demersal fish community was... |
| Tipo: Text |
Palavras-chave: Comparative studies; Ecosystem management; Foodweb; Loop analysis; Northeast Atlantic continental shelf. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00173/28427/26852.pdf |
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| Trenkel, Verena; Cotter, John. |
| Ecosystem assessments of fisheries based only on survey data will often have to use surveys that were designed historically for special purposes, e. g. for assessing abundances of two or three target species, or for tuning VPAs. An important question then is whether the previously collected data can provide informative time series of abundance indices and other state indicators for a wider range of target and non-target species. Some potential shortcomings of existing data series are treated in this paper leading to four questions which can guide the user to determine the suitability of an existing time series: did the survey cover the stock of each species adequately? Did survey catchability vary significantly between length or age classes? Did survey... |
| Tipo: Text |
Palavras-chave: Bias; Survey based methods; Indicators. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6900.pdf |
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| Blanchard, Julia L.; Coll, Marta; Trenkel, Verena; Vergnon, Remi; Yemane, Dawit; Jouffre, Didier; Link, Jason S.; Shin, Yunne-jai. |
| Time-series of ecological and exploitation indicators collected from 19 ecosystems were analysed to investigate whether there have been temporal trends in the status of fish communities. Using linear and non-linear statistical methods, trends are reported for six indicators (mean length of fish in the community, mean lifespan, proportion of predatory fish, total biomass of surveyed species, mean trophic level of landings, and inverse fishing pressure), and the redundancy of these indicators across ecosystems is evaluated. The expected direction of change for an ecosystem that is increasingly impacted by fishing is a decline in all indicators. A mixture of negative and positive directions of change is recorded, both within and among all ecosystems... |
| Tipo: Text |
Palavras-chave: Community; Ecological indicators; Ecosystem-based fisheries management; Ecosystem effects of fishing; Natural resource management. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00002/11373/8166.pdf |
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| Rochet, Marie-joelle; Prigent, M; Bertrand, Jacques; Carpentier, Andre; Coppin, Franck; Delpech, Jean-paul; Fontenelle, G; Foucher, Eric; Mahe, Kelig; Rostiaux, Emilie; Trenkel, Verena. |
| The results of a survey on fishers' perceptions of recent changes in the eastern English Channel ecosystem carried out in 2006 were compared with fishery and bottom-trawl survey data. A hypothesis-testing framework was used, testing the null hypothesis that fishers' statements were true, which permitted evaluation of both agreement and disagreement. Overall good agreement between fishers' statements and scientific data was found, and both sources suggested that the fish community in the Channel is undergoing large changes, among which are decreases in some commercially important species; in addition, a number of human pressures impact the ecosystem. Fishers had an accurate perception of changes and their time-frames, but not necessarily of their causes.... |
| Tipo: Text |
Palavras-chave: Stakeholder interview; Hypothesis testing; Fisher knowledge; Ecosystem approach to fisheries management; Eastern English Channel. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4474.pdf |
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| Trenkel, Verena. |
| In my work, which is summarised in this paper for obtaining accreditation to supervise research (the HDR), I addressed three areas: i) statistical methods of estimating the density of living resources, ii) mathematical models of population dynamics for estimating the abundance of marine populations and iii) methods for detecting temporal changes in the status of exploited populations. My work has focused on: i) Many studies of the observability of fish by trawling and by video and the development of stochastic models to better assess local fish densities. ii) Development of models without commercial catches, using Bayesian and frequentist approaches; the study of multi-specific relationships and the proposal for a threshold predator-prey model. iii)... |
| Tipo: Text |
Palavras-chave: Statistics; Abundance estimation; Stock assessment; Statistiques; Estimation d'abondance; Evaluation des stocks. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/rapport-1545.pdf |
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| Trenkel, Verena; Pinnegar, John; Rochet, Marie-joelle; Rackham, Brian. |
| Choice of sampling method and survey period can have an important impact on the perception of the structure and dynamics of an ecological community. For the Celtic Sea fish assemblage we compared data obtained by three different trawl surveys: an autumn groundfish survey with a GOV trawl, and a spring and an autumn groundfish survey, both carried out with a Portuguese high-headline trawl. Time-series of abundance estimates were not consistent among surveys for all species and were generally very noisy. An analysis of variance components showed that the sampling method contributed more to the variance in abundance estimates compared to survey period, interannual variability, or even sampling variance. Overall community assessments based on indicators such... |
| Tipo: Text |
Palavras-chave: Trawl; Survey; Species diversity; Size spectrum; Celtic Sea; Abundance. |
| Ano: 2004 |
URL: https://archimer.ifremer.fr/doc/2004/publication-899.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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| Trenkel, Verena; Berthele, Olivier; Lorance, Pascal; Bertrand, Jacques; Brind'Amour, Anik; Cochard, Marie-laure; Coppin, Franck; Leaute, Jean-pierre; Mahe, Jean-claude; Morin, Jocelyne; Rochet, Marie-joelle; Salaun, Michele; Souplet, Arnauld; Verin, Yves. |
| Depuis une vingtaine d'années, l'Ifremer organise des campagnes de pêche scientifique en mer du Nord, Manche, Atlantique et Méditerranée concernant les ressources pélagiques, démersales et benthiques. L'objectif prioritaire est de produire des indices d'abondance des principales espèces commerciales. Elles recueillent également des données sur les espèces capturées non commerciales. Les campagnes sont réalisées selon des plans d'échantillonnage standardisés. L'engin de pêche et son gréement, la position des stations, le tri des captures, les prélèvements biologiques suivent des protocoles fixés. Chaque zone étudiée est découpée en fonction de la profondeur, de la latitude ou d'autres critères. L'échantillonnage prévoit un nombre de traits de chalut... |
| Tipo: Text |
Palavras-chave: Populations; Halieutique; Bulletin; Méditerranée; Golfe de Gascogne; Manche; Mer du Nord; France; Pêche; Campagnes à la mer; Atlas; Survey; Mediterranean Sea; Bay of Biscay; English Channel; North Sea; France; Populations; Fishery science; Bulletin; Atlas. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/rapport-6976.pdf |
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| Trenkel, Verena; Pinnegar, J; Dawson, W; Du Buit, M; Tidd, A. |
| The spatial and temporal structure of predator-prey relationships in the Celtic Sea was investigated for 4 commercially important predator species (cod Gadus morhua, hake Merluccius merluccius, megrim Lepidorhombus whiffiagonis, and whiting Merlangius merlangus) using stomach-content and bottom-trawl survey data for the period 1982 to 1995. Blue whiting Micromesistius poutassou were consumed more often during the summer months, whereas mackerel Scomber scombrus and Trisopterus spp. (poor cod T minutus, Norway pout T esmarkii, and bib T luscus) were found more often in predator stomachs during the winter half-year. On a spatial scale, blue whiting was consumed over the shelf edge, in accordance with their higher densities in the environment, while mackerel,... |
| Tipo: Text |
Palavras-chave: Spatial distribution; Season; Celtic Sea; Preference; Stomach contents; Diet. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-3619.pdf |
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| Rochet, Marie-joelle; Collie, Jeremy S.; Trenkel, Verena. |
| Competition and predation can play different roles in mediating the influence of external pressures, such as fishing or environmental variations, on marine communities. Pressure effects propagate through food webs along predation links. These predator-prey interactions may result in trophic cascades, but they can be buffered by competitive interactions. We investigated these mechanisms by taking a functional-group approach. Are functional groups affected by external pressures in a predictable way? Within functional groups, do all species respond in the same way, or does competitive release allow for compensation among species? We constructed a simple community model, with functional groups connected by predation links. Loop analysis was used to make... |
| Tipo: Text |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00154/26492/25465.pdf |
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| Marandel, Florianne; Biais, Gerard; Bidault, Adeline; Charrier, Grégory; Cornette, Florence; Lapegue, Sylvie; Laroche, Jean; Le Cam, Sabrina; Stephan, Eric; Trenkel, Verena; Lorance, Pascal. |
| At the ecosystem level, sustainable exploitation of fisheries resources depends not only on the status of target species but also on that of bycatch species, some of which are even more sensitive to exploitation. This is the case for a number of elasmobranchs (skates, rays and sharks) species whose abundance declined during the 20th century. Further, the biology of elamobranchs is still poorly known and traditional fisheries stock assessment methods using fisheries catches and scientific survey data for estimating abundance are expensive or even inapplicable due to the small numbers observed. The GenoPopTaille project attempts to apply to the case of the thornback ray (Raja clavata) recent genetic-based methods for absolute population abundance estimation... |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00343/45439/44960.pdf |
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| Trenkel, Verena; Handegard, Nils Olav; Weber, Thomas C.. |
| Active- and passive-acoustic methods are widely used tools for observing, monitoring, and understanding marine ecosystems. From 25 to 28 May 2015, 214 scientists from 31 nations gathered for an ICES symposium on Marine Ecosystem Acoustics (SoME Acoustics) to discuss three major themes related to acoustic observations of marine ecosystems: (i) recent developments in acoustic and platform technologies; (ii) acoustic characterisation of aquatic organisms, ecosystem structure, and ecosystem processes; and (iii) contribution of acoustics to integrated ecosystem assessments and management. The development of, and access to new instruments, such as broad bandwidth systems, enables insightful ecological studies and innovative management approaches. Unresolved... |
| Tipo: Text |
Palavras-chave: Acoustics; Broadband; Multi-frequency; Passive and active acoustics; Ecosystem approach to management; Ecosystem monitoring; Pelagic ecosystem; Echosounder; Sonar. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00347/45820/45921.pdf |
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| Trenkel, Verena; Berger, Laurent; Bourguignon, Sebastien; Doray, Mathieu; Fablet, Ronan; Masse, Jacques; Mazauric, Valerie; Poncelet, Cyrille; Quemener, Gael; Scalabrin, Carla; Villalobos, Hector. |
| This paper provides an overview of the progress Ifremer has made recently in fisheries acoustics and the study of small pelagic fish by: i) pushing observation frontiers using a range of platforms including an autonomous underwater vehicle, AUV, ii) developing measuring instruments and methods and iii) studying fish distributions. Presently, information from several frequencies of single-beam echosounders is routinely collected together with data from the ME70 multibeam echosounder. For onboard data acquisition control the HERMES software was developed. The new MOVIES 3D software includes modules for simultaneous realistic 3D visualisation and post-processing such as bottom detection, school extraction and calculation of descriptors and integration of all... |
| Tipo: Text |
Palavras-chave: Multibeam echosounder; Oceanographic AUV; Pelagic fish; Fisheries acoustics. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00000/11165/7517.pdf |
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| Greenstreet, Simon P. R.; Fraser, Helen M.; Rogers, Stuart I.; Trenkel, Verena; Simpson, Stephen; Pinnegar, John K.. |
| Broader ecosystem management objectives for North Sea demersal fish currently focus on restoring community size structure. However, most policy drivers explicitly concentrate on restoring and conserving biodiversity, and it has not yet been established that simply restoring demersal fish size composition will be sufficient to reverse declines in biodiversity and ensure a generally healthy community. If different aspects of community composition, structure, and function vary independently, then to monitor all aspects of community general health will require application of a suite of metrics. This assumes low redundancy among the metrics used in any such suite and implies that addressing biodiversity issues specifically will require explicit management... |
| Tipo: Text |
Palavras-chave: Community health; Community size structure; Ecosystem approach to management; Life-history-trait metrics; Metric suites; Species diversity; State indicators. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00056/16709/14201.pdf |
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| Huse, G.; Mackenzie, B. R.; Trenkel, Verena; Doray, Mathieu; Nottestad, L.; Oskarsson, G.. |
| The North Atlantic is a productive marine region which has supported important commercial fisheries for centuries. Many of these fisheries have exploited the pelagic species, including herring, blue whiting and tuna. Here we present data on the distribution of herring and blue whiting based on the international ecosystem survey in the Nordic Seas (IESNS), the bottom trawl survey in the Bay of Biscay and Celtic Sea (EVHOE) and the pelagic survey in the Bay of Biscay (PELGAS). We also present catch data on bluefin tuna, which has been depleted for decades but historically used to be a key predator on the other pelagic stocks during summer. The results show that there were substantial changes in the herring and blue whiting distribution during the 1990s and... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00276/38675/37150.pdf |
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| Battaglia, Andre; Trenkel, Verena; Rochet, Marie-joelle. |
| The end effect in trawl catches is defined as the proportion of the fish catch taken during shooting and hauling of the net, a period excluded from that nominally referred to as haul duration. If important, this effect will lead to biased abundance estimates, because the swept area will be underestimated. An experimental survey was carried out to compare catch numbers obtained in standard research 30-min hauls with those from 0-min hauls, the latter referring to the trawl being hauled as soon as the trawl geometry stabilized on the seabed. Average catch ratios (0-min/30-min hauls) ranged from 0.05 (s.d. 0.06) for sole to 0.34 (s.d. 0.64) for hake, indicating that the end effect might be more important and more variable for highly mobile species. As a... |
| Tipo: Text |
Palavras-chave: Trawl survey; Bias; Abundance index. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/2006/publication-1686.pdf |
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| Registros recuperados: 99 | |
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