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| Registros recuperados: 99 | |
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| Brind'Amour, Anik; Rochet, Marie-joelle; Ordines, Francesc; Hosack, Geoff; Berthele, Olivier; Merigot, Bastien; Carbonara, Pierluigi; Follesa, Maria Cristina; Jadaud, Angelique; Lefkaditou, Evgenia; Maiorano, Porzia; Peristeraki, Panagiota; Mannini, Alessandro; Rabiller, Manuella; Spedicato, Maria Teresa; Tserpes, George; Trenkel, Verena. |
| Functional groups are sets of species that play a similar role in a food web. We defined functional groups of fish species based on their morphological characteristics, while using expert knowledge for invertebrates. We measured 9 morphological traits of 72 fish species, and carried out multivariate analyses to assign fish species to functional groups. The analysis identified 9 trait-based fish functional groups to which were added 3 expert-based invertebrate functional groups. The habitat (position in the water column) and potential diet of each group were identified from the literature. Using the MEDITS bottom trawl survey data collected at 10 to 800 m depth, we calculated relative change in the 12 fish and invertebrate functional group biomasses for 12... |
| Tipo: Text |
Palavras-chave: Morphological traits; Community models; Functional network; Functional groups; Mediterranean Sea; Temporal trends; Fish; Shellfish. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00363/47382/47475.pdf |
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| Bertrand, Jacques; Cochard, Marie-laure; Coppin, Franck; Leaute, Jean-pierre; Lobry, Jeremy; Mahe, Jean-claude; Morin, Jocelyne; Poulard, Jean-charles; Rochet, Marie-joelle; Schlaich, Ivan; Souplet, Arnauld; Trenkel, Verena; Verin, Yves; SIH-C. |
| The integration of fishing management into the ecosystemic approach has been recommended for many years by international consultative bodies; it is also written into international conventions and agreements. The implementation of the ecosystemic approach involves the development of programmes for monitoring exploited ecosystems in order to measure the effects of management steps. Plotting the results of these observations for operational reasons requires formalizing summary performance indicators. IFREMER has carried out halieutic observation campaigns for some twenty years along the coasts of France from oceanographic ships and chartered ships. The objective of these campaigns is to produce abundance indices of species that are of halieutic interest.... |
| Tipo: Text |
Palavras-chave: Ecosystem; Indicating; Scientific survey; Scientific research; Fishing; English Channel; Bay of Biscay; France; Shellfish; Fish; Invertébrés; Poissons; Ecosystème; Indicateur; Campagne océanographique; Recherche scientifique; Pêche halieutique; Pêche; Mer du nord; Golfe de gascogne; Manche; France. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/rapport-2327.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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| Marandel, Florianne; Lorance, Pascal; Andrello, Marco; Charrier, Gregory; Le Cam, Sabrina; Lehuta, Sigrid; Trenkel, Verena. |
| Studying demographic and genetic connectivity can help assessing marine meta-population structure. Rays and skates have no larval phase hence population connectivity can only result from active movement of individuals. Using thornback ray (Raja clavata) in European waters as a case study, demographic and genetic connectivity were studied for 11 putative populations for unequal population abundances and two hypotheses of dispersal rates. Genetic simulation results highlighted three large meta-populations: in the Mediterranean, around the Azores and on the Northeast Atlantic shelf. Demographic results highlighted a finer population structure indicating that several pairs of putative populations might be demographically linked. Results were highly... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00404/51535/52125.pdf |
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| Trenkel, Verena; Rochet, Marie-joelle. |
| Using indicator time series for assessment and management requires methods for characterising recent time trends. We propose an approach where first the indicator time series is smoothed using a generalised additive model with optimal selection of the degree of smoothness. Second an intersection-union test is carried out using two test statistics which are the occurrence of the global maximum (or minimum) within the most recent years and the signs of the estimated annual first derivatives of the smoothed indicator times series during the same period, including years with missing data. The proposed test is applied to fish abundance indices for the North Sea, for which it is they are able to pick up changes happening during the last 3-5 years in contrast to... |
| Tipo: Text |
Palavras-chave: Composite test; Assessment; Fisheries management; Metrics; Time trend. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6234.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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| 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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| 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; 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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| Marandel, Florianne; Charrier, Gregory; Lamy, Jean-baptiste; Le Cam, Sabrina; Lorance, Pascal; Trenkel, Verena. |
| Effective population size (Ne) is a key parameter of population genetics. However, Ne remains challenging to estimate for natural populations as several factors are likely to bias estimates. These factors include sampling design, sequencing method, and data filtering. One issue inherent to the restriction site‐associated DNA sequencing (RADseq) protocol is missing data and SNP selection criteria (e.g., minimum minor allele frequency, number of SNPs). To evaluate the potential impact of SNP selection criteria on Ne estimates (Linkage Disequilibrium method) we used RADseq data for a nonmodel species, the thornback ray. In this data set, the inbreeding coefficient FIS was positively correlated with the amount of missing data, implying data were missing... |
| Tipo: Text |
Palavras-chave: Effective population size; Linkage disequilibrium; NeEstimator; RADseq; Skates and rays. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00607/71934/70628.pdf |
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| Trenkel, Verena. |
| In this poster I will present the results from text mining analyses of the abstracts of the current and previous ICES acoustic symposia as well as WGFAST working group reports. By creating and comparing lists of the most common words in each symposium and WGFAST reports it will be possible to measure the overall change in breadth and possible shifts in focus in the field of marine ecosystem acoustics. The same analysis will also identify the contribution of WGFAST to the progress in the field. An analysis of the authors will provide means to characterize the structure of the research fellow communities participating in ICES acoustic symposia and WGFAST meetings. |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00598/71042/69352.pdf |
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| Trenkel, Verena; Berger, Laurent. |
| Fisheries acoustic instruments provide information on four major groups in aquatic ecosystems: fish with and without swim bladder (tertiary and quaternary consumers), fluidlike zooplankton (secondary consumers) and small gas bearing organisms such as larval fish and phytoplankton (predominantly primary producers). We entertain that this information is useable to describe the spatial structure of organism groups in pelagic ecosystems. The proposal we make is based on a multi-frequency indicator that synthesises in a single metric the shape of the acoustic frequency response of different organism groups, i.e. the dependence of received acoustic backscattered energy on emitting echosounder frequency. We demonstrate the development and interpretation of the... |
| Tipo: Text |
Palavras-chave: Acoustics; Frequency response curve; Monitoring; EOF; Ecosystem state. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00128/23886/21848.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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| Trenkel, Verena; Lorance, Pascal; Berthele, Olivier; Ferrant, Anthony; Le Piver, David; Rochet, Marie-joelle. |
| The data come from bait experiments that were carried out at three study sites (Meriadzek Terrace, terrace located between the canyon of Belle Île and the canyon of St Nazaire referred to as St Nazaire Terrace, and Belle Île Canyon) on the continental slope of the Bay of Biscay during the VITAL cruise in late August and early September 2002 using the ROV Victor 6000. A full description of the experiments and results can be found in Trenkel and Lorance (2011). The depth range 1100 – 1500 m was investigated in all sites by perpendicular strip transects starting from the deepest point and moving up slope (see full description in Trenkel et al 2004). Bait experiments were carried out at all three sites at regular intervals (every 12 hours) along the... |
| Tipo: Dataset |
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| Ano: 2015 |
URL: http://dx.doi.org/10.17882/39746 |
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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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| Trenkel, Verena; Rochet, Marie-joelle; Mahevas, Stephanie. |
| Norway lobster, Nephrops norvegicus (L.) was found to show diel activity patterns with more individuals outside their burrows at dawn and dusk in the Bay of Biscay in August 2004 and catchabilities were higher at these times. Using data from an onboard observer programme of Nephrops trawlers in 2002-2005, we investigated whether the expected variability in catchability was visible in commercial catches. Catch numbers per haul varied spatially and between months but no signal for diel variations was found. Fishing strategies developed by the Nephrops trawlers had several components. On a seasonal level they started around sunrise. On a haul level, haul duration decreased from haul to haul, with the longest hauls taking place at the time of highest... |
| Tipo: Text |
Palavras-chave: Time of day; Fishing strategy; Diel activity patterns; Catchability. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2618.pdf |
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| Registros recuperados: 99 | |
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