Consulta: creatorFacets:"Trenkel, Verena"
Registros recuperados: 99
Data/hora: 14/06/2024 03:40:25

Modelling the fishing costs of French commercial vessels in the Bay of Biscay
Provedor de dados: 5
Autores: 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

Estimating Synaphobranchus kaupii densities: Contribution of fish behaviour to differences between bait experiments and visual strip transects
Provedor de dados: 5
Autores: 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

How to provide scientific advice for ecosystem-based management now
Provedor de dados: 5
Autores: 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

From model-based prescriptive advice to indicator-based interactive advice
Provedor de dados: 5
Autores: 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

Combining quantitative and qualitative models to identify functional groups for monitoring changes in the Bay of Biscay continental shelf exploited foodweb
Provedor de dados: 5
Autores: 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

Choosing survey time series for populations as part of an ecosystem approach to fishery management
Provedor de dados: 5
Autores: 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

Trend analysis of indicators: a comparison of recent changes in the status of marine ecosystems around the world
Provedor de dados: 5
Autores: 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

Ecosystem trends: evidence for agreement between fishers' perceptions and scientific information
Provedor de dados: 5
Autores: 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

Méthodes d'évaluation des ressources marines vivantes pour une exploitation durable
Provedor de dados: 5
Autores: 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

Different surveys provide similar pictures of trends in a marine fish community but not of individual fish populations
Provedor de dados: 5
Autores: 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

Changes in Brain Monoamines Underlie Behavioural Disruptions after Zebrafish Diet Exposure to Polycyclic Aromatic Hydrocarbons Environmental Mixtures
Provedor de dados: 5
Autores: 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

Grands invertébrés et poissons observés par les campagnes scientifiques. Atlas de distribution. Bilan 2008
Provedor de dados: 5
Autores: 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

Spatial and temporal structure of predator-prey relationships in the Celtic Sea fish community
Provedor de dados: 5
Autores: 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

How Do Fishing and Environmental Effects Propagate Among and Within Functional Groups?
Provedor de dados: 5
Autores: 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
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00154/26492/25465.pdf

GenoPopTaille. Moving stock assessment into the future
Provedor de dados: 5
Autores: 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
Ano: 2016
URL: http://archimer.ifremer.fr/doc/00343/45439/44960.pdf

Observing the ocean interior in support of integrated management
Provedor de dados: 5
Autores: 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

Overview of recent progress in fisheries acoustics made by Ifremer with examples from the Bay of Biscay
Provedor de dados: 5
Autores: 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

Redundancy in metrics describing the composition, structure, and functioning of the North Sea demersal fish community
Provedor de dados: 5
Autores: 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

Spatially explicit estimates of stock sizes, structure and biomass of herring and blue whiting, and catch data of bluefin tuna
Provedor de dados: 5
Autores: 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
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00276/38675/37150.pdf

Estimating end effects in trawl catches
Provedor de dados: 5
Autores: 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

Use of morphological characteristics to define functional groups of predatory fishes in the Celtic Sea
Provedor de dados: 5
Autores: Reecht, Yves; Rochet, Marie-joelle; Trenkel, Verena; Jennings, S.; Pinnegar, J. K.
An ecomorphological method was developed, with a focus on predation functions, to define functional groups in the Celtic Sea fish community. Eleven functional traits, measured for 930 individuals from 33 species, led to 11 functional groups. Membership of functional groups was linked to body size and taxonomy. For seven species, there were ontogenetic changes in group membership. When diet composition, expressed as the proportions of different prey types recorded in stomachs, was compared among functional groups, morphology-based predictions accounted for 28-56% of the interindividual variance in prey type. This was larger than the 12-24% of variance that could be explained solely on the basis of body size. (C) 2013 The Fisheries Society of the British Isles
Tipo: Text
Palavras-chave: Ecomorphology; Functional traits; Predation strategy; Trophic functions.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00152/26294/24831.pdf

Fishing fleet typology, economic dependence, and species landing profiles of the French fleets in the Bay of Biscay, 2000-2006
Provedor de dados: 5
Autores: Daures, Fabienne; Rochet, Marie-joelle; Van Iseghem, Sylvie; Trenkel, Verena.
Thirty French fleets fishing primarily in the Bay of Biscay were defined based on techno-economic input criteria: i) 18 fishing gear or gear combinations ii) the location of fishing grounds visited during a year (&lt;12 nautical miles from coast, beyond 12 nm or both) and iii) total vessel length (&lt;20 m for trawlers and other gears &lt;24 m). The fleets were then characterised in terms of horse power, economic dependence on a list of nine dominant commercial species (sole, Nephrops, sea bass, hake, monkfish, anchovy, cuttlefish, sardine and squid) and their contribution to the landings of these species from the Bay of Biscay. Most fleets derived the majority of their income from one or two among the nine species. Species dependencies changed little...
Tipo: Text
Palavras-chave: Fishing methods; Fishing vessels; Fleet dynamics; Mixed fisheries; Catch distribution; Economy; Atlantic Ocean.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/00000/11172/7530.pdf

Testing CPUE-derived spatial occupancy as an indicator for stock abundance: application to deep-sea stocks
Provedor de dados: 5
Autores: Trenkel, Verena; Beecham, Jonathan A.; Blanchard, Julia L.; Edwards, Charles T. T.; Lorance, Pascal.
The status of an exploited population is ideally determined by monitoring changes in abundance and distributional range and pattern over time. Area of occupancy is a measure of the current distribution. Unfortunately, for many populations, scientific abundance and distribution information is not readily available. To evaluate the reliability of commercial fishing data for deriving occupancy indicators that could serve as proxies for stock abundance, we investigated four questions: 1) Occupancy changes with stock biomass, but is this change strong enough to make occupancy a sensitive indicator of population biomass? 2) Fishing boats follow fish, but when does such activity alter the positive macroecological relationship between occupancy and abundance? 3)...
Tipo: Text
Palavras-chave: Catch per unit effort; Spatial patterns; Macroecology; Fisheries management; Marine Strategy Framework Directive; MSFD.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00176/28759/27232.pdf

The new fisheries multibeam echosounder ME70: description and expected contribution to fisheries research
Provedor de dados: 5
Autores: 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

Censored catch data in fisheries stock assessment
Provedor de dados: 5
Autores: Hammond, T; Trenkel, Verena.
Landings statistics can be lower than true catches because many fish are discarded or landed illegally. Since many discards do not survive, treating landings as true catches can lead to biased stock assessments. This paper proposes treating catch as censored by bounding it below by the landings, L, and above by cL (for scalar c &gt; 1), We demonstrate the approach with a simulation study, using a Schaefer surplus production model. Parameters were estimated in a Bayesian framework with BUGS software using two sets of priors. Both the traditional true-catch method and a survey-and-effort method (which was landings free) performed worse on average than the censored approach, as measured by the Bayes risk associated with estimates of maximum sustainable yield...
Tipo: Text
Palavras-chave: Stock assessment; Misreporting; Discarding; Censored data.
Ano: 2005
URL: http://archimer.ifremer.fr/doc/2005/publication-641.pdf

Assessment of impacts from human activities on ecosystem components in the Bay of Biscay in the early 1990s
Provedor de dados: 5
Autores: Lorance, Pascal; Bertrand, Jacques; Brind'Amour, Anik; Rochet, Marie-joelle; Trenkel, Verena.
The ecosystem-based approach to fisheries management and, more specifically, the European Marine Strategy Framework Directive require the assessment of the state and dynamics of an ecosystem in order to determine suitable management strategies. This paper takes an analytical approach to assess the state of the Bay of Biscay ecosystem in the early 1990s, chosen as a period of reference because key monitoring data series have been collected since then. To assess the state of the ecosystem, the pressures exerted by six broad categories of human activities were examined. A literature review of the ecosystem components was made and a component tree was tailored according to data availability. Data rich components were subdivided into subcomponents for their...
Tipo: Text
Palavras-chave: Reference state; Ecosystem based management; Human pressure; Inventory; Atlantic Ocean.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/00000/11164/7520.pdf

Density estimator for strip transects when animals show directional movement and observation speed is slow
Provedor de dados: 5
Autores: Trenkel, Verena.
A strip transect population density estimator and its variance are presented. These take into account stochastic survey velocity as well as stochastic swimming velocity and non-random swimming direction of the surveyed animals. The estimator is mainly of interest for surveys of animals with a directional swimming behaviour and swimming velocities similar to the survey velocity, such as those carried out by divers or remotely operated vehicles.
Tipo: Text
Palavras-chave: Variance estimators; Abundance estimation; Bias; Fish movement; Visual transects.
Ano: 2003
URL: http://archimer.ifremer.fr/doc/2003/publication-6655.pdf

Identifying marine pelagic ecosystem management objectives and indicators
Provedor de dados: 5
Autores: Trenkel, Verena; Hintzen, Niels T.; Farnsworth, Keith D.; Olesen, Christian; Reid, David; Rindorf, Anna; Shephard, Samuel; Dickey-collas, Mark.
International policy frameworks such as the Common Fisheries Policy and the European Marine Strategy Framework Directive define high-level strategic goals for marine ecosystems. Strategic goals are addressed via general and operational management objectives. To add credibility and legitimacy to the development of objectives, for this study stakeholders explored intermediate level ecological, economic and social management objectives for Northeast Atlantic pelagic ecosystems. Stakeholder workshops were undertaken with participants being free to identify objectives based on their own insights and needs. Overall 26 objectives were proposed, with 58% agreement in proposed objectives between two workshops. Based on published evidence for pressure-state links,...
Tipo: Text
Palavras-chave: Ecosystem-based management; Marine pelagic community; Management objective; MSFD; CFP.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00251/36214/34774.pdf

A two-stage biomass random effects model for stock assessment without catches: What can be estimated using only biomass survey indices?
Provedor de dados: 5
Autores: 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 (&gt; 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

Insights from genetic and demographic connectivity for the management of rays and skates
Provedor de dados: 5
Autores: 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
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00404/51535/52125.pdf

Deriving blue ling abundance indices from industry haul by haul data
Provedor de dados: 5
Autores: Lorance, Pascal; Pawlowski, Lionel; Trenkel, Verena.
A database of tallybooks, from skippers' own logbooks, provided by the French industry involved in deep-water fishing to the west of the British Isles was used to standardise blue ling Landings per Unit of Effort (LPUEs). The data covered the years 1992-2008 with more extensive data for the period 2000-2007. For each haul, landings by species, tow duration, depth and location were reported. Compared to EU logbooks, this database is on a haul by haul basis instead of being aggregated by fishing sub-trips combining hauls from the same day, ICES rectangle and gear. Moreover, it includes depth, which is a major factor for catch rates in deepwater fisheries. LPUEs were estimated from Generalised Additive Models (GAMs) with depth, vessel, statistical rectangle...
Tipo: Text
Palavras-chave: Molva dypterygia; Abundance indices; Fishing strategy; Tweedie distribution.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/00102/21330/18953.pdf

Precision and accuracy of fish length measurements obtained with two visual underwater methods
Provedor de dados: 5
Autores: Rochet, Marie-joelle; Cadiou, Jean-francois; Trenkel, Verena.
During the VIITAL cruise in the Bay of Biscay in summer 2002, two devices for measuring the length of swimming fish were tested: 1) a mechanical crown that emitted a pair of parallel laser beams and that was mounted on the main camera and 2) an underwater auto-focus video camera. The precision and accuracy of these devices were compared and the various sources of measurement errors were estimated by repeatedly measuring fixed and mobile objects and live fish. It was found that fish mobility is the main source of error for these devices because they require that the objects to be measured are perpendicular to the field of vision. The best performance was obtained with the laser method where a video-replay of laser spots (projected on fish bodies) carrying...
Tipo: Text
Palavras-chave: Auto focus method; Laser method; Error estimation; Measurement methods; Fish lenght.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/publication-978.pdf

Interactions between fishing strategies of nephrops trawlers in the Bay of Biscay and Norway lobster diel activity patterns
Provedor de dados: 5
Autores: 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

Exploring the abundance-occupancy relationships for the Georges Bank finfish and shellfish community from 1963 to 2006
Provedor de dados: 5
Autores: Frisk, Michael G.; Duplisea, Daniel E.; Trenkel, Verena.
Abundance-occupancy (A-O) patterns were explored temporally and spatially for the Georges Bank finfish and shellfish community to evaluate long-term trends in the assemblage structure and to identify anthropogenic and environmental drivers impacting the ecosystem. Analyses were conducted for 32 species representing the assemblage from 1963 to 2006 using data from the National Marine Fisheries Service's annual autumn bottom trawl survey. For individual species, occupancy was considered the proportion of stations with at least one individual present, and abundance was estimated as the mean annual number of fish captured per station. Intraspecific relationships were estimated to provide information on utilization of space by a species. Multispecies...
Tipo: Text
Palavras-chave: Abundance-occupancy relationships; Commercial catchability; Community ecology; Exploitation; Finfish; Fishing; Georges Bank; Habitat fragmentation; Hyperstability; Resilience; Shellfish.
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00033/14397/14043.pdf

Poissons et invertébrés au large des côtes de France. Indicateurs issus des pêches scientifiques. Bilan 2004
Provedor de dados: 5
Autores: 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

Optimisation des échantillonnages biologiques (suivis long-terme, évaluations de restauration) en grands fleuves et autres milieux
Provedor de dados: 5
Autores: Lamouroux, N; Cauvy-fraunie, S; Vaudor, L.; Olivier, J.m; Trenkel, Verena; Maire, A; Forcellini, M; Roset, N.
Studies of the efficiency vs. the cost of long-term biological monitoring strategies are particularly infrequent and needed in large rivers. We used recent studies concerning the long-term monitoring of fish and macroinvertebrates in the Rhône River to discuss the potential and limits of monitoring strategies in large rivers and other environments. A first study is a numerical analysis of the probability to detect changes in fish abundance after flow restoration in the river. A second study concerns the detection of "most expected" relationships in annual fish time series, such as fish cohort follow-ups. It involves a comparison of the Rhône results with those obtained in smaller rivers (where sampling is easier) or in the ocean (where sampling is even...
Tipo: Text
Palavras-chave: Abundance time series; Ecological restoration; Monitoring design; Statistical power analysis.
Ano: 2018
URL: http://archimer.ifremer.fr/doc/00443/55468/56990.pdf

Investigating trophic-level variability in Celtic Sea fish predators
Provedor de dados: 5
Autores: Chassot, E; Rouyer, Tristan; Trenkel, Verena; Gascuel, D.
The trophic level mean and variance, and the degree of omnivory for five Celtic Sea fish predators were estimated using a database of stomach content records characterized by a high level of taxonomic resolution. The predators occupied a high position in the food web, i.e. 4.75 for Atlantic cod Gadus morhua, 444 for haddock Melanogrammus aeglefinus, 4.88 for European hake Merluccius merluccius, 5.00 for megrim Lepidorhombus whiffiagonis and 5.27 for whiting Merlangius merlangus. The level of taxonomic resolution of the prey did not greatly affect mean T-L predator values; an effect on variance was evident, low resolution masking intra-population variability in T-L. Generalized additive models (GAM) were used to explain the variability of predator T-L...
Tipo: Text
Palavras-chave: Trophic level; Predation; Omnivory; Indicator; GAM; Food web.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-4699.pdf

Environmental drivers explain regional variation of changes in fish and invertebrate functional groups across the Mediterranean Sea from 1994 to 2012
Provedor de dados: 5
Autores: 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

Grands invertébrés et poissons observés par les campagnes scientifiques. Bilan 2007
Provedor de dados: 5
Autores: Bertrand, Jacques; Brind'Amour, Anik; Cochard, Marie-laure; Coppin, Franck; Leaute, Jean-pierre; Lorance, Pascal; Mahe, Jean-claude; Morin, Jocelyne; Poulard, Jean-charles; Rochet, Marie-joelle; Schlaich, Ivan; Souplet, Arnauld; Trenkel, Verena; Verin, Yves.
The ecosystems exploited by fishing are complex. The species which are sought after and their distribution rely on numerous processes, in time and space. The understanding of marine ecosystems requires important means and diverse information including those of professional fishing and scientific cruises. At first, scientific fishing cruises aimed to explore marine fauna and discover new halieutic resources. They were in line with the exploration cruises carried out by Prince Albert 1st of Monaco at the end of the XIXth century. However, since the beginning of the 1970s, they have been focusing on the quantification of the resources exploited by fishing. [...] After a series of "Understanding keys" aimed at helping the reader understand the methodology and...
Tipo: Text
Palavras-chave: Mediterranean Sea; Bay of Biscay; English Channel; North Sea; France; Communities; Populations; Fishery science; Indicators; Bulletin; Méditerranée; Golfe de Gascogne; Manche; Mer du Nord; France; Pêche; Campagnes à la mer; Communautés; Populations; Halieutique; Indicateurs; Bulletin.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/rapport-6160.pdf

Evaluating the potential impact of fishing on demersal species in the Bay of Biscay using simulations and survey data
Provedor de dados: 5
Autores: Ravard, David; Brind'Amour, Anik; Trenkel, Verena.
Fishing affects fish populations through direct and indirect effects. It can change size structures and/or modify population mean weights. Reference values are thus needed to assess the status of populations in exploited ecosystems. These reference values can either be set by a historical approach, i.e. using information from before the onset of exploitation or overexploitation, or by a simulation approach. Using a model based on life-history parameters, we predicted population mean weights and length structures at equilibrium (in the absence of fishing and for fishing equal to different fishing mortalities) which we compared with contemporary data collected during scientific surveys in the Bay of Biscay. Contemporary mean weights were 88% to 30% smaller...
Tipo: Text
Palavras-chave: Indicators; Fishing impacts; Ecosystem based management; Fish community; Reference points; Northeast Atlantic.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00188/29968/28485.pdf

Utility of mixed effects models to inform the stock structure of whiting in the Northeast Atlantic Ocean
Provedor de dados: 5
Autores: Barrios, Alexander; Ernande, Bruno; Mahe, Kelig; Trenkel, Verena; Rochet, Marie-joelle.
Stock structure of whiting (Merlangius merlangus) in the North East Atlantic is unclear. This study uses mixed effects models to analyse growth variability as a way to investigate stock identification. Growth trajectories for 634 individuals and length-at-age data for 78,686 individuals were analysed for spatial coherence and temporal synchrony in the parameters of the von Bertalanffy growth model. Growth was found to differ among most ICES divisions, and temporal fluctuations were poorly synchronized between areas. This study illustrates how growth analyses can contribute to stock identification, in addition to other data.
Tipo: Text
Palavras-chave: Growth; Whiting; North East Atlantic; Otolith; Von Bertalanffy growth model; Mixed effects models.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00373/48415/48810.pdf

Underwater acoustics for ecosystem-based management: state of the science and proposals for ecosystem indicators
Provedor de dados: 5
Autores: 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

Capacity management, not stock status or economics, drives fleet dynamics in the Bay of Biscay ecosystem on a decadal time scale
Provedor de dados: 5
Autores: Rochet, Marie-joelle; Daures, Fabienne; Trenkel, Verena.
This paper introduces a semiqualitative approach to analyse the joint dynamics of fleets and stocks in a multispecies, multifleet fishery. We ask whether changes in fleets affect resource dynamics and whether trends in resource influence fleet dynamics more than external drivers do. External drivers include vessel buyback, fuel price, and fish prices, as well as environmental fluctuations. Resource status is measured by abundance and length metrics; fleet capacity is measured by total horse power, and economic metrics such as profitability and earnings are examined as well. A maximum likelihood approach is used to identify the combined metric trends with the largest support in the data. The approach is applied to the French Bay of Biscay fisheries in...
Tipo: Text
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00076/18730/16336.pdf

Pelagic habitat: exploring the concept of good environmental status
Provedor de dados: 5
Autores: Dickey-collas, Mark; Mcquatters-gollop, Abigail; Bresnan, Eileen; Kraberg, Alexandra C.; Manderson, John P.; Nash, Richard D. M.; Otto, Saskia A.; Sell, Anne F.; Tweddle, Jacqueline F.; Trenkel, Verena.
Marine environmental legislation is increasingly expressing a need to consider the quality of pelagic habitats. This paper uses the European Union marine strategy framework to explore the concept of good environmental status (GES) of pelagic habitat with the aim to build a wider understanding of the issue. Pelagic ecosystems have static, persistent and ephemeral features, with manageable human activities primarily impacting the persistent features. The paper explores defining the meaning of "good", setting boundaries to assess pelagic habitat and the challenges of considering habitat biodiversity in a moving medium. It concludes that for pelagic habitats to be in GES and able to provide goods and services to humans, three conditions should be met: (i) all...
Tipo: Text
Palavras-chave: Marine strategy framework directive; MPA; Pelagic habitats; Plankton; Seascape.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00414/52596/53551.pdf

Impacts de l’extraction sélective d’espèces sur les populations, les communautés et les réseaux trophiques. Sous-région marine Méditerranée occidentale. Evaluation initiale DCSMM.
Provedor de dados: 5
Autores: Trenkel, Verena.
Tipo: Text
Palavras-chave: Méditerranée; Extraction sélective; Espèces; Impacts; Populations; Communautés; Réseau trophique.
Ano: 2012
URL: https://archimer.ifremer.fr/doc/00331/44251/43820.pdf

Observations for Synaphobranchus kaupii from bait experiments carried out in the Bay of Biscay in 2002 using ROV Victor 6000
Provedor de dados: 5
Autores: 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
Ano: 2015
URL: http://dx.doi.org/10.17882/39746

Estimating gear efficiency in a combined acoustic and trawl survey, with reference to the spatial distribution of demersal fish
Provedor de dados: 5
Autores: Doray, Mathieu; Mahevas, Stephanie; Trenkel, Verena.
Few analyses have been performed to estimate the efficiency of trawls targeting demersal fish using the ratio of catches and acoustic densities. In summer 2006, acoustic and fishing data were collected simultaneously over 3 d by three fishing vessels equipped with identical pelagic trawls in the Bay of Biscay. Variography identified moderate spatial autocorrelation in the acoustic backscatter at a mean scale of 3 km, a scale slightly smaller than the mean haul length (3.5 km), indicating that fish horizontal availability did not influence trawl efficiency. Acoustic backscattering densities expressed as nautical area scattering coefficients (NASCs) recorded in the trawled layer were compared with equivalent NASC (ENASC) values calculated from the species...
Tipo: Text
Palavras-chave: Availability; Bay of Biscay; Catchability; Generalized linear model; Geostatistics; Hake; Vulnerability.
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00002/11372/7980.pdf

Effects of density dependence, zooplankton and temperature on blue whiting     Micromesistius poutassou     growth
Provedor de dados: 5
Autores: Trenkel, Verena; Lorance, Pascal; Fassler, S. M. M.; Hoines, A. S.
Blue whiting Micromesistius poutassou mean total length at age in the north-east Atlantic Ocean was found to vary by around ±6% during the period 2004–2011 and mean mass at age by ±22% during the years 1981–2013. Linear modelling provided strong evidence that these phenotypic growth variations can be explained by trophic conditions, mainly negative density dependence and also food availability, and a negative long-term temperature effect on asymptotic siz
Tipo: Text
Palavras-chave: Environmental effect; Food availability; Trophic conditions; Von Bertalanffy.
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00279/39037/37623.pdf

Combining time trends in multiple metrics for identifying persistent changes in population processes or environmental stressors
Provedor de dados: 5
Autores: Trenkel, Verena; Rochet, Marie-joelle.
P&gt;1. Metrics have become a standard way for summarizing environmental monitoring results. Different metrics react differently to natural variations and human-induced stressors. We suggest that combined analysis of time trends in selected biological metrics allows identification of biological processes (e.g. individual growth, mortality or recruitment) that have changed (increased or decreased) persistently. Alternatively, time trends in the abundance of sensitive species could indicate changes in environmental stressors. 2. We calculate the joint likelihood of time trends in three metrics and use it to evaluate the evidence in the data for different combinations of metric time trends. A simulation study provides guidelines for interpreting...
Tipo: Text
Palavras-chave: Generalized additive model; Indicators; Likelihood principle; Quadratic programming; Survey data.
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00008/11926/8988.pdf

A bootstrap method for estimating bias and variance in statistical fisheries modelling frameworks using highly disparate datasets
Provedor de dados: 5
Autores: Elvarsson, B. P.; Taylor, L.; Trenkel, Verena; Kupca, V.; Stefansson, G.
Statistical models of marine ecosystems use a variety of data sources to estimate parameters using composite or weighted likelihood functions with associated weighting issues and questions on how to obtain variance estimates. Regardless of the method used to obtain point estimates, a method is required for variance estimation. A bootstrap technique is introduced for the evaluation of uncertainty in such models, taking into account inherent spatial and temporal correlations in the datasets, which are commonly transferred as assumptions from a likelihood estimation procedure into Hessian-based variance estimation procedures. The technique is demonstrated on a real dataset and the effects of the number of bootstrap samples on estimation bias and variance...
Tipo: Text
Palavras-chave: Bootstrapping; Correlated data; Fish population dynamics; Non-linear models.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00193/30459/29913.pdf

Space-time modelling of blue ling for fisheries stock management
Provedor de dados: 5
Autores: Augustin, Nicole H.; Trenkel, Verena; Wood, Simon; Lorance, Pascal.
Fishery catch data offer a rich potential source of information for management, if modelling can separate out the effects of fishing effort, species behaviour and population abundance. Here, we model catch data from the blue ling fishery off the northwest coast of Scotland, using generalised additive mixed models with a space time interaction represented via a novel tensor product of a soap film smooth of space with a penalized regression spline of time. The use of soap film smoothers avoids imposing correspondences between spatially adjacent areas that are in fact separated by the stock boundary. The comparison of the performance of the soap film smooth for space–time with that of a thin plate regression spline based on root mean squared prediction errors...
Tipo: Text
Palavras-chave: GAMM; Finite area smoothing; Tensor product smooth; Space-time interaction; Tweedie distribution; Molvadypterygia.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00117/22795/20616.pdf

Interannual variability of fisheries economic returns and energy ratios is mostly explained by gear type
Provedor de dados: 5
Autores: Trenkel, Verena; Daures, Fabienne; Rochet, Marie-joelle; Lorance, Pascal.
According to portfolio theory applied to fisheries management, economic returns are stabilised by harvesting in a portfolio stocks of species whose returns are negatively correlated and for which the portfolio economic return variance is smaller than the sum of stock specific return variances. Also, variability is expected to decrease with portfolio width. Using a range of indicators, these predictions were tested for the French fishing fleets in the Bay of Biscay (Northeast Atlantic) during the period 2001–2009. For this, vessels were grouped into eight fishing fleets based on the gears used and exploited species were grouped into five functional groups. The portfolio width of fleets ranged from 1–3 functional groups, or 4–19 species. Economic fleet...
Tipo: Text
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00157/26808/24916.pdf

The relative importance of environmental stochasticity, interspecific interactions, and observation error: Insights from sardine and anchovy landings
Provedor de dados: 5
Autores: 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

Rapport sur l'utilisation du sondeur multifaisceaux ME70 lors des campagnes Pelgas08 et Class08
Provedor de dados: 5
Autores: Doray, Mathieu; Petitgas, Pierre; Masse, Jacques; Trenkel, Verena.
Report on Simrad ME70 multibeam echosounder operations during Pelgas08 and Class08 sea surveys. First observations of small pelagic fish 3D aggregative structures
Tipo: Text
Palavras-chave: Pelagic ecosystem; Bay of Biscay; 3D fisheries acoustics; Multibeam echosounder; Écosystème pélagique; Golfe de Gascogne; Acoustique halieutique 3D; Sondeur multifaisceaux.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/rapport-6314.pdf

Variability in natural behaviour, and observed reactions to an ROV, by mid-slope fish species
Provedor de dados: 5
Autores: Lorance, Pascal; Trenkel, Verena.
The behaviour of eight large benthopelagic fish taxa was analysed using video records collected with an ROV on the mid-slope of the Bay of Biscay. The studied species were roundnose grenadier (Coryphaenoides rupestris), orange roughy (Hoplostethus atlanticus), deep-sea scorpionfish (Trachyscorpia cristulata echinata), and black scabbardfish (Aphanopus carbo), as well as individuals belonging to the families Alepocephalidae, Chimaeridae, and Scyliorhinidae, and to the order Squaliformes. Some of the observed fish were grouped at the family taxonomical level due to visual identification to species being unreliable. Assumed natural (undisturbed) behaviour was categorised in terms of (i) body position with respect to the bottom sea floor, (ii) locomotion and...
Tipo: Text
Palavras-chave: ROV; Life strategies; Fish; Diversity; Continental slope; Behaviour; Bay of Biscay.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/publication-1228.pdf

Standardizing blue ling landings per unit effort from industry haul-by-haul data using generalized additive models
Provedor de dados: 5
Autores: Lorance, Pascal; Pawlowski, Lionel; Trenkel, Verena.
Haul-by-haul data derived from skippers' personal logbooks, from the French deep-water fishery to the west of the British Isles, were used to calculate standardized blue ling (Molva dypterygia) landings per unit effort (lpue) for the period 2000-2008. Lpue values were estimated using generalized additive models with depth, vessel, statistical rectangle, area, and year as explanatory variables. Because of their statistical distribution, landings were modelled by a Tweedie distribution, which allows datasets to contain many zeros. To investigate how to track stock trends reliably, lpue values were estimated in five areas for different subsets of the data. The subsets consisted of hauls during the spawning season (when blue ling aggregate), outside the...
Tipo: Text
Palavras-chave: Abundance indices; Fishing strategy; GAM; Molva dypterygia; Tallybook.
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00016/12713/9647.pdf

Impacts de l’extraction sélective d’espèces sur les populations, les communautés et les réseaux trophiques. Sous-région marine Manche - mer du Nord. Evaluation initiale DCSMM.
Provedor de dados: 5
Autores: Trenkel, Verena.
Tipo: Text
Palavras-chave: Manche; Mer du Nord; Extraction sélective; Espèces; Impacts; Populations; Communautés; Réseau trophique.
Ano: 2012
URL: https://archimer.ifremer.fr/doc/00328/43881/43455.pdf

A method for reducing uncertainty in estimates of fish-school frequency response using data from multifrequency and multibeam echosounders
Provedor de dados: 5
Autores: 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

Identifying blue whiting (Micromesistius poutassou) stock structure in the Northeast Atlantic by otolith shape analysis
Provedor de dados: 5
Autores: Mahe, Kelig; Oudard, Clemence; Mille, Tiphaine; Keating, James P; Gonçalves, Patricia; Clausen, Lotte Worsøe; Petursdottir, G; Rasmussen, H; Meland, E; Mullins, E; Pinnegar, Jk; Hoines, A; Trenkel, Verena.
Information on stock identification and spatial stock structure provide a basis for understanding fish population dynamics and improving fisheries management. In this study otolith shape analysis was used to study the stock structure of blue whiting (Micromesistius poutassou) in the northeast Atlantic using 1693 samples from mature fish collected between 37°N and 75°N and 20°W and 25°E. The results indicated two stocks located north and south of ICES Divisions VIa and VIb (54°5 to 60°5 N, 4° to 11°W). The central area corresponds to the spawning area west of Scotland. Sampling year effects and misclassification in the linear discriminant analysis suggested exchanges between the northern and southern stocks. The results corroborate previous studies...
Tipo: Text
Palavras-chave: Micromesistius poutassou; Forme de l’otolithe; Descripteurs de Fourier; Discrimination de stock; Nord-est de l’Océan atlantique.; Micromesistius poutassou; Otolith shape; Fourier descriptors; Stock discrimination; Northeast atlantic.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00334/44508/44202.pdf

Do survey design and wind conditions influence survey indices ?
Provedor de dados: 5
Autores: Poulard, Jean-charles; Trenkel, Verena.
Survey indices play an important role in stock assessments as they provide information on stock trends. In certain cases large interannual variations have been observed which are unlikely to reflect true underlying stock changes but are rather outliers. When survey indices for several species appear to be outliers for the same year, the suspicion is raised that something happened during the survey of that year. This is called a year-effect in survey catches. To study the potential year-effect in survey catches for the French autumn groundfish survey taking place in the Bay of Biscay, several indicators for survey design and wind conditions were derived as explanatory variables and Principal Component Analysis was used to study the relationship between...
Tipo: Text
Palavras-chave: Bay of Biscay; Survey conditions; Time trends; Catchability; Survey index.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/publication-2690.pdf

A framework for qualitatively evaluating management plans in a results-based perspective
Provedor de dados: 5
Autores: Rochet, Marie-joelle; Trenkel, Verena; Rice, Jake.
Currently many multi-year management plans are being developed either for rebuilding depleted stocks or for avoiding difficult negotiations when management decisions must be revisited on a regular basis. Management plans are commonly evaluated by intensive model simulations that describe the ecological and economic dynamics, and the management loop. Under the results-based management paradigm, the fishing industry or particular fishing sectors will develop their own management plans, potentially leading to a huge number of plans to be evaluated. Guidelines for evaluating the plans on a qualitative level before launching quantitative evaluations will be essential. Here we propose a framework for evaluating management strategies in a qualitative way. A...
Tipo: Text
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00029/13988/11166.pdf

Using cognitive maps to investigate fishers' ecosystem objectives and knowledge
Provedor de dados: 5
Autores: Prigent, Magali; Fontenelle, Guy; Rochet, Marie-joelle; Trenkel, Verena.
This paper presents a survey of French Eastern English Channel fishers' observations of the past and current state of the marine ecosystem and their wishes for the future, as a first step towards formulating management objectives. Twenty-nine semi-directive interviews were carried out in June 2006 among fishers and shellfish farmers. Cognitive maps proved useful to formalise their experience and knowledge. Most interviewees mentioned a decrease of the resource in recent years and pointed out the presence of several problems, such as pollution, degradation of the ocean floor and harmful impacts of human activities, including fishing. The indicators used by the fishers as the basis to form their opinion were similar to those generally used by scientists for...
Tipo: Text
Palavras-chave: Eastern English Channel; Management objectives; Stakeholder interview; Cognitive map; Ecosystem approach to fisheries; Fisher knowledge.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-6134.pdf

A random effects population dynamics model based on proportions-at-age and removal data for estimating total mortality
Provedor de dados: 5
Autores: Trenkel, Verena; Bravington, Mark V.; Lorance, Pascal.
Catch curves are widely used to estimate total mortality for exploited marine populations. The usual population dynamics model assumes constant recruitment across years and constant total mortality. We extend this to include annual recruitment and annual total mortality. Recruitment is treated as an uncorrelated random effect, while total mortality is modelled by a random walk. Data requirements are minimal as only proportions-at-age and total catches are needed. We obtain the effective sample size for aggregated proportion-at-age data based on fitting Dirichlet-multinomial distributions to the raw sampling data. Parameter estimation is carried out by approximate likelihood. We use simulations to study parameter estimability and estimation bias of four...
Tipo: Text
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00130/24168/22506.pdf

A future for marine fisheries in Europe (Manifesto of the Association Francaise d'Halieumetrie)
Provedor de dados: 5
Autores: 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

Towards an ecosystem approach to fisheries management (EAFM) when trawl surveys provide the main source of information
Provedor de dados: 5
Autores: Cotter, John; Petitgas, Pierre; Abella, Alvaro; Apostolaki, Panayiota; Mesnil, Benoit; Politou, Chrissi-yianna; Rivoirard, Jacques; Rochet, Marie-joelle; Spedicato, Maria Teresa; Trenkel, Verena; Woillez, Mathieu.
Ideas and considerations are put forward for managing fisheries and marine populations using primarily trawl surveys to supply biological and spatial indicators of the state of stocks, and to permit catch per unit effort (CPUE)-based assessments. Trawl surveys seldom allow absolute estimates of fish population sizes but, if appropriately located, timed, and designed, can provide a broad range of information about catchable fish species and the ecosystem that supports them. This information may be more conducive to sustainable management of fisheries than the traditional focus on the abundances of selected stocks. The paper first briefly proposes how survey-based methods might supplement existing fishery-dependent stock assessments, as would be necessary...
Tipo: Text
Palavras-chave: Fishing effort indicator; Fisheries independent assessment; Survey based stock assessment; Spatial indicator; State indicator; Trawl survey; Fisheries management.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6691.pdf

Functional group based marine ecosystem assessment for the Bay of Biscay via elasticity analysis
Provedor de dados: 5
Autores: 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

A review of fishery-independent assessment models, and initial evaluation based on simulated data
Provedor de dados: 5
Autores: Mesnil, Benoit; Cotter, John; Fryer, Rob J.; Needle, Coby L.; Trenkel, Verena.
Large uncertainties in catch data (officially-reported landings and discards) are undermining the ability of scientific organisations to provide valid management advice based on the conventional approach of analytical stock assessments. There is thus an urgent need to consider alternative tools that do not depend on long series of precise age-structured catch data. This paper presents four fishery-independent assessment models developed under the EU project FISBOAT (Fishery Independent Survey Based Operational Assessment Tools). It also reports on rudimentary tests based on simulated data, using the same data sets and protocol as an evaluation study conducted by the US National Research Council in 1997. The survey-based assessment models at hand are able...
Tipo: Text
Palavras-chave: Survey indices; Fishery independent assessment methods (F I methods); Catch free models; Fish stock assessment.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6902.pdf

Fish stock assessments using surveys and indicators
Provedor de dados: 5
Autores: Petitgas, Pierre; Cotter, John; Trenkel, Verena; Mesnil, Benoit.
Tipo: Text
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6686.pdf

Resolution of biodiversity and assemblage structure in demersal fisheries surveys: the role of tow duration
Provedor de dados: 5
Autores: 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

Effects of Ignoring Survey Design Information for Data Reuse
Provedor de dados: 5
Autores: 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

Do changes in environmental and fishing pressures impact marine communities? An empirical assessment
Provedor de dados: 5
Autores: 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&gt;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

A framework for evaluating management plans comprehensively
Provedor de dados: 5
Autores: Trenkel, Verena; Rochet, Marie-joelle; Rice, Jake C.
We present a framework for evaluating fisheries management plans comprehensively, both rebuilding plans and others. The framework includes a first rapid appraisal of the likelihood that the plan will result in management meeting its objectives, and guides subsequent quantitative analyses of potential weaknesses in the proposed plan. The framework includes four steps: (i) evaluating if a set of management objectives, if achieved, would result in a sustainable fishery, (ii) using qualitative analysis of a bio-economic model to evaluate whether the set of stock management tactics might be capable of achieving the specified fisheries objectives, (iii) using empirical criteria derived from the literature to evaluate if other management measures in the plan...
Tipo: Text
Palavras-chave: Loop analysis; Management strategy; Management strategy evaluation; Qualitative modelling; Stock rebuilding; Sustainability.
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00198/30931/29363.pdf

A new class of predator prey models with interactions described by thresholds
Provedor de dados: 5
Autores: 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

A certain stability in topics and a highly connected community. Text mining of acoustic symposia abstracts
Provedor de dados: 5
Autores: 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
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00598/71042/69352.pdf

Determining long-term changes in a skate assemblage with aggregated landings and limited species data
Provedor de dados: 5
Autores: 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
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00470/58214/60718.pdf

A new compilation of stomach content data for commercially-important pelagic fish species in the Northeast Atlantic
Provedor de dados: 5
Autores: Pinnegar, J. K.; Goni, N.; Trenkel, Verena; Arrizabalaga, H.; Melle, W.; Keating, J.; Oskarsson, G.
There is increasing demand for information on predator-prey interactions in the ocean as a result of legislative commitments aimed at achieving sustainable exploitation. However, comprehensive datasets are lacking for many fish species and this has hampered development of multispecies fisheries models and the formulation of effective food-web indicators. This work describes a new compilation of stomach content data for five pelagic fish species (herring, blue whiting, mackerel, albacore and bluefin tuna) sampled across the northeast Atlantic and submitted to the PANGAEA open-access data portal (www.pangaea.de). We provide detailed descriptions of sample origin and of the corresponding database structures. We describe the main results in terms of diet...
Tipo: Text
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00195/30641/29096.pdf

Estimating effective population size using RADseq: Effects of SNP selection and sample size
Provedor de dados: 5
Autores: 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

Estimating the economic loss of recent North Atlantic fisheries management
Provedor de dados: 5
Autores: 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
Ano: 2014
URL: https://archimer.ifremer.fr/doc/00188/29973/28426.pdf

Estimation des rejets de peche des chalutiers français en mer Celtique
Provedor de dados: 5
Autores: Rochet, Marie-joelle; Trenkel, Verena; Peronnet, Isabelle.
Discards of the French trawler fleet operating in the Celtic Sea in 1997 were studied. Twenty-six trips, representing 0.8% of the total fishing effort, were sampled. This fleet consists of three métiers, benthic trawlers, demersal trawlers and Nephrops trawlers. The fleet discarded an estimated 30,000 tons of animals in 1997, while landing 63,000 tons. The total quantity discarded did not differ among métiers, but the species composition of discards did. Benthic trawlers discarded mainly by-catch species, whereas demersal and Nephrops trawlers discarded primarily their target species. Whiting, megrim, Nephrops and hake were discarded in larger numbers than landed. Hence discards should probably be taken into account in catch-based assessments. However,...
Tipo: Text
Palavras-chave: Espèce non commerciale; Langoustine; Baudroie; Poisson plat; Gadidé; Mer celtique; Echantillonnage des rejets; Non commercial species; Nephrop; Anglerfish; Flatfish; Gadoid; Trawler; Celtic Sea; Discard sampling.
Ano: 2001
URL: https://archimer.ifremer.fr/doc/2001/rapport-1575.pdf

Impacts de l’extraction sélective d’espèces sur les populations, les communautés et les réseaux trophiques. Sous-région marine Golfe de Gascogne. Evaluation initiale DCSMM.
Provedor de dados: 5
Autores: Trenkel, Verena.
Tipo: Text
Palavras-chave: Golfe de Gascogne; Extraction sélective; Espèces; Impacts; Populations; Communautés; Réseau trophique.
Ano: 2012
URL: https://archimer.ifremer.fr/doc/00329/44068/43639.pdf

Interpretation of interannual variability in long-term aquatic ecological surveys
Provedor de dados: 5
Autores: Cauvy-fraunié, Sophie; Trenkel, Verena; Daufresne, Martin; Maire, Anthony; Capra, Hervé; Olivier, Jean-michel; Lobry, Jérémy; Cazelles, Bernard; Lamouroux, Nicolas.
Long-term ecological surveys (LTES) often exhibit strong variability among sampling dates. The use and interpretation of such interannual variability is challenging due to the combination of multiple processes involved and sampling uncertainty. Here, we analysed the interannual variability in ~30 years of 150 species-density (fish and invertebrate) and environmental-observation time series in four aquatic-systems (stream, river, estuary, and marine continental shelf) with different sampling efforts to identify the information provided by this variability. We tested, using two empirical methods, whether we could observe simultaneous fluctuation between detrended time series corresponding to widely acknowledged assumptions about aquatic population dynamics:...
Tipo: Text
Palavras-chave: Long-term ecological surveys (LTES); Aquatic species (stream -river-estuary- marine); Interannual variability; Symbolic analyses; Sampling efficiency.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00606/71805/70293.pdf

L'état des communautés exploitées au large des côtes de France. Application d'indicateurs à l'évaluation de l'impact de la pêche. Bilan 2004 – Edition 2009
Provedor de dados: 5
Autores: Morin, Jocelyne; Bertrand, Jacques; Cochard, Marie-laure; Coppin, Franck; Leaute, Jean-pierre; Lobry, Jeremy; Mahe, Jean-claude; Poulard, Jean-charles; Rochet, Marie-joelle; Schlaich, Ivan; Souplet, Arnauld; Trenkel, Verena; Vaz, Sandrine; Verin, Yves.
Since about twenty years, Ifremer have carried out fishery surveys along the French coasts. A dynamic indicator-based approach to the assessment of multi-stock fisheries has been applied to these data series. Reference points for non-commercial populations and community indicators are seldom available, but reference directions are well established: it is known whether fishing will increase or decrease the indicator, hence the direction that should be avoided. A set of simple indicators of fishing impacts on fish populations and communities were estimated from time-series data provided by scientific surveys (population abundance and average length, community total biomass and number, average length and weight, and size spectrum). Trends in these indicators...
Tipo: Text
Palavras-chave: Communauté; Population; Indicateurs; Campagnes scientifiques; Pêcheries multi spécifiques; Approche écosystémique pour la gestion des pêches.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/rapport-7293.pdf

Estimating effective population size of large marine populations, is it feasible?
Provedor de dados: 5
Autores: Marandel, Florianne; Lorance, Pascal; Berthele, Olivier; Trenkel, Verena; Waples, Robin S.; Lamy, Jean-baptiste.
stainable exploitation of marine populations is a challenging task relying on information about their current and past abundance. Fisheries‐related data can be scarce and unreliable making them unsuitable for quantitative modelling. One fishery independent method that has attracted attention in this context consists in estimating the effective population size (Ne), a concept founded in population genetics. We reviewed recent empirical studies on Ne and carried out a simulation study to evaluate the feasibility of estimating Ne in large fish populations with the currently available methods. The detailed review of 26 studies found that published empirical Ne values were very similar despite differences in species and total population sizes (N). Genetic...
Tipo: Text
Palavras-chave: Census population size; Effective population size; Fish; Linkage disequilibrium; Management; Simulation.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00470/58162/60678.pdf

Combining indicator trends to assess ongoing changes in exploited fish communities: diagnostic of communities off the coasts of France
Provedor de dados: 5
Autores: Rochet, Marie-joelle; Trenkel, Verena; Bellail, Robert; Coppin, Franck; Le Pape, Olivier; Mahe, Jean-claude; Morin, Jocelyne; Poulard, Jean-charles; Schlaich, Ivan; Souplet, Arnauld; Verin, Yves; Bertrand, Jacques.
We present a method for combining individual indicator results into a comprehensive diagnostic of fishing impacts on fish populations and communities. A conceptual framework for interpreting combined trends in a set of simple indicators is proposed, relying beforehand on qualitative expectations anchored in ecological theory. The initial state of the community is first assessed using published information. Which combinations of trends are acceptable or undesirable is decided, depending on the initial status. The indicators are then calculated from a time-series and their time trends are estimated as the slopes of linear models. Finally, the test results are combined within the predefined framework, providing a diagnostic on the dynamics of fishing impacts...
Tipo: Text
Palavras-chave: Scientific surveys; Multispecies fisheries; Indicators; Ecosystem approach to fisheries management.
Ano: 2005
URL: http://archimer.ifremer.fr/doc/2005/publication-773.pdf

Analysis of species associations in deep-sea fisheries off the British Isles from an industry haul-by-haul database
Provedor de dados: 5
Autores: Baulier, Loic; Pawlowski, Lionel; Lorance, Pascal; Trenkel, Verena.
Tipo: Text
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00018/12951/9926.pdf

We can reduce the impact of scientific trawling on marine ecosystems
Provedor de dados: 5
Autores: Trenkel, Verena; Vaz, Sandrine; Albouy, Camille; Brind'Amour, Anik; Duhamel, Erwan; Laffargue, Pascal; Romagnan, Jean-baptiste; Simon, Julien; Lorance, Pascal.
The negative impacts that scientific monitoring may have on marine ecosystems has been a neglected topic, mainly on the basis that its magnitude is minor compared to commercial fisheries, even though this raises ethical and, in certain cases, conservation issues. We argue that ethical principles should lead us to reconsider marine wildlife resource monitoring such as the fish and shellfish trawl surveys providing the science-based evidence needed for fisheries management and assessment of how environmental change impacts marine shelf communities worldwide. Recent scientific and technological progress has provided methods and tools which might now be harnessed to reduce the impact of marine monitoring. We review these alternative methods, consider...
Tipo: Text
Palavras-chave: Monitoring ethics; Marine surveying; Impacts of bottom trawling; Genetic methods; Ecosystem-based management.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00470/58161/60665.pdf

Hake catchability by the French trawler fleet in the Bay of Biscay: estimating technical and biological components
Provedor de dados: 5
Autores: 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

Cluster analysis of linear model coefficients under contiguity constraints for identifying spatial and temporal fishing effort patterns
Provedor de dados: 5
Autores: Mahevas, Stephanie; Bellanger, Lise; Trenkel, Verena.
For fisheries management purposes, it is essential to take into account spatial and seasonal characteristics of fishing activities to allow a reliable assessment of fishing impact on resource. This paper presents a novel technique for describing spatial and temporal patterns in fishing effort. The spatial and seasonal fishing activity patterns of the French trawler fleet in the Celtic Sea during the period 1991–1998 were analysed by modelling fishing effort (fishing time) with generalised linear models. The linear model for fishing effort included fixed effects for both spatial (statistical rectangles) and temporal units (months). In addition, spatial correlations in any given month were modelled by an exponentially decreasing function. Temporal...
Tipo: Text
Palavras-chave: Fleet dynamics; Allocation of Fishing effort; Spatial and seasonal pattern; Statistics for spatial data; Cluster analysis under contiguity constraints; Generalised linear model.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-4302.pdf

Disentangling the effects of capture efficiency and population abundance on catch data using random effects models
Provedor de dados: 5
Autores: 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

Statistical ecology comes of age
Provedor de dados: 5
Autores: 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

Determining long‐term changes in a skate assemblage with aggregated landings and limited species data
Provedor de dados: 5
Autores: Marandel, Florianne; Lorance, Pascal; Trenkel, Verena.
Sustainable fisheries management requires assessment of exploited populations and communities. Traditional fisheries stock assessment methods need species‐specific input data, which for skates have only recently become available in Europe. To overcome this limitation, a Bayesian multispecies biomass production model was developed. In addition to aggregated landings, input data are short time series with species‐specific information (landings and biomass indices). Applying the approach to four main skate species and a group of two skate species, all managed together in the Bay of Biscay (Northeast Atlantic), long‐term changes in the skate assemblage composition were identified. Since the 1990s, Leucoraja naevus became increasingly dominant, while the...
Tipo: Text
Palavras-chave: Community changes; Fishing impacts; Multispecies management; Multispecies model; Rajiformes; Species composition; Vulnerable skates.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00589/70088/68138.pdf

Using qualitative and quantitative stakeholder knowledge: examples from European deep-water fisheries
Provedor de dados: 5
Autores: 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

A fisheries acoustic multi-frequency indicator to inform on large scale spatial patterns of aquatic pelagic ecosystems
Provedor de dados: 5
Autores: 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

Does diet in Celtic Sea fishes reflect prey availability?
Provedor de dados: 5
Autores: 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

Do population and community metrics tell the same story about recent changes in Northern Mediterranean fish communities?
Provedor de dados: 5
Autores: Rochet, Marie-joelle; Trenkel, Verena; Gil De Sola, Luis; Politou, Chrissi-yianna; Tserpes, George; Bertrand, Jacques.
This document presents a comparative study of human impacts on the length-structure of fish communities across North-Mediterranean ecosystems. We use survey data to examine trends in length-based metrics and their consistency within and among the two levels of organisation populations and communities, and to suggest interpretations of observed trend combinations. We start from a set of population processes potentially affected by human pressures: fishing will induce mortality especially in target species, whereas the hydrological environment and eutrophication potentially affect recruitment and individual growth. How population changes will be reflected at the community level is expected to depend on community evenness. Based on this expectation, a...
Tipo: Text
Palavras-chave: Community metrics; Ecosystem approach to fisheries; Fish community; Length-based metrics; Mediterranean; Survey data.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/00133/24377/22389.pdf

Rapport sur l'utilisation du sondeur multifaisceaux ME70 lors de la campagne Pelgas09
Provedor de dados: 5
Autores: Doray, Mathieu; Masse, Jacques; Petitgas, Pierre; Trenkel, Verena.
Le sondeur multifaisceaux Simrad ME70 (ou SMFH) (Trenkel et al., 2008) a été utilisé pour la première fois en routine en parallèle des sondeurs monofaisceaux ER60 lors de la campagne Pelgas09 (25/04-05/06/2009).  Le premier objectif était de tester la faisabilité d'une utilisation en routine du ME70 lors d'une campagne visant à évaluer par acoustique les stocks d'anchois et de sardine du Golfe de Gascogne.  A terme, les données récoltées lors de cette campagne permettront d'étudier l'apport du sondeur multifaisceaux ME70 à l'estimation de biomasse, en comparant les estimations de stocks obtenues en mono et multifaisceaux.  Les données acoustiques 3D collectées au moyen du ME70 dans l'ensemble du Golfe de Gascogne lors de Pelgas09 doivent également...
Tipo: Text
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/rapport-6755.pdf

Poissons et invertébrés au large des côtes de France : Indicateurs issus des pêches scientifiques. Bilan 2002
Provedor de dados: 5
Autores: 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

Intersection-union tests for characterising recent changes in smoothed indicator time series
Provedor de dados: 5
Autores: 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

Small-scale spatial and temporal interactions among benthic crustaceans and one fish species in the Bay of Biscay
Provedor de dados: 5
Autores: Trenkel, Verena; Le Loch, Francois; Rochet, Marie-joelle.
In the summer of 2004, a video survey was carried out in the northern part of the central mud bank (Grande Vasiere) of the Bay of Biscay to study the small scale relationship between the dominant crustacean megafauna Nephrops norvegicus, Munida rugosa and Goneplax rhomboides and juvenile hake (Merluccius merluccius). Using a towed body, high-resolution videos were recorded in six sampling sites. Statistical modelling using generalised additive models (GAM) revealed variations in activity patterns for two species. More N. norvegicus were observed outside their burrows at dawn and somewhat at dusk (no observations during night) while G. rhomboides was less observed in the morning. In addition, reduced spatial overlap between G. rhomboides and N. norvegicus...
Tipo: Text
Palavras-chave: Competition; Variations in activity patterns; Video; Benthos.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/publication-2614.pdf