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  • 11
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    Online Resource
    Combining quantitative and qualitative models to identify functional groups for monitoring changes in the Bay of Biscay continental shelf exploited foodweb
    Oxford University Press (OUP) ; 2014
    In:  ICES Journal of Marine Science Vol. 71, No. 1 ( 2014-01-01), p. 105-117
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 71, No. 1 ( 2014-01-01), p. 105-117
    Abstract: Lassalle, G., Nelva Pasqual, J-S., Boët, P., Rochet, M-J., Trenkel, V. M., and Niquil, N. Combining quantitative and qualitative models to identify functional groups for monitoring changes in the Bay of Biscay continental shelf exploited foodweb. – ICES Journal of Marine Science, 71: . 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 identified as a sensitive and robust indicator for monitoring foodweb ecological status in the Bay of Biscay. The present study also suggested the potential antagonistic effects of alternative management measures on small pelagic fish and highlighted the need for the joint management of all pressures.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fst107
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2014
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  • 12
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    Different surveys provide similar pictures of trends in a marine fish community but not of individual fish populations
    Oxford University Press (OUP) ; 2004
    In:  ICES Journal of Marine Science Vol. 61, No. 3 ( 2004-01-01), p. 351-362
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 61, No. 3 ( 2004-01-01), p. 351-362
    Abstract: 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 as proportions of non-commercial and piscivorous species, and the proportion of benthic species showed similar trends for all data series. The shape of the size spectrum based on abundances per length class summed over all fish species, although stable over time, was highly sensitive to the sampling method. With the exception of size spectra, community indicators for marine fish assemblages monitored by surveys seem to be robust to survey period and trawling gear, but species abundance trends are method dependent.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1016/j.icesjms.2004.01.004
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2004
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  • 13
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    From model-based prescriptive advice to indicator-based interactive advice
    Oxford University Press (OUP) ; 2007
    In:  ICES Journal of Marine Science Vol. 64, No. 4 ( 2007-05-01), p. 768-774
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 64, No. 4 ( 2007-05-01), p. 768-774
    Abstract: Trenkel, V. M., Rochet, M-J., and Mesnil, B. 2007. From model-based prescriptive advice to indicator-based interactive advice. – ICES Journal of Marine Science, 64: 768–774. 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 available information. Changes in indicator values after this reference time are then estimated, interpreted, and finally combined into a diagnostic that highlights possible causes of the changes observed. After considering management objectives, appropriate management actions can then be proposed. The proposed approach is illustrated for anglerfish stocks in the Celtic Sea and the Bay of Biscay.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsm006
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2007
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  • 14
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    The new fisheries multibeam echosounder ME70: description and expected contribution to fisheries research
    Oxford University Press (OUP) ; 2008
    In:  ICES Journal of Marine Science Vol. 65, No. 4 ( 2008-05-01), p. 645-655
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 65, No. 4 ( 2008-05-01), p. 645-655
    Abstract: Trenkel, V. M., Mazauric, V., and Berger, L. 2008. The new fisheries multibeam echosounder ME70: description and expected contribution to fisheries research. – ICES Journal of Marine Science, 65: 645–655. 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 70–120 kHz, spanning at most 150°. All beams are stabilized in vessel roll and pitch. It has reduced side-lobe levels, up to −70 dB (two-way) instead of the −25 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 developments using the new system are outlined.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsn051
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2008
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  • 15
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    Ecosystem trends: evidence for agreement between fishers' perceptions and scientific information
    Oxford University Press (OUP) ; 2008
    In:  ICES Journal of Marine Science Vol. 65, No. 6 ( 2008-09-01), p. 1057-1068
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 65, No. 6 ( 2008-09-01), p. 1057-1068
    Abstract: Rochet, M-J., Prigent, M., Bertrand, J. A., Carpentier, A., Coppin, F., Delpech, J-P., Fontenelle, G., Foucher, E., Mahé, K., Rostiaux, E., and Trenkel, V. M. 2008. Ecosystem trends: evidence for agreement between fishers' perceptions and scientific information. – ICES Journal of Marine Science, 65: 1057–1068. 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. They had a greater power than survey data to detect recent changes, showing that fishers' perceptions have great potential as early warning signals.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsn062
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2008
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  • 16
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    Hake catchability by the French trawler fleet in the Bay of Biscay: estimating technical and biological components
    Oxford University Press (OUP) ; 2011
    In:  ICES Journal of Marine Science Vol. 68, No. 1 ( 2011-01-01), p. 107-118
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 68, No. 1 ( 2011-01-01), p. 107-118
    Abstract: Mahévas, S., Trenkel, V. M., Doray, M., and Peyronnet, A. 2011. Hake catchability by the French trawler fleet in the Bay of Biscay: estimating technical and biological components. – ICES Journal of Marine Science, 68: 107–118. 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 trawlers of the French trawler fleet were used. Daytime accessibility to large hake was lower than at night, and about zero for small hake ( 〈 19 cm). Estimates of spatial variation made using generalized linear mixed models showed a patchy fine-scale spatial distribution, but a random larger-scale distribution of hake over the area surveyed.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsq140
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2011
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  • 17
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    Observing the ocean interior in support of integrated management
    Oxford University Press (OUP) ; 2016
    In:  ICES Journal of Marine Science Vol. 73, No. 8 ( 2016-09-01), p. 1947-1954
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 73, No. 8 ( 2016-09-01), p. 1947-1954
    Abstract: 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 ecological questions and the increasing move towards ecosystem based management pose further challenges to scientists and instrument developers. Considering the SoME Acoustics presentations in the context of three previous ICES symposia on fisheries acoustics, topics increasingly emphasize ecosystem studies and management. The continued expansion of work and progress in marine ecosystem acoustics is due to the cross-disciplinary work of fisheries acousticians, engineers, ecologists, modellers, and others. An analysis of the symposium co-authorship network reveals a highly connected acoustic science community collaborating around the globe.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsw132
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2016
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  • 18
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    Estimating end effects in trawl catches
    Oxford University Press (OUP) ; 2006
    In:  ICES Journal of Marine Science Vol. 63, No. 5 ( 2006-01-01), p. 956-959
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 63, No. 5 ( 2006-01-01), p. 956-959
    Abstract: 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 consequence, the bias in abundance indices derived from swept area estimates that ignore end effects will be species-dependent.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1016/j.icesjms.2006.03.002
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2006
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  • 19
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    A method for reducing uncertainty in estimates of fish-school frequency response using data from multifrequency and multibeam echosounders
    Oxford University Press (OUP) ; 2009
    In:  ICES Journal of Marine Science Vol. 66, No. 6 ( 2009-07-01), p. 1155-1161
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 66, No. 6 ( 2009-07-01), p. 1155-1161
    Abstract: Berger, L., Poncelet, C., and Trenkel, V. M. 2009. A method for reducing uncertainty in estimates of fish-school frequency response using data from multifrequency and multibeam echosounders. – ICES Journal of Marine Science, 66: 1155–1161. 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 imaged with the multibeam echosounder. Echoes that exceed the overlap threshold are used to estimate the r(f). The proposed method is applied to simulated and actual data for sardine and mackerel schools in the Bay of Biscay to estimate their r(f) values. The results for different overlap thresholds are compared with the results of a different method, one that uses adaptive thresholds on volume-backscattering strength Sv. The proposed method reduces uncertainty in estimates of r(f) for schools with an overlap of greater than 80%, and it outperforms the Sv-thresholding technique.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsp113
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2009
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  • 20
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    Standardizing blue ling landings per unit effort from industry haul-by-haul data using generalized additive models
    Oxford University Press (OUP) ; 2010
    In:  ICES Journal of Marine Science Vol. 67, No. 8 ( 2010-11-01), p. 1650-1658
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 67, No. 8 ( 2010-11-01), p. 1650-1658
    Abstract: Lorance, P., Pawlowski, L., and Trenkel, V. M. 2010. Standardizing blue ling landings per unit effort from industry haul-by-haul data using generalized additive models. – ICES Journal of Marine Science, 67: 1650–1658. 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 spawning season, and hauls in which blue ling was only a bycatch. The results suggest that blue ling lpue values have been stable over the period 2000–2008, and that the declining trend previously observed for the stock has been halted. This finding is consistent with stable mean lengths in the landings during the same period. The study demonstrates the greater suitability of haul-by-haul data than EC logbook data for deriving abundance indices for deep-water stocks.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsq048
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2010
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