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  • 1
    Online Resource
    Online Resource
    Modelling the variability in fish spatial distributions over time with empirical orthogonal functions: anchovy in the Bay of Biscay
    Oxford University Press (OUP) ; 2014
    In:  ICES Journal of Marine Science Vol. 71, No. 9 ( 2014-11-01), p. 2379-2389
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 71, No. 9 ( 2014-11-01), p. 2379-2389
    Abstract: Characterizing the space–time variability in spatial distributions as well as understanding its drivers is basic to designing robust spatial management plans. As a prerequisite, we analyse here how this variability relates to population dynamics in conjunction with environmental conditions. For that, spatio-temporal statistical approaches are needed but seldom used in fisheries science. To fill this gap, we showcase the usefulness of the method of empirical orthogonal functions (EOFs). Guidelines are given to apply the method on a series of gridded maps as derived from fisheries survey dataseries that now span over decades. The method is applied to the series, 2000–2012, of the spatial distributions of European anchovy in the Bay of Biscay at spawning time. Across the series, the EOF decomposition allowed to identify three main types of spatial distributions. One type corresponded to an extended distribution, another to a restricted distribution in core areas, and the third to a very coastal distribution. The coastal spawning distribution corresponded to a low population growth rate as it was never followed by a large recruitment in the subsequent year. We did not attempt to explain the spatial patterns per se but the drivers of change from one type of distribution to another. Stock size and fish size as well as bottom temperature and water column stratification were the covariates that controlled the variability in the spatial distributions over time. Further, the spatial distribution at spawning time related to recruitment in the following year, meaning that variability in the spatial distribution of spawning affected population dynamics. The typology of maps based on EOF decomposition summarized this spatial variability into spatial spawning configurations, which may serve spatial planning.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    URL: Article
    DOI: 10.1093/icesjms/fsu111
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2014
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  • 2
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    A geostatistical method for assessing biomassof tuna aggregations around moored fish aggregating devices with star acoustic surveys
    Canadian Science Publishing ; 2008
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 65, No. 6 ( 2008-06), p. 1193-1205
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 65, No. 6 ( 2008-06), p. 1193-1205
    Abstract: Universal kriging was used to model the spatio-temporal variability in the acoustic density of tuna aggregations recorded during star echosounding surveys around moored fish aggregating devices (FADs) in Martinique (Lesser Antilles). The large-scale deterministic drift in the tuna spatial distribution was modeled using an advection–diffusion equation applied to animal grouping. Residuals from the drift were modeled as a random component with small-scale spatial correlation. An estimation variance formula was derived from this deterministic–statistical mixed model to assess the mean precision of density estimates of daytime tuna aggregation. The mean relative error obtained with our star design for daytime surveys was 24%. The methodology was applied to estimate daily maxima of tuna biomass around moored FADs during four monthly sea cruises. The daily peak of tuna biomass aggregated around moored FADs was 9 t on average (standard deviation = 4). Estimation variances for different survey designs were compared for optimizing sampling strategy.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/F08-050
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2008
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  • 3
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    Spatially explicit estimation of fish length histograms, with application to anchovy habitats in the Bay of Biscay
    Oxford University Press (OUP) ; 2011
    In:  ICES Journal of Marine Science Vol. 68, No. 10 ( 2011-11-01), p. 2086-2095
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 68, No. 10 ( 2011-11-01), p. 2086-2095
    Abstract: Petitgas, P., Doray, M., Massé, J., and Grellier, P. 2011. Spatially explicit estimation of fish length histograms, with application to anchovy habitats in the Bay of Biscay. – ICES Journal of Marine Science, 68: 2086–2095. Fish length frequency histograms from research surveys are of prime importance for identifying habitats of different life stages, as well as for stock assessment. However, no method has thus far been available for mapping these histograms as spatially varying curves. Here, a procedure is applied to map spatially connected curves, and detail is given on how it can be applied to map the length frequency histograms. At each sample location, a fish length frequency histogram is given as a vector of non-independent values. The histogram is first modelled as a polynomial expansion on the basis of orthogonal polynomials. Then, the polynomial coefficients are mapped by co-kriging, after fitting a model of co-regionalization. The length frequency map is finally derived by linearly combining maps of polynomial coefficients. An estimation variance associated with the map is also derived. Maps of anchovy length distributions are produced by applying the method to midwater trawl length data from the PELGAS acoustic surveys in the Bay of Biscay. This novel approach extends the application of kriging techniques to curves or functions, opening new perspectives for mapping more complex information than just the values of fish density.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsr139
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2011
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  • 4
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    A method for controlled target strength measurements of pelagic fish, with application to European anchovy (Engraulis encrasicolus)
    Oxford University Press (OUP) ; 2016
    In:  ICES Journal of Marine Science Vol. 73, No. 8 ( 2016-09-01), p. 1987-1997
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 73, No. 8 ( 2016-09-01), p. 1987-1997
    Abstract: Measuring fish target strength (TS) in the wild is challenging because: (i) TS varies versus physical (orientation relative to the incident sound wave, size, and depth) and physiological fish attributes (maturity and condition), (ii) the target species and its aforementioned attributes are difficult to assess in near real time, and (iii) in the case of packed fish schools, accepted echoes may originate from multiple unresolved targets. We propose a method for controlled TS measurements of densely packed small pelagic fish during daytime, based on the joint use of a Remotely Operated Towed Vehicle, “EROC”, with a pelagic trawl fitted with a codend opening system, “ENROL”. EROC, equipped with a 70-kHz split-beam echosounder (Simrad EK60) and a low-light black and white camera, can be moved inside the fishing trawl. Pelagic fish are funnelled into the open trawl and their TS is measured in the middle of the net, where small groups actively swim towards the trawl mouth. The swimming behaviour allows for near-dorsal TS to be measured, minimizing the large effect of incidence angle on TS variability. The EROC camera, located near the open codend, provides optical identification of the species. This method was used to measure the TS of European Anchovy, Engraulis encrasicolus in the Bay of Biscay during 2014. The mean, near dorsal TS was −43.3 dB, for a mean fork length of 12.5 cm. This value is compared to published values of clupeiforms mean TS obtained for a range of natural incidence angles and discussed in the light of TS modelling results obtained for E. encrasicolus.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsw084
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2016
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  • 5
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    Joint use of echosounding, fishing and video techniques to assess the structure of fish aggregations around moored Fish Aggregating Devices in Martinique (Lesser Antilles)
    EDP Sciences ; 2007
    In:  Aquatic Living Resources Vol. 20, No. 4 ( 2007-10), p. 357-366
    Details
    In: Aquatic Living Resources, EDP Sciences, Vol. 20, No. 4 ( 2007-10), p. 357-366
    Type of Medium: Online Resource
    ISSN: 0990-7440 , 1765-2952
    URL: Article
    DOI: 10.1051/alr:2008004
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2007
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  • 6
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    The influence of the environment on the variability of monthly tuna biomass around a moored, fish-aggregating device
    Oxford University Press (OUP) ; 2009
    In:  ICES Journal of Marine Science Vol. 66, No. 6 ( 2009-07-01), p. 1410-1416
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 66, No. 6 ( 2009-07-01), p. 1410-1416
    Abstract: Doray, M., Petitgas, P., Nelson, L., Mahévas, S., Josse, E., and Reynal, L. 2009. The influence of the environment on the variability of monthly tuna biomass around a moored, fish-aggregating device. – ICES Journal of Marine Science, 66: 1410–1416. Fish-aggregating devices (FADs) are increasingly used worldwide to enhance tuna catches. Meanwhile, ecosystem-based management of this fishery is constrained by a paucity of information regarding the interaction of FAD-associated tuna aggregations with their local environment. This paper reports the results of a nine-month study around a FAD moored near Martinique Island, aimed at assessing the effects of the local environment on the variability of monthly estimates of proximate tuna biomass. Dual-frequency, active acoustics provided high-resolution quantitative data on the pelagic community around the FAD, from fish to micronekton forage. Geostatistics were used to compute biomass estimates of the tuna aggregation comprising most of the FAD-associated fish biomass, with a sampling error of 27%. Environmental variability was summarized by a small set of principal components (PCs) derived from profiles of temperature, salinity, and dissolved oxygen vs. depth; and maps of chlorophyll a derived from remotely sensed, sea surface colour. A generalized linear model was used to relate tuna biomass to environmental PCs and revealed a positive correlation between tuna abundance and: (i) a micronekton layer sensed at 38 kHz and potentially consisting of preferred prey at ∼180-m depth; and (ii) low subsurface salinity (60–80 m). These favourable environmental conditions may be related to the presence of North Brazilian Current eddies that migrating tuna follow when not temporally associated with the FADs.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsp039
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2009
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  • 7
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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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  • 8
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    Estimating gear efficiency in a combined acoustic and trawl survey, with reference to the spatial distribution of demersal fish
    Oxford University Press (OUP) ; 2010
    In:  ICES Journal of Marine Science Vol. 67, No. 4 ( 2010-05-01), p. 668-676
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 67, No. 4 ( 2010-05-01), p. 668-676
    Abstract: Doray, M., Mahévas, S., and Trenkel, V. M. 2010. Estimating gear efficiency in a combined acoustic and trawl survey, with reference to the spatial distribution of demersal fish. – ICES Journal of Marine Science, 67: 668–676. 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 composition in the trawl, fish-length structure, and available relationships between target strength and fish length. Estimates of trawl efficiency for hake-dominated trawls were computed as the slopes of the relationships ENASC = 0.008 NASC and ENASC = 0.18 NASC0.31 for trawls made by day and night, respectively. For the whole demersal community, the relationships were ENASC = 0.022 NASC and ENASC = 0.17 NASC0.33 for trawls made by day and night, respectively.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsp277
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2010
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  • 9
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    Hide and seek in the Bay of Biscay—a functional investigation of marine megafauna and small pelagic fish interactions
    Oxford University Press (OUP) ; 2019
    In:  ICES Journal of Marine Science Vol. 76, No. 1 ( 2019-01-01), p. 113-123
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 76, No. 1 ( 2019-01-01), p. 113-123
    Abstract: Prey and predator distributions influence one another. Understanding the scale and the orientation of predator–prey spatial correlations is crucial in foraging ecology. Growing evidence suggests that predator–prey interactions are more constrained by functional characteristics of both the predator and the prey. Unfortunately, in marine pelagic systems, the scale and orientation of spatial correlations between predators and prey have been only little explored from a functional point of view. We tested the existence of fine-scale association between predators and fish functional groups. Visual predator sightings and acoustic fish records were collected synchronously during oceanographic surveys from 2004 to 2014. Prey biomass was integrated by nautical miles and split into four size classes ( & lt;10 cm; 10–20 cm; 20–30 cm; & gt;30 cm) and two depth layers (surface, deep). We computed the relative biomass by prey size and depth category from 0 to 12 nm around predator sightings to determine the predators’ proximity to local prey biomass. Two cetaceans (common, bottlenose dolphins) and three seabirds (northern gannets, auks, northern fulmars) were studied. No association was found in fulmars, indicating they probably do not feed on considered fishes in the area. Gannets and auks were positively correlated with local prey biomass for sizes & lt;20 cm at both depth layers. Significant negative relationships were found between common dolphins and prey size classes & lt;20 cm at both depth layers, and between bottlenose dolphins and all size ranges at the deeper layer. Our results suggest that the fine-scale spatial overlap of predator and prey is influenced by their functional traits, and that prey exhibit predator avoidance behaviour in presence of swimming predators but not of flying ones.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    URL: Article
    DOI: 10.1093/icesjms/fsy143
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2019
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  • 10
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    Overview of recent progress in fisheries acoustics made by Ifremer with examples from the Bay of Biscay
    EDP Sciences ; 2009
    In:  Aquatic Living Resources Vol. 22, No. 4 ( 2009-10), p. 433-445
    Details
    In: Aquatic Living Resources, EDP Sciences, Vol. 22, No. 4 ( 2009-10), p. 433-445
    Type of Medium: Online Resource
    ISSN: 0990-7440 , 1765-2952
    URL: Article
    DOI: 10.1051/alr/2009027
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2009
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    detail.hit.zdb_id: 291280-6
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