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  • 1
    Online Resource
    Online Resource
    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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  • 2
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    Pelagic habitat: exploring the concept of good environmental status
    Oxford University Press (OUP) ; 2017
    In:  ICES Journal of Marine Science Vol. 74, No. 9 ( 2017-12-01), p. 2333-2341
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 74, No. 9 ( 2017-12-01), p. 2333-2341
    Abstract: 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 species present under current environmental conditions should be able to find the pelagic habitats essential to close their life cycles; (ii) biogeochemical regulation is maintained at normal levels; (iii) critical physical dynamics and movements of biota and water masses at multiple scales are not obstructed. Reference points for acceptable levels of each condition and how these may change over time in line with prevailing oceanographic conditions, should be discussed by knowledge brokers, managers and stakeholders. Managers should think about a habitat hydrography rather than a habitat geography. Setting the bounds of the habitats requires a consideration of dimension, scale and gradients. It is likely that to deal with the challenges caused by a dynamic environment and the relevance of differing spatial and temporal scales, we will need to integrate multidisciplinary empirical data sets with spatial and temporal models to assess and monitor progress towards, or displacement from GES of the pelagic habitat.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    URL: Article
    DOI: 10.1093/icesjms/fsx158
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2017
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  • 3
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    Trend analysis of indicators: a comparison of recent changes in the status of marine ecosystems around the world
    Oxford University Press (OUP) ; 2010
    In:  ICES Journal of Marine Science Vol. 67, No. 4 ( 2010-05-01), p. 732-744
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 67, No. 4 ( 2010-05-01), p. 732-744
    Abstract: Blanchard, J. L., Coll, M., Trenkel, V. M., Vergnon, R., Yemane, D., Jouffre, D., Link, J. S., and Shin, Y-J. 2010. Trend analysis of indicators: a comparison of recent changes in the status of marine ecosystems around the world. – ICES Journal of Marine Science, 67: 732–744. 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 considered. No consistent patterns in the redundancy of the ecological indicators across ecosystems emerged from the analyses, confirming that each indicator provided complementary information on ecosystem status. The different trends in indicators may reflect differing historical exploitation patterns, management, and environmental regimes in these systems. Commitment to monitoring programmes and development of system-specific baseline, target, and threshold reference levels are required. Improved understanding of the responsiveness and performance of ecological indicators to management actions are needed to address adequately whether ecosystems are recovering from, or being further impacted by, fishing, and whether management targets are being met. The relative effects of multiple environmental and ecological processes as well as multiple human-induced stressors that characterize exploited ecosystems also need to be quantified.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsp282
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2010
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  • 4
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    Redundancy in metrics describing the composition, structure, and functioning of the North Sea demersal fish community
    Oxford University Press (OUP) ; 2012
    In:  ICES Journal of Marine Science Vol. 69, No. 1 ( 2012-01-01), p. 8-22
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 69, No. 1 ( 2012-01-01), p. 8-22
    Abstract: Greenstreet, S. P. R., Fraser, H. M., Rogers, S. I., Trenkel, V. M., Simpson, S. D., and Pinnegar, J. K. 2012. Redundancy in metrics describing the composition, structure, and functioning of the North Sea demersal fish community. – ICES Journal of Marine Science, 69: 8–22. 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 objectives for particular biodiversity metrics. This issue of metric redundancy is addressed, and 15 metrics covering five main attributes of community composition, structure, and function are applied to groundfish survey data. Factor analysis suggested a new interpretation of the metric information and indicated that a minimum suite of seven metrics was necessary to ensure that all changes in the general health of the North Sea demersal fish community were monitored properly. Covariance among size-based and species-diversity metrics was low, implying that restoration of community size structure would not necessarily reverse declines in species diversity.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsr188
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2012
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  • 5
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    Close-kin mark–recapture abundance estimation: practical insights and lessons learned
    Oxford University Press (OUP) ; 2022
    In:  ICES Journal of Marine Science Vol. 79, No. 2 ( 2022-03-10), p. 413-422
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 79, No. 2 ( 2022-03-10), p. 413-422
    Abstract: We present practical lessons learned from applying the recent close-kin mark–recapture (CKMR) abundance estimation method to thornback ray (Raja clavata). For CKMR, related individuals are identified from their genotypes and their number and pattern is used for abundance estimation. We genotyped over 7000 individuals collected in the Bay of Biscay using Single Nucleotide Polymorphism (SNP) markers finding 99 parent–offspring pairs. The estimated number of adult thornback rays in the central Bay of Biscay was around 135000 (CV 0.19) in 2013. In total, four lessons were drawn: (i) CKMR helps identifying metapopulation structure, which if ignored might affect abundance estimates and/or time trends. There was strong evidence for two distinct local populations of thornback ray with no demographic connectivity. (ii) Demographic sample composition can affect precision and needs to include a range of birth years, which turned out to be difficult for thornback ray. (iii) Reasonable age information for potential offspring is essential. (iv) The sex of potential parents is needed and might be identified from sex-related SNPs. Reliable abundance estimation by CKMR appears feasible for a wide range of species provided that: sampling adequately covers potential local population structure, has appropriate demographic composition, and the age of potential offspring is reasonably well-known.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    URL: Article
    DOI: 10.1093/icesjms/fsac002
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
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    detail.hit.zdb_id: 1468003-8
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  • 6
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    Comparison of approaches for incorporating depredation on fisheries catches into Ecopath
    Oxford University Press (OUP) ; 2020
    In:  ICES Journal of Marine Science Vol. 77, No. 7-8 ( 2020-12-01), p. 3153-3167
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 77, No. 7-8 ( 2020-12-01), p. 3153-3167
    Abstract: Ecosystem-based approaches are increasingly used in fisheries management to account for the direct trophic impacts of fish population harvesting. However, fisheries can also indirectly alter ecosystem structure and functioning, for instance via the provision of new feeding opportunities to marine predators. For instance, marine depredation, where predators feed on fishery catches on fishing gear, is a behaviour developed by many marine species globally. This behaviour can modify both the ecological role of predators and fisheries performance. Yet, these ecosystem-wide effects of depredation are rarely considered holistically. In this study, we explored different ways of incorporating depredation into an Ecopath trophic model. We assessed, through a subantarctic case study, how three alternative model structures can account for depredation effects on fishery catches, predator and non-commercial prey populations, as well as target fish stocks. While none adequately addresses all facets of depredation, the alternative models can to some extent capture how depredation can lead to increased fishing pressure on stocks. As structural specificities of Ecopath prevented us from representing other depredation effects such as provisioning effects for predator populations, we conclude this study with a set of guidance to effectively capture the complex effects of depredation in marine ecosystems and fisheries models.
    Type of Medium: Online Resource
    ISSN: 1095-9289
    URL: Article
    DOI: 10.1093/icesjms/fsaa219
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
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  • 7
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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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  • 8
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    A comparison of hierarchical models for relative catch efficiency based on paired-gear data for US Northwest Atlantic fish stocks
    Canadian Science Publishing ; 2013
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 70, No. 9 ( 2013-09), p. 1306-1316
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 70, No. 9 ( 2013-09), p. 1306-1316
    Abstract: Selectivity and catch comparison studies are important for surveys that use two or more gears to collect relative abundance information. Prevailing model-based analytical methods for studies using a paired-gear design assume a binomial model for the data from each pair of gear sets. Important generalizations include nonparametric smooth size effects and normal random pair and size effects, but current methods for fitting models that account for random smooth size effects are restrictive, and observations within pairs may exhibit extra-binomial variation. I propose a hierarchical model that accounts for random smooth size effects among pairs and extra-binomial variation within pairs with a conditional beta-binomial distribution. I compared relative performance of models with different conditional distribution and random effects assumptions fit to data on 16 species from an experiment carried out in the US Northwest Atlantic Ocean comparing a new and a retiring vessel. For more than half of the species, conditional beta-binomial models performed better than binomial models, and accounting for random variation among pairs in the relative efficiency was important for all species.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2013-0136
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2013
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    detail.hit.zdb_id: 1473089-3
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  • 9
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    Optimal management of recreational fisheries in the presence of hooking mortality and noncompliance — predictions from a bioeconomic model incorporating a mechanistic model of angler behavior
    Canadian Science Publishing ; 2015
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 72, No. 1 ( 2015-01), p. 37-53
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 72, No. 1 ( 2015-01), p. 37-53
    Abstract: Using a bioeconomic model, we systematically investigated how hooking mortality and regulatory noncompliance influenced management outcomes across a range of freshwater fish species exploited by diverse angler populations. The model integrated an empirically based submodel describing the behaviour of three angler types with an age-structured fish population submodel calibrated to five life-history types (LHTs). Increased hooking mortality generally undermined regulation effectiveness, decreased socially optimal input (license numbers) and output regulations (minimum-size limits), and eroded the social welfare anglers derived from the fishery. However, the results strongly varied with LHT and angler type. Noncompliance had an isolated effect, primarily affecting fish species with low compensatory reserves when hooking mortality was low. However, in the absence of regulatory constraints on effort, noncompliance facilitated recruitment overfishing and increased the minimum-size limit required to avoid it. Despite added mortality from hooking and noncompliance, the strong dependence of angler utility on catch rates usually meant socially optimal management safeguarded biological sustainability. Yet, ignoring hooking mortality and noncompliance when predicting optimal regulations often led to population collapse. To conclude, models designed to derive recommendations for recreational fisheries management must consider both hooking mortality and noncompliance. Otherwise, dissatisfied anglers or biologically overfished stocks are possible.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2013-0650
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2015
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  • 10
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    A random effects population dynamics model based on proportions-at-age and removal data for estimating total mortality
    Canadian Science Publishing ; 2012
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 69, No. 11 ( 2012-11), p. 1881-1893
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 69, No. 11 ( 2012-11), p. 1881-1893
    Abstract: 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 model versions, including models treating mortality as fixed effects and misspecified models. All model versions were, in general, estimable, though for certain parameter values or replicate runs they were not. Relative estimation bias of final year total mortalities and depletion rates were lower for the proposed random effects model compared with the fixed effects version for total mortality. The model is demonstrated for the case of blue ling (Molva dypterygia) to the west of the British Isles for the period 1988 to 2011.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/f2012-103
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2012
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
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