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  • 1
    Online Resource
    Online Resource
    Corrigendum to “A fisheries acoustic multi-frequency indicator to inform on large scale spatial patterns of aquatic pelagic ecosystems” [Ecol. Indic. 30 (2013) 72–79]
    Elsevier BV ; 2013
    In:  Ecological Indicators Vol. 34 ( 2013-11), p. 649-
    Details
    In: Ecological Indicators, Elsevier BV, Vol. 34 ( 2013-11), p. 649-
    Type of Medium: Online Resource
    ISSN: 1470-160X
    URL: Article
    DOI: 10.1016/j.ecolind.2013.05.005
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2013
    detail.hit.zdb_id: 2063587-4
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  • 2
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    Combining time trends in multiple metrics for identifying persistent changes in population processes or environmental stressors : Combining time trends in multiple metrics
    Wiley ; 2010
    In:  Journal of Applied Ecology Vol. 47, No. 4 ( 2010-06-07), p. 751-758
    Details
    In: Journal of Applied Ecology, Wiley, Vol. 47, No. 4 ( 2010-06-07), p. 751-758
    Type of Medium: Online Resource
    ISSN: 0021-8901 , 1365-2664
    URL: Issue
    URL: Article
    DOI: 10.1111/jpe.2010.47.issue-4
    DOI: 10.1111/j.1365-2664.2010.01824.x
    Language: English
    Publisher: Wiley
    Publication Date: 2010
    detail.hit.zdb_id: 2020408-5
    detail.hit.zdb_id: 410405-5
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  • 3
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    Interannual Variability of Fisheries Economic Returns and Energy Ratios Is Mostly Explained by Gear Type
    Public Library of Science (PLoS) ; 2013
    In:  PLoS ONE Vol. 8, No. 7 ( 2013-7-29), p. e70165-
    Details
    In: PLoS ONE, Public Library of Science (PLoS), Vol. 8, No. 7 ( 2013-7-29), p. e70165-
    Type of Medium: Online Resource
    ISSN: 1932-6203
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.1371/journal.pone.0070165
    DOI: 10.1371/journal.pone.0070165.g001
    DOI: 10.1371/journal.pone.0070165.g002
    DOI: 10.1371/journal.pone.0070165.g003
    DOI: 10.1371/journal.pone.0070165.g004
    DOI: 10.1371/journal.pone.0070165.g005
    DOI: 10.1371/journal.pone.0070165.g006
    DOI: 10.1371/journal.pone.0070165.t001
    DOI: 10.1371/journal.pone.0070165.s001
    Language: English
    Publisher: Public Library of Science (PLoS)
    Publication Date: 2013
    detail.hit.zdb_id: 2267670-3
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  • 4
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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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    detail.hit.zdb_id: 1468003-8
    detail.hit.zdb_id: 29056-7
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  • 5
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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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    detail.hit.zdb_id: 1468003-8
    detail.hit.zdb_id: 29056-7
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  • 6
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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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    detail.hit.zdb_id: 1468003-8
    detail.hit.zdb_id: 29056-7
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  • 7
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    Examining the utility of alternative video monitoring metrics for indexing reef fish abundance
    Canadian Science Publishing ; 2014
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 71, No. 3 ( 2014-03), p. 464-471
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 71, No. 3 ( 2014-03), p. 464-471
    Abstract: Underwater video has become an important tool for monitoring reef fish populations worldwide because it is nonextractive and not strongly selective. A variety of approaches have been developed to enumerate fish on videos, but to our knowledge these metrics have not been tested to determine if they are proportional to true abundance. We compared the most commonly used metric, MaxN (i.e., the maximum number of fish in a single frame during the viewing interval), to a newly developed metric, MeanCount (i.e., the mean number of fish observed in a series of snapshots over a viewing interval), using simulations, a laboratory experiment, and an empirical study. MaxN was nonlinearly related to true abundance using all three approaches, providing increasingly dampened estimates of abundance with increasing true abundance (i.e., hyperstability). Therefore, MaxN may result in positively biased indices of abundance for declining fish stocks or negatively biased abundance indices when fish stocks are increasing. Alternatively, MeanCount was generally linearly related to true abundance and its variability was similar to MaxN, suggesting that MeanCount can be useful for indexing abundance of fish in underwater video surveys.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2013-0086
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2014
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    detail.hit.zdb_id: 1473089-3
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  • 8
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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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  • 9
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    A photographic method for lobster morphometry aimed at site discrimination
    Canadian Science Publishing ; 2013
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 70, No. 11 ( 2013-11), p. 1658-1665
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 70, No. 11 ( 2013-11), p. 1658-1665
    Abstract: Current data suggest that lobster (Homarus americanus) populations are less homogenous than once believed. In an effort to better discriminate morphologically among lobsters from different sites, we developed a photographic method using ImageJ and compared it with commonly used “hand” measurements. We standardized the measuring process using a strap-down board for both dorsal and ventral photographs with a camera mounted at a fixed position above the lobster. Discriminant analysis showed that both hand and photographic methods were useful in discriminating lobsters — both males and females — from three different sites. Additionally, the photographic method improved reproducibility and resolution, it reduced measurement time at the dock, and it created a permanent record for later verification, additional statistical analyses, and observer training.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2013-0103
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
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  • 10
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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
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
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