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  • 1
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    Status and rebuilding of European fisheries (2018)
    Elsevier
    In:  Marine Policy, 93 . pp. 159-170.
    Details
    Publication Date: 2021-03-19
    Description: Since January 2014, the reformed Common Fisheries Policy (CFP) of the European Union is legally binding for all Member States. It prescribes the end of overfishing and the rebuilding of all stocks above levels that can produce maximum sustainable yields (MSY). This study examines the current status, exploitation pattern, required time for rebuilding, future catch, and future profitability for 397 European stocks. Fishing pressure and biomass were estimated from 2000 to the last year with available data in 10 European ecoregions and 2 wide ranging regions. In the last year with available data, 69% of the 397 stocks were subject to ongoing overfishing and 51% of the stocks were outside of safe biological limits. Only 12% of the stocks fulfilled the prescriptions of the CFP. Fishing pressure has decreased since 2000 in some ecoregions but not in others. Barents Sea and Norwegian Sea have the highest percentage (〉60%) of sustainably exploited stocks that are capable of producing MSY. In contrast, in the Mediterranean Sea, fewer than 20% of the stocks are exploited sustainably. Overfishing is still widespread in European waters and current management, which aims at maximum sustainable exploitation, is unable to rebuild the depleted stocks and results in poor profitability. This study examines four future exploitation scenarios that are compatible with the CFP. It finds that exploitation levels of 50–80% of the maximum will rebuild stocks and lead to higher catches than currently obtained, with substantially higher profits for the fishers.
    Type: Article , PeerReviewed
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    DOI: 10.1016/j.marpol.2018.04.018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    A new approach for estimating stock status from length frequency data (2018)
    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 75 (6). pp. 2004-2015.
    Details
    Publication Date: 2021-02-08
    Description: This study presents a new method (LBB) for the analysis of length frequency data from commercial catches. LBB works for species that grow throughout their lives, such as most commercially-important fish and invertebrates, and requires no input in addition to length frequency data. It estimates asymptotic length, length at first capture, relative natural mortality, and relative fishing mortality. Standard fisheries equations can then be used to approximate current exploited biomass relative to unexploited biomass. In addition, these parameters allow the estimation of length at first capture that would maximize catch and biomass for a given fishing effort, and estimation of a proxy for the relative biomass capable of producing maximum sustainable yields. Relative biomass estimates of LBB were not significantly different from the “true” values in simulated data and were similar to independent estimates from full stock assessments. LBB also presents a new indicator for assessing whether an observed size structure is indicative of a healthy stock. LBB results will obviously be misleading if the length frequency data do not represent the size composition of the exploited size range of the stock or if length frequencies resulting from the interplay of growth and mortality are masked by strong recruitment pulses.
    Type: Article , PeerReviewed
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    DOI: 10.1093/icesjms/fsy078
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Minimizing the Impact of Fishing (2016)
    Wiley
    In:  Fish and Fisheries, 17 (3). pp. 785-802.
    Details
    Publication Date: 2020-11-23
    Description: Minimizing the impact of fishing is an explicit goal in international agreements as well as in regional directives and national laws. To assist in practical implementation, three simple rules for fisheries management are proposed in this study: 1) take less than nature by ensuring that mortality caused by fishing is less than the natural rate of mortality; 2) maintain population sizes above half of natural abundance, at levels where populations are still likely to be able to fulfil their ecosystem functions as prey or predator; and 3) let fish grow and reproduce, by adjusting the size at first capture such that the mean length in the catch equals the length where the biomass of an unexploited cohort would be maximum (Lopt). For rule 3), the basic equations describing growth in age-structured populations are re-examined and a new optimum length for first capture (Lc_opt) is established. For a given rate of fishing mortality, Lc_opt keeps catch and profit near their theoretical optima while maintaining large population sizes. Application of the three rules would not only minimize the impact of fishing on commercial species, it may also achieve several goals of ecosystem-based fisheries management, such as rebuilding the biomass of prey and predator species in the system and reducing collateral impact of fishing, because with more fish in the water, shorter duration of gear deployment is needed for a given catch. The study also addresses typical criticisms of these common sense rules for fisheries management.
    Type: Article , PeerReviewed
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    DOI: 10.1111/faf.12146
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Reply to Andersen et al.(2016) "Assumptions behind size-based ecosystem models are realistic" (2016)
    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 73 (6). pp. 1656-1658.
    Details
    Publication Date: 2019-02-01
    Description: In a recent publication (Froese et al., ICES Journal of Marine Science; doi:10.1093/icesjms/fsv122), we presented a critique of the balanced harvesting (BH) approach to fishing. A short section dealt with the size-spectrum models used to justify BH, wherein we pointed out the lack of realism of these models, which mostly represented ecosystems as consisting of a single cannibalistic species. Andersen et al. (ICES Journal of Marine Science; doi:10.1093/icesjms/fsv211) commented on our paper and suggested that we criticized size-spectrum models in general and that we supposedly made several erroneous statements. We stress that we only referred to the size-spectrum models that we cited, and we respond to each supposedly erroneous statement. We still believe that the size-spectrum models used to justify BH were highly unrealistic and not suitable for evaluating real-world fishing strategies. We agree with Andersen et al. that BH is unlikely to be a useful guiding principle for ecosystem-based fisheries management, for many reasons. The use of unrealistic models is one of them.
    Type: Article , PeerReviewed
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    DOI: 10.1093/icesjms/fsv273
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Size still matters. A response to Svedäng (2013): Size matters: Ne quid nimis (2015)
    Elsevier
    In:  Fisheries Research, 164 . pp. 329-330.
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    Publication Date: 2017-04-13
    Description: Letter to the Editor
    Type: Article , PeerReviewed
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    DOI: 10.1016/j.fishres.2014.10.008
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Estimating Fisheries Reference Points from Catch and Resilience (2017)
    Wiley
    In:  Fish and Fisheries, 18 (3). pp. 506-526.
    Details
    Publication Date: 2020-07-23
    Description: This study presents a Monte Carlo method (CMSY) for estimating fisheries reference points from catch, resilience and qualitative stock status information on data-limited stocks. It also presents a Bayesian state-space implementation of the Schaefer production model (BSM), fitted to catch and biomass or catch-per-unit-of-effort (CPUE) data. Special emphasis was given to derive informative priors for productivity, unexploited stock size, catchability and biomass from population dynamics theory. Both models gave good predictions of the maximum intrinsic rate of population increase r, unexploited stock size k and maximum sustainable yield MSY when validated against simulated data with known parameter values. CMSY provided, in addition, reasonable predictions of relative biomass and exploitation rate. Both models were evaluated against 128 real stocks, where estimates of biomass were available from full stock assessments. BSM estimates of r, k and MSY were used as benchmarks for the respective CMSY estimates and were not significantly different in 76% of the stocks. A similar test against 28 data-limited stocks, where CPUE instead of biomass was available, showed that BSM and CMSY estimates of r, k and MSY were not significantly different in 89% of the stocks. Both CMSY and BSM combine the production model with a simple stock–recruitment model, accounting for reduced recruitment at severely depleted stock sizes.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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    DOI: 10.1111/faf.12190
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    How can we minimize the impact of fishing? (2017)
    In:  Environmental Science Journal for Teens, 2017 (November). pp. 1-4.
    Details
    Publication Date: 2018-01-15
    Description: How many times do you think you have eaten fish this year? Fish is delicious and it’s really good for you, but we need to make sure that we don’t over-fish our seas and oceans (Fig. 1). That way there are enough fish left to feed us for all the years to come. We propose three simple rules for fisheries management, which would reduce the impact of fishing on the major fish species. The rules would also help to rebalance the ecosystems and reduce the damage that fishing causes when boats scrape their nets over the seabed to catch fish.
    Type: Article , NonPeerReviewed
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    OceanRep: Article in a Scientific Journal - without review
  • 8
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    Learning from the peer review of ‘Estimating stock status from relative abundance and resilience’ (2020)
    Institute for the Oceans and Fisheries, University of British Columbia
    In:  In: Marine and Freshwater Miscellanea II. , ed. by Pauly, D. and Ruiz-Leotaud, V. Fisheries Centre Research Reports, 28 (2). Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, BC, Canada, pp. 111-124.
    Details
    Publication Date: 2020-03-19
    Description: This contribution presents the detailed responses to the peer-review of Froese et al. (2019) “Estimating stock status from relative abundance and resilience” (ICES J. Mar. Sci. 2019) which outlined a method called “AMSY” for inferring biomass trends for stocks for which only catch-per-unit-effort and limited ancillary (‘priors’) data are available. The responses emphasize that the required priors are legitimate and straightforward to obtain, thus, making AMSY a method of choice in data-sparse situations. This is also a good example of the role of peer-review in validating and improving science.
    Type: Book chapter , NonPeerReviewed
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    OceanRep: Book chapter
  • 9
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    A critique of the balanced harvesting approach to fishing (2016)
    ICES
    In:  ICES Journal of Marine Science, 73 (6). pp. 1640-1650.
    Details
    Publication Date: 2019-09-23
    Description: The approach to fisheries termed “balanced harvesting” (BH) calls for fishing across the widest possible range of species, stocks, and sizes in an ecosystem, in proportion to their natural productivity, so that the relative size and species composition is maintained. Such fishing is proposed to result in higher catches with less negative impact on exploited populations and ecosystems. This study examines the models and the empirical evidence put forward in support of BH. It finds that the models used unrealistic settings with regard to life history (peak of cohort biomass at small sizes), response to fishing (strong compensation of fishing mortality by reduced natural mortality), and economics (uniform high cost of fishing and same ex-vessel price for all species and sizes), and that empirical evidence of BH is scarce and questionable. It concludes that evolutionary theory, population dynamics theory, ecosystem models with realistic assumptions and settings, and widespread empirical evidence do not support the BH proposal. Rather, this body of evidence suggests that BH will not help but will hinder the policy changes needed for the rebuilding of ecosystems, healthy fish populations, and sustainable fisheries.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1093/icesjms/fsv122
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    How can we reduce the impact of fishing? (2017)
    In:  Science Journal for Kids, 2017 . pp. 1-4.
    Details
    Publication Date: 2017-11-30
    Type: Article , NonPeerReviewed
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    OceanRep: Article in a Scientific Journal - without review
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