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  • 1
    Online Resource
    Online Resource
    A stock rebuilding algorithm featuring risk assessment and an optimization strategy of single or multispecies fisheries
    Oxford University Press (OUP) ; 2007
    In:  ICES Journal of Marine Science Vol. 64, No. 6 ( 2007-09-01), p. 1101-1115
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 64, No. 6 ( 2007-09-01), p. 1101-1115
    Abstract: Gröger, J. P., Rountree, R. A., Missong, M., and Rätz, H-J. 2007. A stock rebuilding algorithm featuring risk assessment and an optimization strategy of single or multispecies fisheries. – ICES Journal of Marine Science, 64: 1101–1115. We present a simple but flexible stock-rebuilding algorithm model that features ideas of risk assessment, with all constraints set up explicitly, and with clear optimality for controlling fishing effort (or fishing mortality) and maximizing landings (or economic value). In contrast to the conventional approach, our approach does not predict future stock development from historical stock dynamics, but provides directly optimal annual F values and associated optimum catch quotas for a given planning horizon. Hence, the F values are not estimated retrospectively, but are realizations of a control variable created through the optimization process. The optimal solution is based on maximization of a non-linearly constrained objective function for catch or yield, whereas the constraints inter alia include biomass targets, F limits, and stable catch. We present the basic theory together with selected model variants, such as inclusion of biological interactions and integration of elements of risk assessment. The optimization procedure outlined here is not only “risk averse” but a risk minimization procedure in itself. It can be applied in a deterministic or stochastic decision-making process as well as within a single or multispecies context. We illustrate the approach with a simplified (deterministic) multispecies fisheries management and a (stochastic) single-species risk assessment example.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsm085
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2007
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  • 2
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    Sustainable management of mixed demersal fisheries in the North Sea through fleet-based management—a proposal from a biological perspective
    Oxford University Press (OUP) ; 2007
    In:  ICES Journal of Marine Science Vol. 64, No. 4 ( 2007-05-01), p. 652-660
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 64, No. 4 ( 2007-05-01), p. 652-660
    Abstract: Rätz, H-J., Bethke, E., Dörner, H., Beare, D., and Gröger, J. 2007. Sustainable management of mixed demersal fisheries in the North Sea through fleet-based management—a proposal from a biological perspective. – ICES Journal of Marine Science, 64: 652–660. Cod, haddock, whiting, saithe, plaice, sole, and Norway lobster are main target species for the mixed demersal fisheries of the North Sea, Skagerrak, and eastern Channel. Management by total allowable catch has not been able to constrain exploitation of individual species, so the potential for a fleet-specific effort management system to reach the management objectives established for the stocks is simulated. Relative fleet-specific effort factors are estimated based on the sum of partial fishing mortalities of the species caught, weighted by the stocks at risk of reduced reproductive capacity. The strategy promotes the use of selective gear and levies non-selective gear. The factors were applied in medium-term simulations of the annual decision process in accordance with existing and proposed multi-annual management plans (including for cod recovery). Strict effort reduction would be required for fleets targeting cod, plaice, or sole (specifically large- and medium-mesh trawler fleets, beam trawlers, and gillnetters) for ∼5 years, reducing the exploitation rates on all stocks substantially. Cod and plaice are predicted to recover by 2010 and cod catches to exceed recent levels continually, with the more selective longliners and some other gear types profiting most. Management objectives for cod dominate annual effort adjustments, resulting in substantial underexploitation of other stocks. However, even a 10% bias caused by non-compliance would largely halt cod recovery and the restoration of other stocks.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsm030
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2007
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  • 3
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    Challenging the links between seafood and human health in the context of global change
    Cambridge University Press (CUP) ; 2016
    In:  Journal of the Marine Biological Association of the United Kingdom Vol. 96, No. 1 ( 2016-02), p. 29-42
    Details
    In: Journal of the Marine Biological Association of the United Kingdom, Cambridge University Press (CUP), Vol. 96, No. 1 ( 2016-02), p. 29-42
    Abstract: Living marine resources have strong links with human health and well-being that are complex, still not well understood and that are being modified by global change. This review attempts to illustrate how fishing activities, aquaculture and climate change are challenging these connections and the consequent health risks and benefits posed to citizens. Although global change may provide some positive aspects for human health locally, such as new sources of omega-3, overall it will exacerbate existing seafood security and safety concerns. Unsustainable fishing and aquaculture practices, and climate change, particularly sea warming, ocean acidification and changes in riverine runoff, are threatening not only the protein and fish oil/omega-3 supplies available for consumers, but also raising ecological and health concerns associated with the increase of contaminants, microbes and biotoxins. In this context, we propose a number of management measures that could mitigate the negative effects of global change on seafood, and hence on human health and well-being.
    Type of Medium: Online Resource
    ISSN: 0025-3154 , 1469-7769
    URL: Article
    DOI: 10.1017/S0025315415001988
    RVK:
    WA 15000
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2016
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  • 4
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    An alternative reference point in the context of ecosystem-based fisheries management: maximum sustainable dead biomass
    Oxford University Press (OUP) ; 2015
    In:  ICES Journal of Marine Science Vol. 72, No. 8 ( 2015-10-01), p. 2257-2268
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 72, No. 8 ( 2015-10-01), p. 2257-2268
    Abstract: Under the 2013 Reform of the European Union's Common Fisheries Policy (CFP), fisheries management aims to ensure that, within a reasonable time frame, the exploitation of marine biological resources restores and maintains populations of harvested stocks above levels that can produce the maximum sustainable yield (MSY). The CFP also calls for the implementation of an ecosystem-based approach to fisheries management (EBFM). In this paper, we present the concept of maximum sustainable dead biomass (MSDB) and its associated management reference points for fishing mortality and spawning-stock biomass as alternatives to those associated with MSY. The concept of MSDB is illustrated by a dynamic pool production model of a virtual fish stock which takes into account variations in natural mortality (M), fishing mortality (F), and exploitation pattern. Our approach implies a compensatory mechanism whereby survivors may benefit from compensatory density dependence and is implemented through progressive substitution of M with F for varying rates of total mortality (Z). We demonstrate that the reference points for fishing mortality and spawning-stock biomass associated with MSDB are less sensitive to increasing compensation of M with F than those associated with MSY and more sensitive to changes in selection pattern. MSDB-based reference points, which are consistent with maximum stock productivity, are also associated with lower fishing mortality rates and higher stock biomasses than their MSY-based counterparts. Given that selection pattern can be influenced through fishery input measures (e.g. technical gear measures, decisions on areas, and/or times of fishing), whereas variations of M in response to F are not controllable (indeed poorly understood), that the results of many fish stock assessments are imprecise, that maximum stock productivity corresponds to MSDB and that MSY-based reference points may best be considered as limits, we propose that MSDB-based reference points provide a more appropriate basis for management under an EBFM.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsv089
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2015
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  • 5
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    The poor health of deep‐water species in the context of fishing activity and a warming climate: will populations of Molva species rebuild or collapse?
    Wiley ; 2021
    In:  Journal of Fish Biology Vol. 98, No. 6 ( 2021-06), p. 1572-1584
    Details
    In: Journal of Fish Biology, Wiley, Vol. 98, No. 6 ( 2021-06), p. 1572-1584
    Abstract: Many deep‐water fish populations, being K‐selected species, have little resilience to overexploitation and may be at serious risk of depletion as a consequence. Sea warming represents an additional threat. In this study, the condition, or health, of several populations of common ling ( Molva molva ), blue ling ( Molva dypterygia ) and Mediterranean or Spanish ling ( Molva macrophthalma ) inhabiting different areas in the North Atlantic and the Mediterranean was evaluated, to shed light on the challenges these deep‐water species are facing in the context of fishing activity and a warming climate. The data on the condition of Molva populations which are analysed here have been complemented with data on abundance and, for the southernmost species (Mediterranean ling), with two other health indicators (parasitism and hepato‐somatic index). Despite some exceptions ( e.g. , common ling in Icelandic waters), this study shows that the condition of many populations of Molva s pecies in the northeastern Atlantic and the Mediterranean Sea has worsened, a trend which, in recent decades, has usually been found to be accompanied by a decline in their abundance. In addition, the poor health status of most populations of common ling, blue ling and Mediterranean ling considered in this analysis points to a lower sustainability of these populations in the future. Overall, the health status and abundance of Molva populations in the northeastern Atlantic and the Mediterranean suggest that only some populations located in the North Atlantic may be able to rebuild, whereas the populations in southern North Atlantic and the Mediterranean, which are probably most at risk from sea warming, are facing serious difficulties in doing so. In the context of fisheries and global warming, this study's results strongly indicate that management bodies need to consider the health status of many of the populations of Molva species, particularly in southern European waters, before implementing their decisions.
    Type of Medium: Online Resource
    ISSN: 0022-1112 , 1095-8649
    URL: Issue
    URL: Article
    DOI: 10.1111/jfb.v98.6
    DOI: 10.1111/jfb.14347
    Language: English
    Publisher: Wiley
    Publication Date: 2021
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  • 6
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    Optimising sustainable management of mixed fisheries: Differentiating and weighting selective strategies
    Elsevier BV ; 2016
    In:  Ocean & Coastal Management Vol. 134 ( 2016-12), p. 150-162
    Details
    In: Ocean & Coastal Management, Elsevier BV, Vol. 134 ( 2016-12), p. 150-162
    Type of Medium: Online Resource
    ISSN: 0964-5691
    URL: Article
    DOI: 10.1016/j.ocecoaman.2016.10.005
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2016
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  • 7
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    Inter-species quota flexibility – Exploring a new management tool in European Common Fisheries Policy
    Elsevier BV ; 2018
    In:  Ocean & Coastal Management Vol. 163 ( 2018-09), p. 222-231
    Details
    In: Ocean & Coastal Management, Elsevier BV, Vol. 163 ( 2018-09), p. 222-231
    Type of Medium: Online Resource
    ISSN: 0964-5691
    URL: Article
    DOI: 10.1016/j.ocecoaman.2018.06.017
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2018
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  • 8
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    Long-term variability of growth and recruitment of cod (Gadus morhua) off Greenland
    Oxford University Press (OUP) ; 2005
    In:  ICES Journal of Marine Science Vol. 62, No. 7 ( 2005-01-01), p. 1310-1321
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 62, No. 7 ( 2005-01-01), p. 1310-1321
    Abstract: Growth variation was estimated from mean lengths-at-ages 4 and 5 for Atlantic cod off Greenland based on 52 973 fish taken from commercial and scientific catches from 1955 to 2002. Mean length-at-age values were corrected for area and seasonal effects, and significant growth reductions occurred during the 1960s and from the mid-1970s until the mid-1980s. Annual growth rates of cod in Greenland waters during the most recent decade (1993–2002) were consistently among the highest recorded. Statistical growth models accounting for temperature, fishing mortality, and stock abundance effects were constructed. Multiple linear regressions revealed significant positive temperature effects on growth of both age groups and a significant negative stock density effect on length-at-age 4. Correlations between exploitation intensity and length-at-age were statistically insignificant. During the period 1955–2002, the number of recruits at age 3 was significantly correlated with the Greenland cod spawning-stock biomass, June water temperature on top of Fyllas Bank (West Greenland), and Iceland cod recruitment. All factors had a positive effect on the number of Greenland recruits and, combined, accounted for 60% of the observed variation. Spawning stock size was, by far, the most important factor contributing to recruitment variability, while June water temperature below 1°C and Iceland recruits below 150 million never coincided with high year-class strength in Greenland during the past 50 years. Thus, previous conclusions regarding a close relation between the Greenland and Icelandic cod stocks might need to be reconsidered in the light of a continued recruitment failure in Greenland waters over the two most recent decades, despite the improved environmental conditions and near-average recruitment of the Icelandic stock. The low precision of the recruitment model, however, prevents reliable predictions in the short or medium term, but a substantial short-term recovery of the Greenland cod stock remains unlikely.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1016/j.icesjms.2005.07.009
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2005
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  • 9
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    Variation in fish condition between Atlantic cod (Gadus morhua) stocks, the effect on their productivity and management implications
    Elsevier BV ; 2003
    In:  Fisheries Research Vol. 60, No. 2-3 ( 2003-2), p. 369-380
    Details
    In: Fisheries Research, Elsevier BV, Vol. 60, No. 2-3 ( 2003-2), p. 369-380
    Type of Medium: Online Resource
    ISSN: 0165-7836
    URL: Article
    DOI: 10.1016/S0165-7836(02)00132-7
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2003
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    detail.hit.zdb_id: 1497860-X
    SSG: 21,3
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  • 10
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    Commentary to J.F. Caddy’s paper “Criteria for sustainable fisheries on juveniles illustrated for Mediterranean hake: control the juvenile harvest, and safeguard spawning refugia to rebuild population fecundity”
    Editorial CSIC ; 2015
    In:  Scientia Marina Vol. 79, No. 3 ( 2015-09-30), p. 301-302
    Details
    In: Scientia Marina, Editorial CSIC, Vol. 79, No. 3 ( 2015-09-30), p. 301-302
    Type of Medium: Online Resource
    ISSN: 1886-8134 , 0214-8358
    Uniform Title: Commentary to J.F. Caddy’s paper “Criteria for sustainable fisheries on juveniles illustrated for Mediterranean hake: control the juvenile harvest, and safeguard spawning refugia to rebuild population fecundity”
    URL: Issue
    URL: Article
    DOI: 10.3989/scimar.2015.79n3
    DOI: 10.3989/scimar.04269.09A
    Language: English , English
    Publisher: Editorial CSIC
    Publication Date: 2015
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