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  • 1
    In: Nature Sustainability, Springer Science and Business Media LLC, Vol. 5, No. 12 ( 2022-10-24), p. 1027-1039
    Type of Medium: Online Resource
    ISSN: 2398-9629
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2917573-2
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  • 2
    Online Resource
    Online Resource
    Canadian Science Publishing ; 2016
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 73, No. 4 ( 2016-04), p. 666-676
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 73, No. 4 ( 2016-04), p. 666-676
    Abstract: Ecosystem modeling is becoming an integral part of fisheries management, but there is a need to identify differences between predictions derived from models employed for scientific and management purposes. Here, we compared two models: a biomass-based food-web model (Ecopath with Ecosim (EwE)) and a size-structured fish community model. The models were compared with respect to predicted ecological consequences of fishing to identify commonalities and differences in model predictions for the California Current fish community. We compared the models regarding direct and indirect responses to fishing on one or more species. The size-based model predicted a higher fishing mortality needed to reach maximum sustainable yield than EwE for most species. The size-based model also predicted stronger top-down effects of predator removals than EwE. In contrast, EwE predicted stronger bottom-up effects of forage fisheries removal. In both cases, the differences are due to the presumed degree of trophic overlap between juveniles of large-bodied fish and adult stages of forage fish. These differences highlight how each model’s emphasis on distinct details of ecological processes affects its predictions, underscoring the importance of incorporating knowledge of model assumptions and limitation, possibly through using model ensembles, when providing model-based scientific advice to policy makers.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2016
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    detail.hit.zdb_id: 1473089-3
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  • 3
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2019
    In:  ICES Journal of Marine Science Vol. 76, No. 1 ( 2019-01-01), p. 124-135
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 76, No. 1 ( 2019-01-01), p. 124-135
    Abstract: Contemporary stock assessment models used by fisheries management often assume that natural mortality rates are constant over time for exploited fish stocks. This assumption results in biased estimates of fishing mortality and reference points when mortality changes over time. However, it is difficult to distinguish changes in natural mortality from changes in fishing mortality, selectivity, and recruitment. Because changes in size structure can be indicate changes in mortality, one potential solution is to use population size-structure and fisheries catch data to simultaneously estimate time-varying natural and fishing mortality. Here we test that hypothesis, using a simulation experiment to test performance for four alternative estimation models that estimate natural and fishing mortality from size structure and catch data. We show that it is possible to estimate time-varying natural mortality in a size-based model, even when fishing mortality, recruitment, and selectivity are changing over time. Finally, we apply the model to North Sea sprat, and show that estimates of recruitment and natural mortality are similar to estimates from an alternative multispecies population model fitted to additional data sources. We recommend exploring potential trends in natural mortality in forage fish assessments using tools such as the one presented here.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2463178-4
    detail.hit.zdb_id: 1468003-8
    detail.hit.zdb_id: 29056-7
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  • 4
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2022
    In:  ICES Journal of Marine Science Vol. 79, No. 4 ( 2022-05-23), p. 1120-1132
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 79, No. 4 ( 2022-05-23), p. 1120-1132
    Abstract: The environmental conditions that marine populations experience are being altered because of climate change. In particular, changes in temperature and increased variability can cause shifts in spatial distribution, leading to changes in local physiological rates and recruitment success. Yet, management of fish stocks rarely accounts for variable spatial dynamics or changes in movement rates when estimating management quantities such as stock abundance or maximum sustainable yield. To address this concern, a management strategy evaluation (MSE) was developed to evaluate the robustness of the international management system for Pacific hake, an economically important migratory stock, by incorporating spatio-temporal population dynamics. Alternative hypotheses about climate-induced changes in age-specific movement rates, in combination with three different harvest control rules (HCR), were evaluated using a set of simulations that coupled single-area estimation models with alternative operating models representing spatial stock complexity. Movement rates intensified by climate change caused a median decline in catches, increased annual catch variability, and lower average spawning biomass. Impacts varied by area and HCR, underscoring the importance of spatial management. Incorporating spatial dynamics and climate change effects into management procedures for fish stocks with spatial complexity is warranted to mitigate risk and uncertainty for exploited marine populations.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2463178-4
    detail.hit.zdb_id: 1468003-8
    detail.hit.zdb_id: 29056-7
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    SSG: 21,3
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  • 5
    In: Reviews in Fish Biology and Fisheries, Springer Science and Business Media LLC, Vol. 29, No. 3 ( 2019-9), p. 711-733
    Type of Medium: Online Resource
    ISSN: 0960-3166 , 1573-5184
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 30768-3
    detail.hit.zdb_id: 1498719-3
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  • 6
    Online Resource
    Online Resource
    Wiley ; 2017
    In:  Fish and Fisheries Vol. 18, No. 2 ( 2017-03), p. 199-211
    In: Fish and Fisheries, Wiley, Vol. 18, No. 2 ( 2017-03), p. 199-211
    Abstract: Managing fisheries presents trade‐offs between objectives, for example yields, profits, minimizing ecosystem impact, that have to be weighed against one another. These trade‐offs are compounded by interacting species and fisheries at the ecosystem level. Weighing objectives becomes increasingly challenging when managers have to consider opposing objectives from different stakeholders. An alternative to weighing incomparable and conflicting objectives is to focus on win–wins until Pareto efficiency is achieved: a state from which it is impossible to improve with respect to any objective without regressing at least one other. We investigate the ecosystem‐level efficiency of fisheries in five large marine ecosystems ( LME s) with respect to yield and an aggregate measure of ecosystem impact using a novel calibration of size‐based ecosystem models. We estimate that fishing patterns in three LME s (North Sea, Barents Sea and Benguela Current) are nearly efficient with respect to long‐term yield and ecosystem impact and that efficiency has improved over the last 30 years. In two LME s (Baltic Sea and North East US Continental Shelf), fishing is inefficient and win–wins remain available. We additionally examine the efficiency of North Sea and Baltic Sea fisheries with respect to economic rent and ecosystem impact, finding both to be inefficient but steadily improving. Our results suggest the following: (i) a broad and encouraging trend towards ecosystem‐level efficiency of fisheries; (ii) that ecosystem‐scale win–wins, especially with respect to conservation and profits, may still be common; and (iii) single‐species assessment approaches may overestimate the availability of win–wins by failing to account for trade‐offs across interacting species.
    Type of Medium: Online Resource
    ISSN: 1467-2960 , 1467-2979
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2024569-5
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  • 7
    Online Resource
    Online Resource
    Wiley ; 2018
    In:  Fish and Fisheries Vol. 19, No. 5 ( 2018-09), p. 791-797
    In: Fish and Fisheries, Wiley, Vol. 19, No. 5 ( 2018-09), p. 791-797
    Abstract: Forage fish are a vital part of marine ecosystems, partly by supporting some of the largest fisheries worldwide, but also due to their role in food webs as prey for larger fish and other predators. One of the unresolved questions about forage fish dynamics is the causes of their significant temporal fluctuations. These fluctuations are often attributed to changes in environmental conditions, but direct correlations have proven hard to find. Here, we show how time‐varying predation mortality additionally plays a substantial role in forage fish population fluctuations. By analysing 10 stocks that have estimates of natural mortality changes through time, we find that natural mortality on average increases as population biomass declines towards a trough, and to a lesser degree decreases, when their biomass is growing towards a peak. While depensatory mortality was dominant on average in biomass dynamics leading up to peaks or troughs, some of the stocks exhibited compensatory mortality emphasizing variation between stocks. Furthermore, we show that the magnitude of natural mortality and productivity is generally higher than fishing mortality. The results underscore the importance of top‐down control on the dynamics of forage fish. We conclude that a holistic ecosystem analysis is required for a better ecological understanding of forage fish dynamics.
    Type of Medium: Online Resource
    ISSN: 1467-2960 , 1467-2979
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2024569-5
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  • 8
    In: Fish and Fisheries, Wiley, Vol. 23, No. 4 ( 2022-07), p. 800-811
    Abstract: Wild‐caught fish are a bioavailable source of nutritious food that, if managed strategically, could enhance diet quality for billions of people. However, optimising nutrient production from the sea has not been a priority, hindering development of nutrition‐sensitive policies. With fisheries management increasingly effective at rebuilding stocks and regulating sustainable fishing, we can now begin to integrate nutritional outcomes within existing management frameworks. Here, we develop a conceptual foundation for managing fisheries for multispecies Maximum Nutrient Yield (mMNY). We empirically test our approach using size‐based models of North Sea and Baltic Sea fisheries and show that mMNY is predicted by the relative contribution of nutritious species to total catch and their vulnerability to fishing, leading to trade‐offs between catch and specific nutrients. Simulated nutrient yield curves suggest that vitamin D, which is deficient in Northern European diets, was underfished at fishing levels that returned maximum catch weights. Analysis of global catch data shows there is scope for nutrient yields from most of the world's marine fisheries to be enhanced through nutrient‐sensitive fisheries management. With nutrient composition data now widely available, we expect our mMNY framework to motivate development of nutrient‐based reference points in specific contexts, such as data‐limited fisheries. Managing for mMNY alongside policies that promote access to fish could help close nutrient gaps for coastal populations, maximising the contribution of wild‐caught fish to global food and nutrition security.
    Type of Medium: Online Resource
    ISSN: 1467-2960 , 1467-2979
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2024569-5
    SSG: 21,3
    SSG: 12
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  • 9
    Online Resource
    Online Resource
    Wiley ; 2017
    In:  Fish and Fisheries Vol. 18, No. 4 ( 2017-07), p. 656-667
    In: Fish and Fisheries, Wiley, Vol. 18, No. 4 ( 2017-07), p. 656-667
    Abstract: Fisheries advice is based on demographic calculations, which assume that density‐dependent processes regulating recruitment occur only in early life. This assumption is challenged by laboratory and lake studies and some recent indications from marine systems that demonstrate density‐dependent regulation late in life. By accounting for spatial dynamics of a population, something that has previously been ignored in models of fish, we show that density‐dependent regulation is determined by the size of the habitat: in small habitats, for example small lakes, regulation occurs late in life, while it can occur early in large habitats. When regulation happens late in life, fisheries yield is maximized by exploitation of mainly juvenile fish, while exploiting mature fish maximizes yield if regulation happens early. We review and interpret observations of density dependence in the light of the theory. Our results challenge the current assumption that density dependence always occurs early in life and highlights the need for an increased understanding of density‐dependent processes. This can only come about by a change of focus from determining stock‐recruitment relationships towards understanding when and how density‐dependent regulation occurs in nature.
    Type of Medium: Online Resource
    ISSN: 1467-2960 , 1467-2979
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2024569-5
    SSG: 21,3
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    Wiley ; 2019
    In:  Fish and Fisheries Vol. 20, No. 5 ( 2019-09), p. 1034-1050
    In: Fish and Fisheries, Wiley, Vol. 20, No. 5 ( 2019-09), p. 1034-1050
    Abstract: Analysing how fish populations and their ecological communities respond to perturbations such as fishing and environmental variation is crucial to fisheries science. Researchers often predict fish population dynamics using species‐level life‐history parameters that are treated as fixed over time, while ignoring the impact of intraspecific variation on ecosystem dynamics. However, there is increasing recognition of the need to include processes operating at ecosystem levels (changes in drivers of productivity) while also accounting for variation over space, time and among individuals. To address similar challenges, community ecologists studying plants, insects and other taxa increasingly measure phenotypic characteristics of individual animals that affect fitness or ecological function (termed “functional traits”). Here, we review the history of trait‐based methods in fish and other taxa, and argue that fisheries science could see benefits by integrating trait‐based approaches within existing fisheries analyses. We argue that measuring and modelling functional traits can improve estimates of population and community dynamics, and rapidly detect responses to fishing and environmental drivers. We support this claim using three concrete examples: how trait‐based approaches could account for time‐varying parameters in population models; improve fisheries management and harvest control rules; and inform size‐based models of marine communities. We then present a step‐by‐step primer for how trait‐based methods could be adapted to complement existing models and analyses in fisheries science. Finally, we call for the creation and expansion of publicly available trait databases to facilitate adapting trait‐based methods in fisheries science, to complement existing public databases of life‐history parameters for marine organisms.
    Type of Medium: Online Resource
    ISSN: 1467-2960 , 1467-2979
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2024569-5
    SSG: 21,3
    SSG: 12
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