| 1. |
- Cardinale, Massimiliano, et al.
(författare)
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First Maximum Sustainable Yield advice for the Nephrops norvegicus stocks of the Northwest Iberian coast using stochastic Surplus Production model in Continuous Time (SPiCT)
- 2023
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Ingår i: Frontiers in marine science. - : Frontiers Media SA. - 2296-7745. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- The assessment of the status of fisheries resources is pivotal due to the importance of marine resources in global food security and to halt the ongoing decline in marine biodiversity. Norway lobster (Nephrops norvegicus) is one of the most valuable resources in the Northeast Atlantic. However, overfishing has caused the decline of several Nephrops stocks over the last decades, particularly in the Nephrops Functional Units (FUs) 25 (NW Spain), 26-27 (NW Spain and North Portugal) and 31 (Cantabrian Sea, North Spain). Since 2003, the information provided by the very low level of landings and fishing effort of these three stocks was insufficient to carry out an adequate analytical assessment, so the base of the assessment has been the trends from commercial catch per unit effort (CPUE). The objective of this study was to carry out the first assessment of these three stocks with an analytical MSY-based model. A review of the available data was made and the stochastic Surplus Production Model in Continuous Time (SPiCT) was fitted for each FU. The results indicate an extremely low biomass for FUs 25 and 26-27 since the mid-nineties well below the reference points. For FU 31, on the other hand, estimated biomass is larger. Our findings also identified long-term temporal and spatial changes in the population dynamic of Nephrops in the Northwest Iberian coast. The results were compare with those obtained in the same stocks with other data-limited methods. Also the role of abiotic factors on the observed dynamic of the stocks was explored. The results of this study are not only relevant for the sustainable exploitation of Norway lobster stocks off the Northwest Iberian coast but provide valuable insights into the suitability and limitations of production models for the assessment of crustacean stocks in general.
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| 2. |
- Griffiths, Christopher, et al.
(författare)
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Including older fish in fisheries management: A new age-based indicator and reference point for exploited fish stocks
- 2024
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Ingår i: Fish and Fisheries. - 1467-2960 .- 1467-2979. ; 25, s. 18-37
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Tidskriftsartikel (refereegranskat)abstract
- Larger and older fish contribute disproportionately to spawning and play an important role in the replenishment of exploited stocks. Fishing often removes specific size- and age-classes, with direct impacts on stock productivity and population resilience. Despite this, fisheries advice is commonly based on estimates of spawning stock biomass (SSB) and fishing mortality (F) and makes little reference to the importance of size and/or age structure. Consequently, there is a need for indicators of size and/or age structure to better inform fisheries management and help assess global sustainability goals. Here, we introduce a new age-based indicator ABI(MSY) that monitors age structure relative to the equilibrium age structure at F-MSY. We apply this new indicator to 72 commercially important stocks in the Northeast Atlantic, covering 26 species, which collectively contributed 86% of all commercial catches in the region in 2019. We estimate that 62% (45 stocks) currently have proportionally fewer older fish relative to F-MSY conditions, whereas 38% (27 stocks) have proportionally more older fish; we also note patterns with respect to geographic area and taxonomic family. Simulation testing demonstrated that ABI(MSY) is responsive to overfishing and generally tracks (with high sensitivity and specificity) a common measure of stock depletion, SSB relative to B-MSY. Throughout, we show that ABI(MSY) provides information on the age structure of exploited stocks that is complementary to conventional reference points for SSB and F. Further, the framework used to estimate ABI(MSY )make it well placed for integration into current advisory frameworks on fisheries management.
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| 3. |
- Winker, Henning
(författare)
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Catch per unit effort modelling for stock assessment: A summary of good practices
- 2024
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Ingår i: Fisheries Research. - 0165-7836 .- 1872-6763. ; 269
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Tidskriftsartikel (refereegranskat)abstract
- Indices of abundance based on fishery catch-per-unit-effort (CPUE) are important components of many stock assessments, particularly when fishery-independent surveys are unavailable. Standardizing CPUE to develop indices that better reflect the relative abundance requires the analyst to make numerous decisions, which are influenced by factors that include the biology of the study species, the structure of the fishery of interest, the nature of the available data, and the objectives of the analysis such as how standardized data will be used in a subsequent assessment model. Alternative choices can substantially change the index, and hence stock assessment outcomes and management decisions. To guide decisions, we provide advice on good practices in 16 areas, focusing on decision points: fishery definitions, exploring and preparing data, misreporting, data aggregation, density and catchability covariates, environmental variables, combining CPUE and survey data, analysis tools, spatial considerations, setting up and predicting from the model, uncertainty estimation, error distributions, model diagnostics, model selection, multispecies targeting, and using CPUE in stock assessments. Often the most influential outcome of exploring and analysing catch and effort data is that analysts better understand the population and the fishery, thereby improving the stock assessment.
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| 4. |
- Winker, Henning
(författare)
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Conservation successes and challenges for wide-ranging sharks and rays
- 2023
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 120
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Tidskriftsartikel (refereegranskat)abstract
- consumption of seafood, combined with the compounding effects of habitat loss, climate change, and pollution, there is a need to identify recovery paths, particularly in poorly managed and poorly monitored fisheries. Here, we document conservation through fisheries management success for 11 coastal sharks in US waters by comparing population trends through a Bayesian state-space model before and after the implementation of the 1993 Fisheries Management Plan for Sharks. We took advantage of the spatial and temporal gradients in fishing exposure and fisheries management in the Western Atlantic to analyze the effect on the Red List status of all 26 wide-ranging coastal sharks and rays. We show that extinction risk was greater where fishing pressure was higher, but this was offset by the strength of management engagement (indicated by strength of National and Regional Plan of Action for sharks and rays). The regional Red List Index (which tracks changes in extinction risk through time) declined in all regions until the 1980s but then improved in the North and Central Atlantic such that the average extinction risk is currently half that in the Southwest. Many sharks and rays are wide ranging, and successful fisheries management in one country can be undone by poorly regulated or unregulated fishing elsewhere. Our study underscores that well-enforced, science-based management of carefully monitored fisheries can achieve conservation success, even for slow-growing species.
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| 5. |
- Winker, Henning
(författare)
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Coupling state-of-the-art modelling tools for better informed Red List assessments of marine fishes
- 2024
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Ingår i: Journal of Applied Ecology. - 0021-8901 .- 1365-2664. ; 61, s. 647-657
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Tidskriftsartikel (refereegranskat)abstract
- In the face of biodiversity loss worldwide, it is paramount to quantify species' extinction risk to guide conservation efforts. The International Union for the Conservation of Nature (IUCN)'s Red List is considered the global standard for evaluating extinction risks. IUCN criteria also inform national extinction risk assessments. Bayesian models, including the state-of-the-art JARA ('Just Another Red List Assessment') tool, deliver probabilistic statements about species falling into extinction risk categories, thereby enabling characterisation and communication of uncertainty in extinction risk assessments. We coupled the state-of-the-art VAST ('Vector Autoregressive Spatio-Temporal') modelling tool and JARA, for better informed Red List assessments of marine fishes. In this framework, VAST is fitted to scientific survey catch rate data to provide indices to JARA whose uncertainty is propagated to JARA outcomes suggesting extinction risk categories (under the population reduction criterion). In addition, VAST delivers a valuable habitat assessment to better understand what may be driving extinction risk in the study region. Here, we demonstrate the coupled VAST-JARA modelling framework by applying it to five contrasting North Sea species, with or without a quantitative stock assessment and with different conservation statuses according to the latest global Red List assessments. The North Sea application coupled with previous assessments and studies suggest that, among the three elasmobranchs, starry ray is in most need of urgent research (and conservation actions where appropriate), followed by spurdog, while lesser-spotted dogfish is increasing in biomass. Moreover, both the VAST-JARA modelling framework and previous research indicate that, while European plaice is not of conservation concern, cod has likely met the IUCN criteria for being listed as Endangered recently. Synthesis and applications. The predictions of the VAST-JARA modelling framework for North Sea species, including JARA output and VAST habitat assessment, constitute valuable supporting information to make interpretations based on Red List guidelines, which will help decision-makers in their next North Sea Red List assessment. We foresee applications of the modelling framework to assist Red List assessments of numerous marine fishes worldwide. Our modelling framework has many potential advantageous uses, including informing resource management about climate change impacts on species' extinction risks.The predictions of the VAST-JARA modelling framework for North Sea species, including JARA output and VAST habitat assessment, constitute valuable supporting information to make interpretations based on Red List guidelines, which will help decision-makers in their next North Sea Red List assessment. We foresee applications of the modelling framework to assist Red List assessments of numerous marine fishes worldwide. Our modelling framework has many potential advantageous uses, including informing resource management about climate change impacts on species' extinction risks.image
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| 6. |
- Winker, Henning
(författare)
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Good practices for surplus production models
- 2024
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Ingår i: Fisheries Research. - 0165-7836 .- 1872-6763. ; 275
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Tidskriftsartikel (refereegranskat)abstract
- Surplus production models (SPMs) have a long history in fisheries ecology and are important for the assessment and management of marine species and stocks. However, the implementation, application, and usage of these models vary across regions and case studies. Good practice guidelines can streamline modelling workflows, inform the acceptance or rejection of an assessment, and facilitate the derivation of management advice from accepted assessments. This paper discusses current practices in the application of SPMs and proposes good practice guidelines for their use in stock assessment. We complement our recommendations with results from a simulation study examining the performance of an age-based operating model and a SPM assessment model under 60 scenarios with various assumptions regarding data quantity, quality, and model priors. We provide specific good practice guidelines for two widely used state-space SPMs: SPiCT and JABBA. Finally, we discuss current limitations and suggest avenues for future developments for SPMs.
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