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1
Bentley, Nokome. "Data and time poverty in fisheries estimation: potential approaches and solutions." ICES Journal of Marine Science 72, no. 1 (March 5, 2014): 186–93. http://dx.doi.org/10.1093/icesjms/fsu023.
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Abstract The increasingly sophisticated methods developed for stock assessment are not always suited to data-poor fisheries. Data-poor fisheries are often low in value, so the researcher time available for their assessment is also small. The dual constraints of reduced data and reduced time make stock assessments for low-value stocks particularly challenging. Prior probability distributions are useful for transferring knowledge from data-rich to data-poor fisheries. When data are limited, it is important to make the most of what few data is available. However, fully understanding potential biases in data are just as important in the data-poor context as it is in data-rich fisheries. A key aspect of stock assessment is peer review. Providing a comprehensive, yet concise, set of diagnostics is crucial to a stock assessment where time is limited. Against the standards by which data-rich stock assessments are judged, stock assessments for data-poor stocks are likely to be found deficient. A key challenge is to maintain a balance between the opposing risks of inappropriate management “action” due to assessment inaccuracy, and inappropriate management “inaction” due to assessment uncertainty.
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Arrizabalaga, Haritz, Victor R. Restrepo, Mark N. Maunder, and Jacek Majkowski. "Using stock assessment information to assess fishing capacity of tuna fisheries." ICES Journal of Marine Science 66, no. 9 (June 19, 2009): 1959–66. http://dx.doi.org/10.1093/icesjms/fsp165.
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Abstract Arrizabalaga, H., Restrepo, V. R., Maunder, M. N., and Majkowski, J. 2009. Using stock assessment information to assess fishing capacity of tuna fisheries. – ICES Journal of Marine Science, 66: 1959–1966. In tuna and tuna-like fisheries, there is a need for periodic assessments of fishing capacity to aid management. However, the nature and quantity of data needed to apply conventional methodologies for estimating fishing capacity are not usually available for tuna fisheries. We discuss simple alternative approaches to estimate fishing capacity and related quantities (i.e. capacity utilization, excess capacity, and overcapacity) directly from stock assessment inputs and outputs that are usually available for most tuna (and many other) stocks. Sensitivity analyses are performed to assess the effect of different levels of data aggregation and different assumptions made during the stock assessments on estimates of fishing capacity. Main advantages and disadvantages of the proposed methodologies are also illustrated using stock assessment information from different tuna stocks with different historical developments and trends in fishing mortality.
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Starr, Paul, John H. Annala, and Ray Hilborn. "Contested stock assessment: two case studies." Canadian Journal of Fisheries and Aquatic Sciences 55, no. 2 (February 1, 1998): 529–37. http://dx.doi.org/10.1139/f97-230.
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We describe two case studies where scientists representing alternative interest groups worked together to attempt to resolve scientific issues of fisheries assessments. In several fisheries in New Zealand, commercial fishing interests hired consultants to review governmental assessments. In some of these fisheries, the two sides provided alternative competing assessments; in other fisheries, there was a cooperative agreed-upon assessment. In the analysis of chinook salmon (Oncorhynchus tshawytscha) within the Pacific Salmon Treaty, scientists representing all parties agreed upon an assessment procedure and developed it over a number of years. Such contested assessments provide a number of benefits including (i) intense peer review, (ii) the ability to bring data from all parties into the assessment process, and (iii) better understanding and trust of the assessments by the different interest groups. Effective peer review requires repeating the calculations associated with data sources and assessment models. We suggest that contested assessments, despite the extra cost, are highly valuable, as they provide a substantially improved standard of assessment. Contested assessments will evolve towards cooperative analysis unless participating parties feel that the cooperative assessment is counter to their perceived interests.
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Fisch, Nicholas, Angela Collins, and Edward V. Camp. "What is stock assessment?" EDIS 2021, no. 2 (May 4, 2021): 5. http://dx.doi.org/10.32473/edis-fa232-2021.
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Whether you’re an angler, diver, conservationist, or just interested in fisheries, you’ve likely heard the term “stock assessment” before. What are stock assessments? How do they work? How do they inform management decisions? This publication provides information to the public and people serving in natural resource management agencies and working in outreach and Extension to show how fisheries management decisions are made.
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Conquest, Loveday L. "Stock Assessment in Inland Fisheries." Transactions of the American Fisheries Society 127, no. 1 (January 1998): 153–54. http://dx.doi.org/10.1577/1548-8659(199801)127:1<0153:sditsc>2.0.co;2.
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Medley, P. A., G. Gaudian, and S. Wells. "Coral reef fisheries stock assessment." Reviews in Fish Biology and Fisheries 3, no. 3 (September 1993): 242–85. http://dx.doi.org/10.1007/bf00043930.
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Kuparinen, Anna, Samu Mäntyniemi, Jeffrey A. Hutchings, and Sakari Kuikka. "Increasing biological realism of fisheries stock assessment: towards hierarchical Bayesian methods." Environmental Reviews 20, no. 2 (June 2012): 135–51. http://dx.doi.org/10.1139/a2012-006.
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Excessively high rates of fishing mortality have led to rapid declines of several commercially important fish stocks. To harvest fish stocks sustainably, fisheries management requires accurate information about population dynamics, but the generation of this information, known as fisheries stock assessment, traditionally relies on conservative and rather narrowly data-driven modelling approaches. To improve the information available for fisheries management, there is a demand to increase the biological realism of stock-assessment practices and to better incorporate the available biological knowledge and theory. Here, we explore the development of fisheries stock-assessment models with an aim to increasing their biological realism, and focus particular attention on the possibilities provided by the hierarchical Bayesian modelling framework and ways to develop this approach as a means of efficiently incorporating different sources of information to construct more biologically realistic stock-assessment models. The main message emerging from our review is that to be able to efficiently improve the biological realism of stock-assessment models, fisheries scientists must go beyond the traditional stock-assessment data and explore the resources available in other fields of biological research, such as ecology, life-history theory and evolutionary biology, in addition to utilizing data available from other stocks of the same or comparable species. The hierarchical Bayesian framework provides a way of formally integrating these sources of knowledge into the stock-assessment protocol and to accumulate information from multiple sources and over time.
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Duplisea, Daniel E. "Eliminating implausible fisheries assessment models using fishers’ knowledge." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 8 (August 2018): 1280–90. http://dx.doi.org/10.1139/cjfas-2017-0178.
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Peer review of competing deepwater redfish (Sebastes mentella) assessment models revealed data inconsistencies where stock biomass decline shown by the survey in the 1990s was too rapid to be explained solely by reported catch. The models invoked different techniques to achieve fits, one by changing mortality at age and the other by survey weighting. The former fitted reported catch well, while the latter accepted a mismatch between reported and estimated catch. The assessments produced different estimates of historical stock size and future productivity. Interviews conducted with fishers of the stock suggested that catch was at least twice as high as the official record. In light of the fishers’ evidence, the model that invoked a large change in mortality with age to follow reported catch closely now appears less credible. This serves as a warning against introducing new biological mechanisms without credible justification. This is an example of how indicators derived from fisher’s knowledge, even if only from a small number of interviews, can be used to eliminate less plausible models.
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Chen, Yong. "Quality of fisheries data and uncertainty in stock assessment." Scientia Marina 67, S1 (April 30, 2003): 75–87. http://dx.doi.org/10.3989/scimar.2003.67s175.
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Cadrin, Steven X., and Mark Dickey-Collas. "Stock assessment methods for sustainable fisheries." ICES Journal of Marine Science 72, no. 1 (December 19, 2014): 1–6. http://dx.doi.org/10.1093/icesjms/fsu228.
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Abstract This special volume of the ICES Journal compiles contributions from the World Conference on Stock Assessment Methods for Sustainable Fisheries (July 2013, Boston, USA). The conference was the product of a strategic initiative on stock assessment methods that engaged many national and regional fishery management organizations to assure that scientists can apply the most appropriate methods when developing management advice. An inclusive workshop was designed to evaluate the performance of a variety of model categories by applying multiple models to selected case study data as well as simulated pseudo-data that had realistic measurement error. All model applications had difficulties in recovering the simulated stock and fishing mortality trends, particularly at the end of the assessment time series, when they are most important for informing fishery management. This general result suggests that the next steps in evaluating the performance of stock assessment methods should include stock status relative to sustainable reference points, catch advice, multi-model consideration, and alternative management procedures. Recognition of the limitations of conventional stock assessment methods should promote further development of data-limited approaches, methods with time-varying parameters, or spatial complexity, and a more revolutionary shift towards the application of multispecies and ecosystem models. The contributions in this volume address methodological themes that are expected to improve the scientific basis of fishery management. Furthermore, the limitations of stock assessment methods and associated uncertainty should be more extensively considered in fishery management strategies and tactical decisions. Recommendations developed during the conference called for the establishment of a global initiative to synthesize regional advances, form guidance on best practices, promote strategic investments, and highlight research needs for fish stock assessments.
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Hoff, Ayoe, Hans Frost, Clara Ulrich, Dimitrios Damalas, Christos D. Maravelias, Leyre Goti, and Marina Santurtún. "Economic effort management in multispecies fisheries: the FcubEcon model." ICES Journal of Marine Science 67, no. 8 (June 21, 2010): 1802–10. http://dx.doi.org/10.1093/icesjms/fsq076.
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Abstract Hoff, A., Frost, H., Ulrich, C., Damalas, D., Maravelias, C. D., Goti, L., and Santurtún, M. 2010. Economic effort management in multispecies fisheries: the FcubEcon model. – ICES Journal of Marine Science, 67: 1802–1810. Applying single-species assessment and quotas in multispecies fisheries can lead to overfishing or quota underutilization, because advice can be conflicting when different stocks are caught within the same fishery. During the past decade, increased focus on this issue has resulted in the development of management tools based on fleets, fisheries, and areas, rather than on unit fish stocks. A natural consequence of this has been to consider effort rather than quota management, a final effort decision being based on fleet-harvest potential and fish-stock-preservation considerations. Effort allocation between fleets should not be based on biological considerations alone, but also on the economic behaviour of fishers, because fisheries management has a significant impact on human behaviour as well as on ecosystem development. The FcubEcon management framework for effort allocation between fleets and fisheries is presented, based on the economic optimization of a fishery's earnings while complying with stock-preservation criteria. Through case studies of two European fisheries, it is shown how fishery earnings can be increased significantly by reallocating effort between fisheries in an economically optimal manner, in both effort-management and single-quota management settings.
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Maunder, Mark N., and Kevin R. Piner. "Contemporary fisheries stock assessment: many issues still remain." ICES Journal of Marine Science 72, no. 1 (February 25, 2014): 7–18. http://dx.doi.org/10.1093/icesjms/fsu015.
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Abstract Interpretation of data used in fisheries assessment and management requires knowledge of population (e.g. growth, natural mortality, and recruitment), fisheries (e.g. selectivity), and sampling processes. Without this knowledge, assumptions need to be made, either implicitly or explicitly based on the methods used. Incorrect assumptions can have a substantial impact on stock assessment results and management advice. Unfortunately, there is a lack of understanding of these processes for most, if not all, stocks and even for processes that have traditionally been assumed to be well understood (e.g. growth and selectivity). We use information content of typical fisheries data that is informative about absolute abundance to illustrate some of the main issues in fisheries stock assessment. We concentrate on information about absolute abundance from indices of relative abundance combined with catch, and age and length-composition data and how the information depends on knowledge of population, fishing, and sampling processes. We also illustrate two recently developed diagnostic methods that can be used to evaluate the absolute abundance information content of the data. Finally, we discuss some of the reasons for the slowness of progress in fisheries stock assessment.
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Anderson, Sean C., Trevor A. Branch, Daniel Ricard, and Heike K. Lotze. "Assessing global marine fishery status with a revised dynamic catch-based method and stock-assessment reference points." ICES Journal of Marine Science 69, no. 8 (June 17, 2012): 1491–500. http://dx.doi.org/10.1093/icesjms/fss105.
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Abstract Anderson, S. C., Branch, T. A., Ricard, D., and Lotze, H. K. 2012. Assessing global marine fishery status with a revised dynamic catch-based method and stock-assessment reference points. – ICES Journal of Marine Science, 69: . The assessment of fishery status is essential for management, yet fishery-independent estimates of abundance are lacking for most fisheries. Methods exist to infer fishery status from catches, but the most commonly used method is biased towards classifying fisheries as overexploited or collapsed through time and does not account for still-developing fisheries. We introduce a revised method that overcomes these deficiencies by smoothing catch series iteratively, declaring fisheries developing within three years of peak catch, and calibrating thresholds to biological reference points. Compared with status obtained from stock-assessment reference points for 210 stocks, our approach provides a more realistic assessment than the original method, but cannot be perfect because catches are influenced by factors other than biomass. Applied to FAO catches, our method suggests in 2006 32% of global fisheries were developing, 27% fully exploited, 25% overexploited, and 16% collapsed or closed. Although less dire than previous assessments, this still indicates substantial numbers of overexploited stocks. Probably because median exploitation rate decreased since 1992, our catch-based results do not reflect recent stabilization of assessed-stock biomass. Whether this outlook also applies to unassessed stocks can only be revealed with increased or more representative collection of biomass- and exploitation-rate trends.
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Lindegren, Martin, Staffan Waldo, P. Anders Nilsson, Henrik Svedäng, and Anders Persson. "Towards sustainable fisheries of the Öresund cod (Gadus morhua) through sub-stock-specific assessment and management recommendations." ICES Journal of Marine Science 70, no. 6 (May 12, 2013): 1140–50. http://dx.doi.org/10.1093/icesjms/fst042.
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Abstract Lindegren, M., Waldo, S., Nilsson, P. A., Svedäng, H., and Persson, A. 2013. Towards sustainable fisheries of the Öresund cod (Gadus morhua) through sub-stock-specific assessment and management recommendations. – ICES Journal of Marine Science, 70: 1140–1150. Fisheries management traditionally relies on stock assessments assuming discrete populations within large administrational areas. However, failing to account for sub-stock structuring may result in overestimation of the stocks' true harvest potential and unsustainable exploitation of small stock elements. Atlantic cod (Gadus morhua) frequently occurs in spatially segregated populations, some of which exhibit fine-scaled stock structuring within current management boundaries. Here we use the locally spawning cod stock in the Sound (“Öresund”) as a case study, and perform a sub-stock-specific assessment to evaluate biological and economic effects of managing the Sound cod as a separate stock. Our results indicate that reducing exploitation pressure, particularly through technical regulations i.e. increasing gill-net mesh sizes, would not only enhance the stock age distribution, but yield long-term net benefits to the local gill-net fishery. Furthermore, our study emphasizes the need for developing sub-stock-specific management recommendations in order to ensure the maintenance of fisheries resources in general, and the persistence of sub-stock structuring in particular.
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Prestes, Luiza, Fabiana Calacina da Cunha, Maria Gercilia Mota Soares, Marcos Sidney Brito Oliveira, Netie Izabel Oliveira, and Alexandro Cezar Florentino. "Stock Assessment: Sustainable management in high and medium Araguari River, Amapá, Brazil." Ciência e Natura 42 (June 29, 2020): e71. http://dx.doi.org/10.5902/2179460x40186.
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Fisheries in Araguari river is an alternative income for families that depend on exploitation of natural resources. This study evaluates fisheries production in high and medium Araguari river to determine the bioeconomic reference points of fishery activities. Logbooks of fisheries were used from Fishermen Colony Z-16 from 2003 to 2010. The Maximum Sustainable Yield (MSY) and Effort at Maximum Sustainable Yield (fmsy) was: MSYSchaefer = 11246 kg and fmsy = 754 fisheries/year, and MSYFox = 11478 kg and fmsy = 1214 fisheries/year and at Bioeconomic Equilibrium (Eebe) Eebe = 10712 kg and Effort at Bioeconomic Equilibrium (febe) febe = 918 fisheries/year. The status of fisheries from Araguari River was declared as overfishing and in this study, we found the same results. The Maximum Economic Yield (MEY) was reached too, as the fisheries were at Bioeconomic Equilibrium (EBE). The fishery mortality (Fyear/Fmsy) and fishery effort (fyear/fmsy) trends show that from 2003 to 2009 the values were sustainable. In 2010 those trends became unsustainable, and the Maximum Economic Yield (MEY) for all years is unsustainable too. It is required this study be considered in future management agreements.
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Jamnia, Abdul Rashid, Ahmad Ali Keikha, Mahmoud Ahmadpour, Abdoul Ahad Cissé, and Mohammad Rokouei. "Applying bayesian population assessment models to artisanal, multispecies fisheries in the Northern Mokran Sea, Iran." Nature Conservation 28 (August 13, 2018): 61–89. http://dx.doi.org/10.3897/natureconservation.28.25212.
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Small-scale fisheries substantially contribute to the reduction of poverty, local economies and food safety in many countries. However, limited and low-quality catches and effort data for small-scale fisheries complicate the stock assessment and management. Bayesian modelling has been advocated when assessing fisheries with limited data. Specifically, Bayesian models can incorporate information of the multiple sources, improve precision in the stock assessments and provide specific levels of uncertainty for estimating the relevant parameters. In this study, therefore, the state-space Bayesian generalised surplus production models will be used in order to estimate the stock status of fourteen Demersal fish species targeted by small-scale fisheries in Sistan and Baluchestan, Iran. The model was estimated using Markov chain Monte Carlo (MCMC) and Gibbs Sampling. Model parameter estimates were evaluated by the formal convergence and stationarity diagnostic tests, indicating convergence and accuracy. They were also aligned with existing parameter estimates for fourteen species of the other locations. This suggests model reliability and demonstrates the utility of Bayesian models. According to estimated fisheries’ management reference points, all assessed fish stocks appear to be overfished. Overfishing considered, the current fisheries management strategies for the small-scale fisheries may need some adjustments to warrant the long-term viability of the fisheries.
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Beacham, Terry D., Kim Jonsen, Brenda McIntosh, Ben J. G. Sutherland, David Willis, Cheryl Lynch, and Colin Wallace. "Large-scale parentage-based tagging and genetic stock identification applied in assessing mixed-stock fisheries and hatchery brood stocks for coho salmon in British Columbia, Canada." Canadian Journal of Fisheries and Aquatic Sciences 77, no. 9 (September 2020): 1505–17. http://dx.doi.org/10.1139/cjfas-2020-0035.
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Direct DNA sequencing is powering a revolution in the application of genetics to resource management, with parentage-based tagging (PBT) increasingly applied to salmon fisheries and hatchery brood stock management and assessment. Genetic stock identification (GSI) and PBT were applied to assessment of 2018 coho salmon (Oncorhynchus kisutch) ocean fisheries and hatchery brood stocks in British Columbia (BC), Canada, with 6391 individuals successfully genotyped in fishery samples and 7805 individuals genotyped in 40 hatchery brood stocks. Population-specific contributions to mixed-stock fisheries and exploitation rates were estimated with coded-wire tags (CWTs) and GSI–PBT technologies for six populations. PBT assignments, verified by CWTs, were 100% accurate for 308 individuals with respect to population of origin and age. There was generally reasonably close agreement of estimated population-specific exploitation rates between CWT and genetic methods. We conclude that a genetic approach can improve upon the results available from the current CWT program for assessment and management of coho salmon fisheries and hatchery brood stocks in BC and provide information critical to aid in implementation of Canada’s Policy for Conservation of Wild Pacific Salmon.
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GUAN, Wenjiang, Siquan TIAN, Jiangfeng ZHU, and Xinjun CHEN. "A review of fisheries stock assessment models." Journal of Fishery Sciences of China 20, no. 5 (December 16, 2013): 1112–20. http://dx.doi.org/10.3724/sp.j.1118.2013.01112.
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Hammond, T. R., and V. M. Trenkel. "Censored catch data in fisheries stock assessment." ICES Journal of Marine Science 62, no. 6 (January 1, 2005): 1118–30. http://dx.doi.org/10.1016/j.icesjms.2005.04.015.
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Abstract Landings statistics can be lower than true catches because many fish are discarded or landed illegally. Since many discards do not survive, treating landings as true catches can lead to biased stock assessments. This paper proposes treating catch as censored by bounding it below by the landings, L, and above by cL (for scalar c > 1). We demonstrate the approach with a simulation study, using a Schaefer surplus production model. Parameters were estimated in a Bayesian framework with BUGS software using two sets of priors. Both the traditional true-catch method and a survey-and-effort method (which was landings free) performed worse on average than the censored approach, as measured by the Bayes risk associated with estimates of maximum sustainable yield (MSY) and of an index of depletion (X). Recursive partitioning (regression trees) was used to associate simulation parameters to best-performing methods, showing that higher commercial fish catchability favoured the censored method at estimating X. In conclusion, censored methods provide a means of dealing with discarding and misreporting that can outperform some traditional alternatives.
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Pierce, Graham J., and Angel Guerra. "Stock assessment methods used for cephalopod fisheries." Fisheries Research 21, no. 1-2 (December 1994): 255–85. http://dx.doi.org/10.1016/0165-7836(94)90108-2.
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Smith, Michael T., and Julian T. Addison. "Methods for stock assessment of crustacean fisheries." Fisheries Research 65, no. 1-3 (December 2003): 231–56. http://dx.doi.org/10.1016/j.fishres.2003.09.017.
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Stewart, Ian J., and Steven J. D. Martell. "Reconciling stock assessment paradigms to better inform fisheries management." ICES Journal of Marine Science 72, no. 8 (April 12, 2015): 2187–96. http://dx.doi.org/10.1093/icesjms/fsv061.
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Abstract For several decades, the fisheries stock assessment paradigms of virtual population analysis (VPA) and statistical catch-at-age (SCA) models have been routinely applied to major fish stocks, and their prevalence often dictated by historical continuity, local experience, and geographical differences in standard practices. Similarly, there is a growing split among models using short and long time-series. In one approach, only the recent time-series, where the data are relatively complete, and the assumptions about stationarity in population and sampling processes are relatively simple, are included. In the other, long time-series include far more historical data, but necessitate the relaxation of many common assumptions regarding stationarity. Unlike scientific paradigms in fields outside of fisheries science where empirical validation can provide a growing body of irrefutable evidence (such as physics), there is no expectation that some “truth” will emerge or that a single best stock assessment modelling approach will ultimately displace the others. The 2013 Pacific halibut SCA stock assessment, with the addition of a VPA-based analysis, is used to illustrate how an ensemble approach can represent a more complete description of the uncertainty in management quantities, relative to selecting just one of these competing model paradigms. We suggest that risk assessment for fisheries management, based on stock assessment models, should seek to avoid binary decisions about which models to include, and instead seek better approaches to incorporate alternative models. The ensemble approach to stock assessment also provides a conceptual link between traditional “best model” analyses and fully developed management strategy evaluation of harvest policy and management procedures.
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Mahon, R. "Does fisheries science serve the needs of managers of small stocks in developing countries." Canadian Journal of Fisheries and Aquatic Sciences 54, no. 9 (September 1, 1997): 2207–13. http://dx.doi.org/10.1139/f97-112.
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Despite the prevalence and socioeconomic importance of small, low total-revenue stocks, predominantly in tropical, developing countries, most of the world's fishery science effort has been devoted to large stocks. Methods for assessing and managing large stocks, though applicable to small ones, are seldom feasible for them. Minimal attention has been paid to approaches that are specifically for small stocks. The tendency for managers of fisheries on small stocks in developing countries to believe that stock assessment is essential for successful fishery management, often leads to disproportionate allocation of resources to stock assessment rather than other critical components of management. This has been reinforced by several agencies that have made stock assessment methods and software available for use in developing countries, while paying little attention to other dimensions of fishery assessment and management. Hence, management efforts for small stocks are often stock assessment driven (SAD), rather than management objective driven (MOD), as they should be. The sequence of actions typical of these two approaches is contrasted. Managers of small stocks in developing countries need international programs that will develop and promote formal methodological approaches with broad emphasis on management objectives and process.
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Guan, Lisha, Yong Chen, Robert Boenish, Xianshi Jin, and Xiujuan Shan. "Improving data-limited stock assessment with sporadic stock index information in stock reduction analysis." Canadian Journal of Fisheries and Aquatic Sciences 77, no. 5 (May 2020): 857–68. http://dx.doi.org/10.1139/cjfas-2018-0500.
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As most exploited fisheries lack a coherent time series of biomass index, development of data-limited stock assessment methods such as stock reduction analysis (SRA), is critical for fishery stock assessment due to their modest data requirements for estimating stock status and overfishing catch limits. In this study, we propose that sporadic time series of biomass indices, if available, may be fully utilized to inform priors of recent relative biomass (BT/B1) for data-limited stocks. We evaluated the performance of SRA incorporating this index-based prior by comparing two other common SRA priors (a deterministic prior set at 40% of the unfished biomass and a catch-based prior) with estimates from the likelihood-based assessments of 91 fish stocks from the RAM Legacy database. We extended our analysis by evaluating performance based on life history attributes and two depletion levels with BT/BMSY equaling 1 as the breakpoint. Results suggest index-based priors enhance accuracy for fish stocks at both depletion levels. We demonstrate that performance of SRA can be affected by three factors: the reliability of priors for BT/B1, recent depletion level, and life history.
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Thorson, James T., Trevor A. Branch, and Olaf P. Jensen. "Using model-based inference to evaluate global fisheries status from landings, location, and life history data." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 4 (April 2012): 645–55. http://dx.doi.org/10.1139/f2012-016.
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Assessing fishery collapses worldwide is hindered by the lack of biomass data for most stocks, leading to the use of landings-based proxies or the assumption that existing stock assessments are globally representative. We argue that the use of sparse assessments to evaluate fishery status requires model-based inference because assessment availability varies spatially and temporally, and we derive a model that extrapolates from assessment results to available landings, life history, and location data. This model uses logistic regression to classify stocks into different prediction bins and estimates the probability of collapse in each using cross-validation. Results show that landings, life history, and location are informative to discriminate among different probabilities of collapse. We find little evidence that regions with fewer assessments have a greater proportion of collapsed stocks, while acknowledging weak inferential support regarding regions with one or fewer assessments. Our extrapolation suggests that 4.5%–6.5% of stocks defined by landings data are collapsed, but that this proportion is increasing. Finally, we propose a research agenda that combines stock assessment and landings databases while overcoming limitations in each.
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Albertsen, Christoffer Moesgaard, Anders Nielsen, and Uffe Høgsbro Thygesen. "Connecting single-stock assessment models through correlated survival." ICES Journal of Marine Science 75, no. 1 (August 1, 2017): 235–44. http://dx.doi.org/10.1093/icesjms/fsx114.
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Abstract Fisheries management is mainly conducted via single-stock assessment models assuming that fish stocks do not interact, except through assumed natural mortalities. Currently, the main alternative is complex ecosystem models which require extensive data, are difficult to calibrate, and have long run times. We propose a simple alternative. In three case studies each with two stocks, we improve the single-stock models, as measured by Akaike information criterion, by adding correlation in the cohort survival. To limit the number of parameters, the correlations are parameterized through the corresponding partial correlations. We consider six models where the partial correlation matrix between stocks follows a band structure ranging from independent assessments to complex correlation structures. Further, a simulation study illustrates the importance of handling correlated data sufficiently by investigating the coverage of confidence intervals for estimated fishing mortality. The results presented will allow managers to evaluate stock statuses based on a more accurate evaluation of model output uncertainty. The methods are directly implementable for stocks with an analytical assessment and do not require any new data sources.
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Michielsens, Catherine G. J., Murdoch K. McAllister, Sakari Kuikka, Samu Mäntyniemi, Atso Romakkaniemi, Tapani Pakarinen, Lars Karlsson, and Laura Uusitalo. "Combining multiple Bayesian data analyses in a sequential framework for quantitative fisheries stock assessment." Canadian Journal of Fisheries and Aquatic Sciences 65, no. 5 (May 1, 2008): 962–74. http://dx.doi.org/10.1139/f08-015.
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This paper presents a sequential Bayesian framework for quantitative fisheries stock assessment that relies on a wide range of fisheries-dependent and -independent data and information. The presented methodology combines information from multiple Bayesian data analyses through the incorporation of the joint posterior probability density functions (pdfs) in subsequent analyses, either as informative prior pdfs or as additional likelihood contributions. Different practical strategies are presented for minimising any loss of information between analyses. Using this methodology, the final stock assessment model used for the provision of the management advice can be kept relatively simple, despite the dependence on a large variety of data and other information. This methodology is illustrated for the assessment of the mixed-stock fishery for four wild Atlantic salmon (Salmo salar) stocks in the northern Baltic Sea. The incorporation of different data and information results in a considerable update of previously available smolt abundance and smolt production capacity estimates by substantially reducing the associated uncertainty. The methodology also allows, for the first time, the estimation of stock–recruit functions for the different salmon stocks.
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Morgan, Jess A. T., Wayne D. Sumpton, Andrew T. Jones, Alexander B. Campbell, John Stewart, Paul Hamer, and Jennifer R. Ovenden. "Assessment of genetic structure among Australian east coast populations of snapper Chrysophrys auratus (Sparidae)." Marine and Freshwater Research 70, no. 7 (2019): 964. http://dx.doi.org/10.1071/mf18146.
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Snapper Chrysophrys auratus is a high-value food fish in Australia targeted by both commercial and recreational fisheries. Along the east coast of Australia, fisheries are managed under four state jurisdictions (Queensland, Qld; New South Wales, NSW; Victoria, Vic.; and Tasmania, Tas.), each applying different regulations, although it is thought that the fisheries target the same biological stock. An allozyme-based study in the mid-1990s identified a weak genetic disjunction north of Sydney (NSW) questioning the single-stock hypothesis. This study, focused on east-coast C. auratus, used nine microsatellite markers to assess the validity of the allozyme break and investigated whether genetic structure exists further south. Nine locations were sampled spanning four states and over 2000km, including sites north and south of the proposed allozyme disjunction. Analyses confirmed the presence of two distinct biological stocks along the east coast, with a region of genetic overlap around Eden in southern NSW, ~400km south of the allozyme disjunction. The findings indicate that C. auratus off Vic. and Tas. are distinct from those in Qld and NSW. For the purpose of stock assessment and management, the results indicate that Qld and NSW fisheries are targeting a single biological stock.A
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Cordue, Patrick L. "Designing optimal estimators for fish stock assessment." Canadian Journal of Fisheries and Aquatic Sciences 55, no. 2 (February 1, 1998): 376–86. http://dx.doi.org/10.1139/f97-228.
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Many estimation procedures are used in the provision of fisheries stock assessment advice. Most procedures use estimators that have optimal large-sample characteristics, but these are often applied to small-sample data sets. In this paper, a minimum integrated average expected loss (MIAEL) estimation procedure is presented. By its design a MIAEL estimator has optimal characteristics for the type of data it is applied to, given that the model assumptions of the particular problem are satisfied. The estimation procedure is developed within a decision-theoretic framework and illustrated with a Bernoulli and a fisheries example. MIAEL estimation is related to optimal Bayes estimation, as both procedures seek an estimator that minimizes an integrated loss function. In most fisheries applications a global MIAEL estimator will be difficult to determine, and a MIAEL estimator will need to be found within a given class of estimators. "Squared f-error," a generalization of the common squared error loss function is defined. It is shown that an estimator can be improved (for a given squared f-error loss function) by using its best linear transformation which is the MIAEL estimator within the class of linear transformations (in f space).
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Lorenzen, Kai. "Population dynamics and potential of fisheries stock enhancement: practical theory for assessment and policy analysis." Philosophical Transactions of the Royal Society B: Biological Sciences 360, no. 1453 (January 28, 2005): 171–89. http://dx.doi.org/10.1098/rstb.2004.1570.
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The population dynamics of fisheries stock enhancement, and its potential for generating benefits over and above those obtainable from optimal exploitation of wild stocks alone are poorly understood and highly controversial. I review pertinent knowledge of fish population biology, and extend the dynamic pool theory of fishing to stock enhancement by unpacking recruitment, incorporating regulation in the recruited stock, and accounting for biological differences between wild and hatchery fish. I then analyse the dynamics of stock enhancement and its potential role in fisheries management, using the candidate stock of North Sea sole as an example and considering economic as well as biological criteria. Enhancement through release of recruits or advanced juveniles is predicted to increase total yield and stock abundance, but reduce abundance of the naturally recruited stock component through compensatory responses or overfishing. Economic feasibility of enhancement is subject to strong constraints, including trade–offs between the costs of fishing and hatchery releases. Costs of hatchery fish strongly influence optimal policy, which may range from no enhancement at high cost to high levels of stocking and fishing effort at low cost. Release of genetically maladapted fish reduces the effectiveness of enhancement, and is most detrimental overall if fitness of hatchery fish is only moderately compromised. As a temporary measure for the rebuilding of depleted stocks, enhancement cannot substitute for effort limitation, and is advantageous as an auxiliary measure only if the population has been reduced to a very low proportion of its unexploited biomass. Quantitative analysis of population dynamics is central to the responsible use of stock enhancement in fisheries management, and the necessary tools are available.
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Bross, C. A. R. "Stock assessment and risk in South African fisheries." South African Journal of Marine Science 5, no. 1 (June 1, 1987): 919–23. http://dx.doi.org/10.2989/025776187784522720.
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Francis, R. I. C. Chris. "Data weighting in statistical fisheries stock assessment models." Canadian Journal of Fisheries and Aquatic Sciences 68, no. 6 (June 2011): 1124–38. http://dx.doi.org/10.1139/f2011-025.
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The conclusions drawn from fisheries stock assessment models can depend strongly on the relative weights assigned to different data sets. However, there is no consensus amongst practitioners as to the best approach to data weighting. From a discussion of some key questions concerning data weighting in stock assessment models, I draw three guiding principles: (i) do not let other data stop the model from fitting abundance data well; (ii) when weighting age or length composition data, allow for correlations; and (iii) do not down-weight abundance data because they may be unrepresentative. I propose an approach to data weighting based on these principles. Two factors that complicate this approach are that some decisions are inevitably subjective (which underlines the need for expert knowledge in stock assessment), and some technical problems are unresolved.
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Chen, Yong, Yan Jiao, Chi-Lu Sun, and Xinjun Chen. "Calibrating virtual population analysis for fisheries stock assessment." Aquatic Living Resources 21, no. 2 (April 2008): 89–97. http://dx.doi.org/10.1051/alr:2008030.
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Chen, Yong, Liqiao Chen, and K. I. Stergiou. "Impacts of data quantity on fisheries stock assessment." Aquatic Sciences - Research Across Boundaries 65, no. 1 (March 1, 2003): 92–98. http://dx.doi.org/10.1007/s000270300008.
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Francis, R. I. C. Chris. "Revisiting data weighting in fisheries stock assessment models." Fisheries Research 192 (August 2017): 5–15. http://dx.doi.org/10.1016/j.fishres.2016.06.006.
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Johnson, Samuel D. N., and Sean P. Cox. "Evaluating the role of data quality when sharing information in hierarchical multistock assessment models, with an application to Dover sole." Canadian Journal of Fisheries and Aquatic Sciences 76, no. 10 (October 2019): 1819–35. http://dx.doi.org/10.1139/cjfas-2018-0048.
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An emerging approach to data-limited fisheries stock assessment uses hierarchical multistock assessment models to group stocks together, sharing information from data-rich to data-poor stocks. In this paper, we simulate data-rich and data-poor fishery and survey data scenarios for a complex of Dover sole (Microstomus pacificus) stocks. Simulated data for individual stocks were used to compare estimation performance for single-stock and hierarchical multistock versions of a Schaefer production model. The single-stock and best-performing multistock models were then used in stock assessments for the real Dover sole data. Multistock models often had lower estimation errors than single-stock models when assessment data had low statistical power. Relative errors for productivity and relative biomass parameters were lower for multistock assessment model configurations. In addition, multistock models that estimated hierarchical priors for survey catchability performed the best under data-poor scenarios. We conclude that hierarchical multistock assessment models are useful for data-limited stocks and could provide a more flexible alternative to data pooling and catch-only methods; however, these models are subject to nonlinear side effects of parameter shrinkage. Therefore, we recommend testing hierarchical multistock models in closed-loop simulations before application to real fishery management systems.
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Eero, Margit, Harry V. Strehlow, Charles M. Adams, and Morten Vinther. "Does recreational catch impact the TAC for commercial fisheries?" ICES Journal of Marine Science 72, no. 2 (July 14, 2014): 450–57. http://dx.doi.org/10.1093/icesjms/fsu121.
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Abstract The western Baltic cod is one of the first fish stocks in Europe that, since 2013, includes recreational catches in stock assessment and fisheries management advice. In this paper, we investigate the sensitivity of the calculated commercial total allowable catch (TAC) to including recreational catches in stock assessment. Our results show that the most crucial aspect in terms of the impact on commercial TAC is the assumption on recreational catch dynamics relative to that of commercial fisheries used in forecast. The results were less sensitive to the information on the historical amount and age structure of recreational catch. Our study is intended to inform potential debates related to resource allocation between the commercial and recreational sectors and contribute to developing a general framework for incorporating recreational catches in fisheries management advice in ICES.
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Kleiber, Pierre, Michael G. Hinton, and Yuji Uozumi. "Stock assessment of blue marlin (Makaira nigricans) in the Pacific using MULTIFAN-CL." Marine and Freshwater Research 54, no. 4 (2003): 349. http://dx.doi.org/10.1071/mf01246.
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In the Pacific, blue marlin are an incidental catch of longline fisheries and an important resource for big game recreational fishing. Over the past two decades, blue marlin assessments by different techniques have yielded results ranging from an indication of declining stock to a state of sustained yield at approximately the maximum average level. Longline fishing practices have changed over the years since the 1950s in response to changes in principal target species and to gear developments. Despite increasingly sophisticated attempts to standardize fishing effort with changing fishing practices, the stock assessments to date are likely confounded to a greater or lesser degree by changes in catchability for blue marlin. Yet, only data from commercial longline fisheries targeting tuna provide sufficient spatial and temporal coverage to allow assessment of this resource. To re-assess the blue marlin stocks in the Pacific and also to assess the efficacy of a habitat-based standardization of longline effort, a collaborative analysis was conducted involving scientists at the National Research Institute of Far Seas Fisheries, Shimizu, Japan, the Inter-American Tropical Tuna Commission, La Jolla, California, and the NOAA Fisheries Honolulu Laboratory, Honolulu, Hawaii. Using MULTIFAN-CL as an assessment tool, there was considerable uncertainty in quantifying the fishing effort levels that would produce a maximum sustainable yield. However, it was found that, at worst, blue marlin in the Pacific are close to a fully exploited state, that is the population and the fishery are somewhere near the top of the yield curve. Furthermore, it was found that effort standardization using a habitat-based model allowed estimation of parameters within reasonable bounds and with reduced confidence intervals about those values.
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Monnahan, Cole C., Trevor A. Branch, James T. Thorson, Ian J. Stewart, and Cody S. Szuwalski. "Overcoming long Bayesian run times in integrated fisheries stock assessments." ICES Journal of Marine Science 76, no. 6 (April 21, 2019): 1477–88. http://dx.doi.org/10.1093/icesjms/fsz059.
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Abstract Bayesian inference is an appealing alternative to maximum likelihood estimation, but estimation can be prohibitively long for integrated fisheries stock assessments. Here, we investigated potential causes of long run times including high dimensionality, complex model structure, and inefficient Bayesian algorithms for four US assessments written in AD Model Builder (ADMB), both custom built and Stock Synthesis models. The biggest culprit for long run times was overparameterization and they were reduced from months to days by adding priors and turning off estimation for poorly-informed parameters (i.e. regularization), especially for selectivity parameters. Thus, regularization is a necessary step in converting assessments from frequentist to Bayesian frameworks. We also tested the usefulness of the no-U-turn sampler (NUTS), a Bayesian algorithm recently added to ADMB, and the R package adnuts that allows for easy implementation of NUTS and parallel computation. These additions further reduced run times and better sampled posterior distributions than existing Bayesian algorithms in ADMB, and for both of these reasons we recommend using NUTS for inference. Between regularization, a faster algorithm, and parallel computation, we expect models to run 50–50 000 times faster for most current stock assessment models, opening the door to routine usage of Bayesian methods for management of fish stocks.
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Geromont, H. F., and D. S. Butterworth. "Complex assessments or simple management procedures for efficient fisheries management: a comparative study." ICES Journal of Marine Science 72, no. 1 (February 26, 2014): 262–74. http://dx.doi.org/10.1093/icesjms/fsu017.
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Abstract Complex stock assessment methods are data- and expertise-hungry, with the annual updates of catch-at-age data and models typically seen as an essential requirement for sound management. But are the heavy commitments of resources required for this level of annual intervention really necessary to achieve efficient long-term fishery management? This question is addressed through a retrospective analysis of management performance over the last 20 years for four North Atlantic fish stocks. The assessments for two of these stocks have exhibited fairly strong retrospective patterns. The actual assessment advice for these stocks was provided based on complex assessment methods making use of age data. The outcomes are compared with what could have been achieved with much simpler catch control rules based upon age-aggregated survey indices alone. Even for the stocks whose assessments exhibit retrospective patterns, these simple rules can achieve virtually equivalent catch and risk performance, with much less interannual TAC variability, compared with what actually occurred over the past 20 years.
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Drouineau, Hilaire, Louise Savard, Mathieu Desgagnés, and Daniel Duplisea. "SPAM (Sex-Structured Pandalus Assessment Model): a stock assessment model for Pandalus stocks." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 4 (April 2012): 770–83. http://dx.doi.org/10.1139/f2012-011.
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Despite the economic importance of Pandalus shrimp fisheries, few analytical tools have been developed to assess their stocks, and traditional stock assessment models are not appropriate because of biological specificities of Pandalus species. In this context, we propose SPAM (Sex-Structured Pandalus Assessment Model), a model dedicated to protandric hermaphrodite pandalids stock assessment. Pandalids are difficult to assess because the cues affecting sex change, size at recruitment, and mortality variability are not well understood or characterized. The novel structure of the model makes it possible to adequately describe variability in natural mortality by stage and in time, as well as variability in size at sex change and recruitment. The model provides traditional stock assessment outputs, such as fishing mortality estimates and numbers of individuals, and provides in addition yearly natural mortality estimates. The model is applied to the exploited shrimp stock of Pandalus borealis in Sept-Îles (Québec, Canada) as an illustrative example of the utility of the approach.
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Kanaiwa, Minoru, Yong Chen, and Carl Wilson. "Evaluating a seasonal, sex-specific size-structured stock assessment model for the American lobster, Homarus americanus." Marine and Freshwater Research 59, no. 1 (2008): 41. http://dx.doi.org/10.1071/mf07121.
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Many models of different complexities are developed for fisheries stock assessment, and yet few have been rigorously evaluated for their performance in capturing fisheries population dynamics. This causes confusion about when a model should be used or not in assessing fisheries resources. This is especially true for models with complex structures. The present study evaluated the performance of a seasonal, sex-specific and size-structured stock assessment model with respect to the temporal pattern of recruitment, observation errors associated with input data, process errors and violation of model assumptions for the American lobster Homarus americanus. Using an individual-based lobster simulator, a series of lobster fisheries with different characteristics were simulated and the model was applied to the simulated data to estimate key fisheries parameters. Estimated values were then compared with the true values in the simulated fisheries to evaluate the model’s ability to capture the temporal trend in stock abundance, biomass and recruitment, and to identify factors that might result in model failure. Results show that this newly developed lobster stock assessment model performs well in capturing the dynamics of the lobster population under a wide range of conditions. Temporal trends in natural mortality and biased estimates of growth parameters posed the most serious problems. The present study shows the importance of model evaluation.
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Goethel, Daniel R., Christopher M. Legault, and Steven X. Cadrin. "Demonstration of a spatially explicit, tag-integrated stock assessment model with application to three interconnected stocks of yellowtail flounder off of New England." ICES Journal of Marine Science 72, no. 1 (February 20, 2014): 164–77. http://dx.doi.org/10.1093/icesjms/fsu014.
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Abstract Ignoring population structure and connectivity in stock assessment models can introduce bias into important management metrics. Tag-integrated assessment models can account for spatially explicit population dynamics by modelling multiple population components, each with unique demographics, and estimating movement among them. A tagging submodel is included to calculate predicted tag recaptures, and observed tagging data are incorporated in the objective function to inform estimates of movement and mortality. We describe the tag-integrated assessment framework and demonstrate its use through an application to three stocks of yellowtail flounder (Limanda ferruginea) off New England. Movement among the three yellowtail flounder stocks has been proposed as a potential source of uncertainty in the closed population assessments of each. A tagging study was conducted during 2003–2006 with over 45 000 tagged fish released in the region, and the tagging data were included in the tag-integrated model. Results indicated that movement among stocks was low, estimates of stock size and fishing mortality were similar to those from conventional stock assessments, and incorporating stock connectivity did not resolve residual patterns. Despite low movement estimates, new interpretations of regional stock dynamics may have important implications for regional fisheries management given the source-sink nature of movement estimates.
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Anderson, Sean C., Cole C. Monnahan, Kelli F. Johnson, Kotaro Ono, and Juan L. Valero. "ss3sim: An R Package for Fisheries Stock Assessment Simulation with Stock Synthesis." PLoS ONE 9, no. 4 (April 3, 2014): e92725. http://dx.doi.org/10.1371/journal.pone.0092725.
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Sherman, Kenneth. "Sustaining the world's large marine ecosystems." ICES Journal of Marine Science 72, no. 9 (September 15, 2015): 2521–31. http://dx.doi.org/10.1093/icesjms/fsv136.
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Abstract In this essay, I review nearly six decades of a career in marine science and fisheries considering scientific contributions, successes, failures, and changes in my field of practice. My body of work has been in plankton research to support fisheries assessments, and in ecosystems programme development and implementation. I describe my early studies on Pacific plankton oceanography in relation to fisheries assessment, and subsequent studies of plankton oceanography and fisheries in relation to coastal ocean fisheries and management. Early in my career, realizing that applications of my published results and those of other fisheries ecologists were generally not included in fish stock assessments, I participated in a national planning group that introduced a system for marine resources monitoring, assessment, and prediction (MARMAP) that included primary productivity, ichthyoplankton, zooplankton, and oceanographic assessments as important components for large-scale fisheries ecology assessment. I joined with European colleagues in ICES to advance fisheries ecology studies in fish stock assessments in the 1970s and 1980s. In 1983, I conceived with Professor Lewis Alexander of the University of Rhode Island a system for assessing and managing marine resources within the spatial domain of ecologically delineated large marine ecosystems (LMEs). On behalf of the National Oceanic and Atmospheric Administration, and in partnership with developing countries, international financial organizations, UN agencies, and NGOs, I am currently contributing scientific and technical advice to a global network of assessment and management projects in 22 LMEs with 110 developing countries and $3.1 billion in financial support. The participating countries are applying a modular framework of natural science and social science indicators for assessing the changing states of LMEs. I conclude the essay with a retrospective viewpoint on my career and changes over half a century of practicing the application of marine science in relation to sustaining the goods and services of the ocean Commons.
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Baelde, Pascale. "Fishers' description of changes in fishing gear and fishing practices in the Australian South East Trawl Fishery." Marine and Freshwater Research 52, no. 4 (2001): 411. http://dx.doi.org/10.1071/mf99149.
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Between the mid 1980s and early 1990s, the concurrence of three major events significantly altered the structure and dynamics of the demersal trawl sector in the Australian South-East Fishery (SEF). These events included marked technological improvement, severe decline of major fish stocks and introduction of an Individual Transferable Quota system. They have led to a switch from maximizing catch volume to maximizing catch composition and quotas, with important associated changes in fishing practices and catches. To better understand these changes and their effect on stock assessment and management, an industry survey asked SEF trawl fishers to describe their fishing gear and fishing practices in detail. This paper is a qualitative synthesis of current trends in fishing that most significantly affect the single-species, logbook-dependent assessment and management of the fishery. It demonstrates how effective collaboration between scientists and fishers can benefit fisheries research and management, by helping scientists make more informed analysis and interpretations of fisheries data.
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Ba, Kamarel, Modou Thiaw, Massal Fall, Ndiaga Thiam, Beyah Meissa, Didier Jouffre, Omar Thiom Thiaw, and Didier Gascuel. "Long-term fishing impact on the Senegalese coastal demersal resources: diagnosing from stock assessment models." Aquatic Living Resources 31 (2018): 8. http://dx.doi.org/10.1051/alr/2017046.
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For the first time in Senegal, assessments based on both stochastic and deterministic production models were used to draw a global diagnosis of the fishing impact on coastal demersal stocks. Based one national fisheries databases and scientific trawl surveys data: (i) trends in landings since 1971 were examined, (ii) abundance indices of 10 stocks were estimated using linear models fitted to surveys data and commercial catch per unit efforts, and (iii) stock assessments were carried out using pseudo-equilibrium Fox and Pella-Tomlinson models and a Biomass dynamic production model fitted in a Bayesian framework to abundance indices. Most stocks have seen their abundance sharply declining over time. All stocks combined, results of stock assessments suggest a 63% reduction compared to virgin state. Three fifth of demersal stocks are overexploited and excess in fishing effort was estimated until 75% for the worst case. We conclude by suggesting that the fishing of such species must be regulated and an ecosystem approach to fisheries management should be implemented in order to monitor the whole ecosystem.
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Kozobrod, Inna, M. Pyatinsky, and Elena Vlasenko. "AZOV SEA VIMBA INDICATOR ASSESSMENT OF THE STATE OF FISH POPULATION IN TERMS OF LACK OF BIOLOGICAL DATA BY LBI MODEL." Fisheries 2021, no. 3 (June 7, 2021): 68–75. http://dx.doi.org/10.37663/0131-6184-2021-3-68-75.
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Stock assessment of vimba population Vimba vimba (Linnaeus, 1758) in period 2015–2020 was performed by qualitative indicator method LBI (Length-Based Indicators) that allows to assess qualitative characteristics of the population and fisheries and MSY biological reference points. The indicator, qualitative approach to stock assessment was applied due to absence vimba population of stable stock-recruitment relationship (due to artificial reproduction exist), which makes impossible to apply surplus production approach to solve production equation dB/dt.
LBI model was performed based on available length-weight vimba frequencies dynamics information, which allows to evaluate qualitative population characteristics and fisheries impact. Model results shows no overexploitation signals: in period 2015–2020 fisheries are carried out in maximum sustainable yield level.
Indicator results according to reference points indicate no significant signals of reduction optimal length class (Lopt), small-size or large-size class. In 2016 and 2018 uncertain overexploitation of small-scale classes leads to no significant changes was underlined. In terms of biological and fisheries data lacking, LBI methods allow to perform stock assessment procedure more stable and robust then surplus or cohort approach, and output scientific advice to fisheries management.
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Gebremedhin, Shewit, Stijn Bruneel, Abebe Getahun, Wassie Anteneh, and Peter Goethals. "Scientific Methods to Understand Fish Population Dynamics and Support Sustainable Fisheries Management." Water 13, no. 4 (February 23, 2021): 574. http://dx.doi.org/10.3390/w13040574.
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Fisheries play a significant role in the livelihoods of the world population, while the dependence on fisheries is acute in developing countries. Fisheries are consequently a critical element for meeting the sustainable development (SDG) and FAO goals to reduce poverty, hunger and improve health and well-being. However, 90% of global marine fish stocks are fully or over-exploited. The amount of biologically unsustainable stocks increased from 10% in 1975 to 33% in 2015. Freshwater ecosystems are the most endangered ecosystems and freshwater fish stocks are worldwide in a state of crisis. The continuous fish stock decline indicates that the world is still far from achieving SDG 14 (Life Below Water), FAO’s Blue Growth Initiative goal and SDG 15 (Life on Land, including freshwater systems). Failure to effectively manage world fish stocks can have disastrous effects on biodiversity and the livelihoods and socio-economic conditions of millions of people. Therefore, management strategies that successfully conserve the stocks and provide optimal sustainable yields are urgently needed. However, successful management is only possible when the necessary data are obtained and decision-makers are well informed. The main problem for the management of fisheries, particularly in developing countries, is the lack of information on the past and current status of the fish stocks. Sound data collection and validation methods are, therefore, important. Stock assessment models, which support sustainable fisheries, require life history traits as input parameters. In order to provide accurate estimates of these life history traits, standardized methods for otolith preparation and validation of the rate of growth zone deposition are essential. This review aims to assist researchers and fisheries managers, working on marine and freshwater fish species, in understanding concepts and processes related to stock assessment and population dynamics. Although most examples and case studies originate from developing countries in the African continent, the review remains of great value to many other countries.
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Nurhakim, Subhat. "IMPLIKASI IUU FISHING DALAM PENGELOLAAN SUMBER DAYA IKAN DI INDONESIA." Jurnal Kebijakan Perikanan Indonesia 1, no. 1 (February 3, 2017): 61. http://dx.doi.org/10.15578/jkpi.1.1.2009.61-66.
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Pada tatanan dunia, regional, dan nasional, dewasa ini isu kegiatan yang berkaitan dengan IUU fishing adalah merupakan ancaman utama terhadap sediaan ikan. Telah banyak inisiatif international yang didukung oleh organisasi internasional seperti FAO telah menyiapkan International Plan of Action dari IUU Fishing. Walaupun jumlah negara yang mencoba mengembangkan National Plan of Action dari IUU Fishing terus bertambah, tetapi dalam beberapa hal, kegiatan IUU Fishing merupakan hal yang banyak terjadi dan merupakan ancaman nyata terhadap perikanan lokal. Adalah benar bahwa perhatian dunia terhadap IUU Fishing terus meningkat sebagai akibat yang nyata penurunan sediaan ikan dunia secara drastis. Perkiraan kasar secara keseluruhan menunjukkan bahwa paling tidak 30% dari hasil tangkapan perikanan dunia diperoleh dari kegiatan IUU Fishing. Ini memperlihatkan bahwa masalah IUU Fishing tersebut meningkat dengan kuat, terutama bila dilihat dari percepatan penurunan ketersediaan sumber daya perikanan. Tulisan ini menyajikan hal-hal yang berkaitan dengan pengkajian sediaan dan pengelolaan perikanan seperti juga halnya kegiatan IUU Fishing yang terjadi di Indonesia. Dampak IUU Fishing terhadap hasil pengkajiaan sediaan pada akhirnya digunakan sebagai informasi dasar untuk pengelolaan perikanan juga dibahas. Rekomandasi disampaikan dalam kaitannya untuk mengurangi kegiatan IUU Fishing dan meningkatkan pengkajian sediaan ikan dan pengelolaan perikanan.At global, regional, and national levels, issues associated with IUU fishing activities currently constitute a major world-wide threat to fisheries stocks. There have already been many international initiatives supported by international organizations such as the FAO which have been engaged in the International Plan of Action on IUU fishing. Although an increasing number of countries are trying to develop national plan of actions on IUU fishing, in many parts, IUU fishing practices are still common place and constitute a real threat to local fishers. Indeed, there is increasing global concern about IUU fishing practices due to the fact that global fish stocks are declining drastically. Approximate estimations suggest that overall at least 30% of world-wide fisheries catch is obtained from IUU fishing activities. This shows that the problem is increasingly severe, especially in view of the accelerating overall decline in available fisheries resources. This paper presents briefly regarding stock assessment and fisheries management as well as IUU fishing activities that undertake in Indonesian waters. The impact of IUU fishing to the result of stock assessment, that finally used as basic information for fisheries management is also discuss. Recommendation ismade in relation to eliminate IUU fishing activities and improvement of stock assessment and fisheries management.