1,721,095 research outputs found
Handbook of Marine Fisheries Conservation and Management
No full textThis handbook is the most comprehensive and interdisciplinary work on marine conservation and fisheries management ever compiled. It is the first to bridge fisheries and marine conservation issues. Its innovative ideas, detailed case studies, and governance framework provide a global special perspective over time and treat problems in the high seas, community fisheries, industrial fishing, and the many interactions between use and non-use of the oceans. Its policy tools and ideas for overcoming the perennial problems of over fishing, habitat and biodiversity loss address the facts that many marine ecosystems are in decline and plagued by overexploitation due to unsustainable fishing practices. An outstanding feature of the book is the detailed case-studies on conservation practice and fisheries management from around the world. These case studies are combined with 'foundation' chapters that provide an overview of the state of the marine world and innovative and far reaching perspectives about how we can move forward to face present and future challenges. The contributors include the world's leading fisheries scientists, economists, and managers. Ecosystem and incentive-based approaches are described and complemented by tools for cooperative, participatory solutions. Unique themes treated: fisher behavior and incentives for management beyond rights-based approaches; a synthesis of proposed 'solutions'; a framework for understanding and overcoming the critical determinants of the decline in fisheries, degradation of marine ecosystems, and poor socio-economic performance of many fishing communities; models for innovative policy instruments; a plan of action and adoption pathways to promote sustainable fishing practices globally. Collectively, the handbook's many valuable contributions offer a way forward to both understanding and resolving the multifaceted problems facing the world's ocean
The good, the bad and the ugly: learning from experience to achieve sustainable fisheries
Full text linkA broad range of fisheries-management approaches has been used around the world with varying degrees of success. The Fifth International Mote Symposium focused on contrasting strategies and contexts associated with successful experiences with others associated with management failures. A number of general principles for successful fisheries management emerged. These principles emphasize the need to address the causes of management failures directly by creating institutional structures that provide incentives to stop the race for fish and to increase responsibility and accountability of all stakeholders—fishers, scientists, and managers.Fil: Parma, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Hilborn, Ray. University of Washington; Estados UnidosFil: Orensanz, Jose Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin
Fishing for nutrition - improving the connection between fisheries, the food system and public health
No full textThesis (Ph.D.)--University of Washington, 2019Fish and shellfish are rich in micronutrients. As aquaculture production grows and the pathways to sustainably manage our capture fisheries become clear seafood is positioned to play a major role in the fight against malnutrition, which is back on the rise. This PhD research endeavored to improve our understanding of how seafood production can contribute to the food system. Chapter 2 assessed the policy landscape related to the integration national-level fishery and health policies to determine where these policies are most aligned and under what conditions. The analysis evaluated 165 health and 158 fishery national-level policies around the world. Overall, however, results indicated low levels of integration in fishery and health policies, indicating that there is considerable potential for improvement. These results establish a foundational understanding of the status of national policies connecting fisheries to the healthy food system. Chapter 3 and Chapter 4 were part of the same project that evaluated at the regional scale of the US West Coast the current and potential contribution of rebuilding capture fisheries after a history of overfishing to the healthy food,. Chapter 3 used interview methods to learn from positive deviant case studies already achieving success. Chapter 4 utilized a mixed methodology that brought together quantitative and qualitative approaches. Quantitative data was synthesized to identify where affordable, underutilized fish species overlap with high food need communities who have the fishing capacity to access them. Interviews were used to determine challenges and enabling conditions of actors throughout the supply chain. Chapter 5 evaluating of the environmental impacts of nutrient-rich food production that compares diverse capture and aquaculture seafood production to other animal sourced and vegetable food groups by linking and evaluating environmental impact information from life-cycle assessments and nutrition information. Results indicate that some fish and shellfish have environmental impacts at least as low as vegetables when considering their potential to contribute nutrients towards a healthy, sustainable diet. There are 6 supplemental spreadsheets including the raw data used to compute the impact ratios in Chapter 5 submitted alongside this ETD. There is one spreadsheet for each of the 6 impacts: Greenhouse gas emissions (GHG_table.csv), Acidification (Acid_table.csv), Eutrophication (Eutro_table.csv), Fuel use (Fuel_table.csv), Water use (Water_table.csv) and Land use (land_table_csv). Each of these spreadsheets includes the environmental impacts associated with each product and food group along with the daily requirements and nutrient richness index calculated from the daily requirements
Salmonid Selection, Evolution, and Historical Abundance Patterns
Full text linkThesis (Ph.D.)--University of Washington, 2015Pacific salmon represent an important group of species both from both cultural and economic perspectives. Given the importance of salmonids in marine and freshwater ecosystems, as a component of human food security, it is important to understand what natural and anthropogenic factors influence the evolutionary and demographic dynamics of population across their range, and develop quantitative tools to aid in the implementation of sustainable management practices. This dissertation is focused upon: (i) evaluating whether selective predation by brown bears (Ursus arctos) depends upon the density of their sockeye salmon (Oncorhynchus nerka) prey, (ii) quantifying strength and direction of natural and anthropogenic selection forces and life history tradeoffs that shaping optimal phenotypic distributions for populations of sockeye in Bristol Bay, Alaska, (iii) development of methods for reconstructing salmon run size by partitioning mixed-stock catches while accounting for differences in availability to harvest within common fishing areas and interception in spatially proximate terminal fishing districts using both age and genetic composition of catch data, (iv) simulation testing of a stage-structured statistical life cycle model for evaluating the natural and anthropogenic drivers of Chinook salmon (O. tshawytscha), and (v) an application for the statistical life cycle model to seven populations of fall and spring-run Chinook in the Sacramento River watershed of California
The utility of catch-per-unit-effort when assessing and managing long-lived fish stocks
Full text linkThesis (Ph.D.)--University of Washington, 2013The research in this Ph.D. dissertation focuses on the relationship between fishery-dependent catch-per-unit-effort (CPUE) and abundance and how its use when assessing and managing fisheries may be affected by some of its shortcomings. CPUE data are often used to provide information on the historical and current stock size, but changes in CPUE may not be proportional to abundance. Hyperstability is when CPUE declines slower than abundance and can result in optimistic estimates of abundance and risk of overfishing. Hyperdepletion is when CPUE declines faster than abundance and using these data in an assessment can produce pessimistic estimates of abundance. Assuming a proportional relationship between CPUE and abundance when CPUE actually has a nonlinear relationship with abundance can misinform management and result in overfishing or lost yield. Instead, the nonlinear relationship can be modeled and estimated. Three stand-alone chapters are presented in this dissertation with methods and results from analyses estimating the amount of nonlinearity in the relationship between CPUE and abundance and its implications on fisheries management. The first chapter investigated the nonlinearity between empirical CPUE data and abundance from orange roughy fisheries in Australia and New Zealand. Data from four orange roughy stocks were integrated using a Bayesian hierarchical state-space model to estimate the hyperparameters of a distribution for a nonlinearity parameter in the relationship between CPUE and abundance. Hyperdepletion was more probable than hyperstability and a prior distribution for an unknown stock showed a 83\% probability of hyperdepletion. This study is unique because it used data from the beginning of a fishery and created a prior distribution that may be used in future assessments. The second chapter used simulation to look at the ability to estimate nonlinearity in CPUE data using different models, assumptions, and types of data. A deterministic delay-difference model, a deterministic age-structured model, and a state-space delay-difference model were used to estimate the nonlinearity parameter of simulated CPUE data with a hyperstable, proportional, or hyperdepleted relationship to abundance. Estimates of the nonlinearity parameter were mostly unbiased, but highly variable. Using an informative prior distribution resulted in lower variance, but higher bias when the prior was not congruent with the true level of nonlinearity. Overall, the state-space model showed the best performance, and an informative prior distribution was useful as long as it is appropriate, justifiable, and wide enough to support all possible values of the nonlinearity parameter. The final chapter performed a management strategy evaluation to determine the consequences of managing a fish stock with and without estimating a nonlinearity parameter between CPUE and abundance. An age-structured operating model was used to simulate a true population from which CPUE and survey data were generated, where CPUE data were either hyperstable, proportional, or hyperdepleted. Estimation models with the nonlinearity parameter estimated or fixed at proportionality were used to estimate population trajectories from the simulated data. Two-area age-structured operating models with movement dependent on fishing effort and density-dependence were also investigated. The benefits to estimates of stock status and yield objectives when estimating a nonlinearity parameter were dependent on the true underlying relationship between CPUE and abundance. Hyperstable scenarios were especially risky, and should always be accounted for, or at least acknowledged, in a management strategy. Hyperdepletion scenarios, on the other hand, may seem to be less of a concern due to reduced conservation risk, but the negative consequences of reduced yield, at least in the short term, and a pessimistic view of the stock, and thus the management system, make it worthwhile to at least acknowledge the potential for hyperdepletion and that not accounting for it is a chosen management strategy. In the long-term, yield was similar whether or not nonlinearity was estimated, but if when estimating nonlinearity, risk to the stock was reduced when CPUE were hyperstable and although risk increased when CPUE showed hyperdepletion, stock status was typically always higher than the hyperstable scenarios. Nonlinearity in CPUE is common in many fisheries and it was seen that CPUE declined faster than abundance during the initial development of orange roughy fisheries. The presence of hyperdepletion can result in pessimistic views of stock status which may result in lost yield, the closure of fisheries, and conflict amongst user groups. Estimating a nonlinearity parameter in assessments and acknowledging that nonlinearity exists can improve management by bringing catches and stock depletion closer to target levels
Stock Status and Management in Tuna Fisheries: from data-rich to data-poor
Full text linkThesis (Ph.D.)--University of Washington, 2018Tunas and billfishes are large migratory species managed by Regional Fisheries Management Organizations (tRFMOs). The current status of these species is well known, and most of the large commercial tuna stocks are managed at sustainable levels. We found that most of the overfished tuna and billfish populations are showing signs of rebuilding as a consequence of the implementation of strong management measures such as fishing quotas. However, management performance among tRFMOs is highly variable among oceans and it is mainly correlated with the overall economic dependence of individual members of the tRFMOs on tuna fisheries. When countries with low governance capacity account for the greatest proportion of total tuna catches, management controls are, on average, harder to implement. On the other hand, some non-commercial valuable tuna stocks, such as mackerels and bonitos, managed under the umbrella of tRFMOs remain unassessed, mainly because of insufficient quantitative data, particularly total catch. Preliminary assessments for these stocks based only on length composition data from the catch, showed that some of these stocks are experiencing overfishing. These results should encourage the management body in the Atlantic Ocean to take management actions to protect these stocks from overfishing as well as improve data collection programs. When comparing the performance of some length-based and catch-based data limited assessment methods, we found that in many cases, length-based assessments performed as well as other catch-based models. Nevertheless, the performance of different data-limited methods depended not only on the type of data available, but on prior knowledge about the exploitation history of the stock and the biology of each species. We hope that this dissertation helps to improve the current management system for data-rich tuna stocks by highlighting successful management strategies, as well as to improve the estimation of stock status for data-poor tuna fisheries
Informative Data and Uncertainty in Fisheries Stock Assessment
Full text linkThesis (Ph.D.)--University of Washington, 2016-02Uncertainty is an integral part of fisheries stock assessment. Successful resource management requires scientific analysis to evaluate the uncertainty about the status of each stock and related quantities of interest. A failure to incorporate uncertainty into management advice increases the risk of suboptimal yields and can lead to a fishery collapse. In practice, it is not always clear which features of stock assessment data make them informative or uninformative, and it is also unclear how well different statistical methods are likely to perform when evaluating uncertainty. This study uses simulation analysis to measure the performance of alternative methods, based on a large number of simulated datasets where the underlying true values are known. The methods are then applied to data from an actual fishery, and the overall inference takes into account the performance of the methods in the simulations. The results show that the historical levels of stock size and harvest rate greatly affect how informative the data are about the current stock status. The key parameters natural mortality M and stock-recruitment steepness h pose challenges when it comes to statistical estimation, and long-term management advice is likely to depend strongly on the estimated or assumed values of M and h. The most informative fishing history is one where the data include years of high and low stock size, which is informative about h, as well as high and low harvest rates, which is informative about M. The results also indicate that confidence intervals describing the uncertainty about the stock status and other quantities of interest are likely to be too narrow in general. Benchmark analysis indicates that the delta method, Markov chain Monte Carlo (MCMC), and profile likelihood approaches are likely to perform better than the bootstrap for quantifying uncertainty. A bias correction algorithm for the bootstrap improved its performance, but not enough to match the performance of the other methods. Additional approaches to evaluate the estimation uncertainty include retrospective analysis and bivariate confidence regions for the current stock status. The use of harvest control rules to incorporate uncertainty into management advice is also discussed. The main value of this study is to present a comprehensive overview and evaluation of methods to analyze uncertainty. The study concludes with a checklist of recommendations for confronting uncertainty in stock assessment
Utility and implications of no-take marine reserves in fishery management strategies
No full textThesis (Ph.D.)--University of Washington, 2012This work explores (1) the potential for using marine reserves to manage data-poor fish populations, (2) the potential for marine reserves to influence the performance of commonly used stock assessment approaches relative to alternative approaches that explicitly account for a marine reserve, and (3) hypotheses about the role of older females to population persistence and arguments that marine reserves are needed to maintain this role. In Chapter 1, the potential use of the ratio of the density of fish outside a marine reserve to that inside the reserve in a fishery management control rule (DRCR) is evaluated by Management Strategy Evaluation. The cumulative catch under the optimal DRCR was 90% of the cumulative catch from an optimal constant effort rule (CER). A small range of parameter values for the DRCR produced 75% or more of the cumulative catch produced from optimal CERs for a variety of assumptions about biology and initial stock status. The optimal DRCR was most sensitive to movement patterns of larvae and adults and survey variability. In Chapter 2, a simulation model was used to analyze the ability of several stock assessment approaches to estimate current biomass after the implementation of a marine reserve. Results show that assessing populations as a single stock without accounting for a no-take marine reserve and performing separate assessments for fished and protected areas can lead to severely biased estimates of biomass. An assessment approach which explicitly accounted for fish movement was robust to uncertainty in movement patterns. In Chapter 3, two popular hypotheses are modeled; one assumes that older mothers produce larger offspring capable of surviving longer starvation periods than offspring from younger mothers. The other modeled hypothesis is that mothers of different ages spawned in different times or locations. Recruitment variability was 55-65% lower than for control models in the absence of fishing and increased with increases in fishing mortality rates for both models. A marine reserve policy did not benefit measures of sustainability for either model
Exploitation Rate Reference Points for West Coast Rockfish: Are They Robust and Are There Better Alternatives?
Full text linkWe explore several aspects of the robustness of exploitation rate reference points as a management tool. The spawner- recruit curve is an important consideration when developing exploitation rate reference points. The spawner-recruit curves for West Coast rockfish Sebastes spp. suggest low productivity compared with other tocks, but our ability to produce reliable estimates of productivity is hindered by the scarcity of reliable, fishery-independent surveys, the short time span of the data, high aging error, and the low exploitation levels. Implementation of reference exploitation rates usually assumes that we can estimate the absolute stock size and the ratio of current to virgin stock size. We show that management by reference exploitation rates is not robust to overestimation of stock size; in such cases, overexploited stocks will continue to be overexploited. We also show that if F55% exploitation rates (i.e., rates that reduce the spawning potential per recruit to 55% of its value in the unfished state) are used and productivity for an individual stock is comparable to that for other stocks around the world, we would unnecessarily impose catch reductions. We evaluate a management policy that seeks to maintain healthy stocks at or near current levels regardless of the absolute abundance, and we show that such a policy produces desirable results both when the stock size is overestimated and when stock productivity is underestimated. For stocks that are judged to be in need of rebuilding, current management policies seek to reduce catch to very low levels regardless of the reference point.Fil: Hilborn, Ray. University of Washington; Estados UnidosFil: Parma, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Maunder, Mark. Inter-American Tropical Tuna Commission; Estados Unido
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