Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 58 for “"stock assessment"”.
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Bayesian statistics for fishery stock assessment and management
… about the use of Bayesian statistics in fishery stock assessment and management. Multidimensional posterior distributions replace classical parameter estimation in surplus-production and delay-difference models. The maximization of expected utilities replaces the estimation of optimal policies. …
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Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii
… jig CPUE data are presented. The dynamics of the stock biomass on the spawning grounds were modelled in order to assess the effects of current levels of effort and the existing closed season on the resource. The dynamics of the stock and the fishery were captured by a simple biomass-based model. …
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Fish stock assessment by a statistical analysis of echo sounder signals
… in this regard, as it provides a rapid means of assessment. Two acoustic assessment techniques currently used are the echo counting and echo integration· methods. The echo counting method requires that only single fish echoes are present in the backscatter from the shoal, while the echo …
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Influence of the Estimator Selection in Scalloped Hammerhead Shark Stock Assessment
… scalloped hammerhead shark or other fish stocks with poor data available. This study found the population was overfished and suffering overfishing. Therefore, based on our research and that there was very low evidence of recovery according with the last data available, we suggest …
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The Effects of Ageing Error on Stock Assessment for Weakfish Cynoscion regalis
Inherent uncertainties in the stock assessment for weakfish have precluded accurate and consistent advice concerning the management of commercial and recreational fisheries. Error within ageing techniques, used to assess relative age frequencies within commercial and recreational harvest, has been …
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The impact of bias in length frequency data on an age structured fisheries stock assessment model
… models are widely used in fisheries stock assessment. These models have been become increasingly complex over recent decades, allowing them to incorporate a larger variety of fisheries data. These typically include information regarding annual fishery yields, indices of abundance and …
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Exploring spatial heterogeneity of CPUE year trend and nonstationarity in fisheries stock assessment, an example based on Atlantic Weakfish (Cynoscion regalis)
… dynamics modeling is needed to evaluate the stock status and fisheries management plans to provide robust model and management strategies. Atlantic Weakfish (Cynoscion regalis), one important commercial and recreational fish species along the west coast of Atlantic Ocean that was found to be …
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Identification and incorporation of quantitative indicators of ecosystem function into single-species fishery stock assessment models and the associated biological reference points
… summer and fall Southeast Area Monitoring and Assessment Program (SEAMAP) bottomfish trawl surveys were used to identify spatial and temporal indicators in the northwestern Gulf. Cluster analysis and nonmetric multidimensional scaling analysis identified four distinct demersal fish communities …
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Fishery, population dynamics and stock assessment of geelbek (Atractoscion aequidens), a commercially important migrant fish species off the coast of South Africa
… are comprised of immature fish, making the stock vulnerable to growth overfishing. Adults (>5 years) migrate seasonally to spawn off KwaZulu-Natal and congregate in offshore shoals at night. These spawning aggregations allow fishermen to catch large numbers of fish, making geelbek also …
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Assessment of the South Atlantic Red Porgy (<i>Pagrus pagrus</i>) Population Under a Moratorium
… off the coast of the southeastern United States. Stock assessments performed on this species since 1985 have shown a population in decline. As a result, a number of management actions were put in place, including a harvest moratorium in 1999. Stock assessments for many marine species, including …
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ESTIMATION OF MORTALITY RATES FOR THE GULF MENHADEN STOCK AND REFERENCE POINT IMPLEMENTATION FOR THE FISHERY
<p>The Gulf menhaden stock is the target of a large commercial fishery in the Gulf of Mexico. To address the needs of both the stock and fishery, I performed two studies. I first addressed the natural mortality rates currently used in the Gulf menhaden stock assessment. To update these rates, I …
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Study on fisheries resources with particular reference to red coral, spiny lobster and other target demersal species in Sardinian Seas
… by addressing critical knowledge gaps in the assessment of key commercial species: red mullet (Mullus barbatus), red coral (Corallium rubrum) and spiny lobster (Palinurus elephas). These resources represent both ecological keystones and economic pillars for regional small-scale fisheries, yet …
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Bayesian hierarchical approaches to analyze spatiotemporal dynamics of fish populations
… of fish populations is important for both stock assessment and fishery management. I explored the impacts of environmental and anthropogenic factors on spatiotemporal patterns of fish populations, and contributed to stock assessment and management by incorporating the inherent spatial …
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Investigating the performance of process-observation-error-estimator and robust estimators in surplus production model: a simulation study
… black sea bass (Centropristis striata) southern stock. Our results indicated that POE_N is the estimator with best performance among all six estimators with regard to both accuracy and precision for most of the cases. POE_N is also the robust estimator to outliers, atypical values, and …
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Multi-Species Models of Time-Varying Catchability in the U.S. Gulf of Mexico
… catchability coefficient is used in most marine stock assessment models, and is usually assumed to be stationary and density-independent. However, recent research has shown that these assumptions are violated in most fisheries. Violation of these assumptions will cause underestimation of stock …
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Informing U.S. Caribbean fisheries management through simulation modeling: a case of length-based mortality estimation models
Length-based stock assessment models estimating mortality rates are attractive choices for assessing fisheries with data deficiencies. The U.S. Caribbean is exploring using these models and trying to optimize their commercial sampling program for such a model. A simulation model was constructed to …
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Spatial and temporal heterogeneity in life history and productivity trends of Atlantic Weakfish (Cynoscion regalis) and implications to fisheries management
The biological characteristics of fisheries stocks that are assessed for management considerations are rarely homogeneous over time or space. However, stock assessment scientists largely ignore this heterogeneity in their models. This thesis addresses the effects of spatial and temporal …
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Fishing patterns around the Cape Peninsula National Park : implications for a fisheries monitoring program
… Areas and to provide data that are relevant to stock assessment models. Personnel and cost implications of the monitoring program will be estimated.
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The assessment of and management procedure development for the Namibian Monkfish resource
… of this thesis is to undertake a Bayesian assessment of the resource, and to use this as the basis to develop an Operational Management Procedure (OMP) for the resource. First, the biology, history of the fishery, and the history of monkfish stock assessment and management are reviewed …
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