Download or read book Developing a Data poor Stock Assessment Model for New Zealand Bycatch Species written by Callum Templeton and published by . This book was released on 2016 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study investigated methods pertaining to the assessment of data-poor fishery stocks within New Zealand. Recent modelling approaches (termed ‘N-mixture’) have appeared in the ecological literature that enable simultaneous estimation of abundance and detectability (gear efficiency in a fisheries context) from count data corresponding to a population of interest. This approach forms part of the quantitative risk assessment framework known as Sustainability Assessment for Fishing Effects, which has been applied to a range of species in Australian fisheries. There is potential for application of such methods in New Zealand, where an estimated 80% of fish stocks lack assessment under the Quota Management System. Various models were developed as part of this study in order to obtain quantitative estimates relating to catchability and abundance. These involved a mixture of statistical distributions (log-normal, Poisson, and binomial) and were implemented in the R and JAGS software. A range of simulations were devised to produce artificial data sets for model validation and analysis purposes. Models were analysed using a Bayesian hierarchical approach in order to estimate the parameters of interest. The models under investigation were also applied to red gurnard (Chelidonichthys kumu) data from the GUR 1 stock management area in northeastern New Zealand, to provide a case study for real-world applicability. Model validation revealed that recovering estimates of gear efficiency and abundance was possible using the approach considered here. Analysis simulations provided information regarding the potential sources of bias, variability and incompatibility arising from assumptions in model specification and data generation. These findings were also considered in the context of application to red gurnard. The most important issues highlighted by this study include the role of over-dispersion on modelling and data requirements, handling zeroinflated data sets, and bias introduced from catch reporting procedures in commercial fisheries within New Zealand. The results of this study provide an important first step in assessing data-poor stocks, providing a cost-effective means of obtaining key fishing parameters without significant data requirements. Further research into this area will enable these findings to be applied alongside other methods in order to gauge the sustainability of fishing impacts on bycatch species.
Download or read book Evaluating the Data poor Fishery Stock Assessment Method DB SRA written by Brandon R. Owashi and published by . This book was released on 2014 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Depletion-Based Stock Reduction Analysis (DB-SRA; Dick and MacCall, 2011) is a catch-only fisheries stock assessment model that has been developed to estimate an overfishing limit (OFL) in data-poor situations. DB-SRA projects the biomass trajectories of a stock by means of a catch time series and five parameters: the instantaneous, per annum, rate of natural mortality (M), age at 50% maturity, F[subscript MSY]/M, B[subscriptMSY]/B0, and the predicted depletion of the stock from its unfished condition. F[subscriptMSY]/M is the rate of fishing mortality associated with the maximum sustainable yield (MSY) divided by the natural mortality rate, and B[subscriptMSY]/B0 is the biomass level associated with the MSY divided by the unfished level of biomass. DB-SRA performs a Monte Carlo simulation where a large number of random parameter draws are made based on the input parameter's prior distribution. Based on the catch time series, a biomass trajectory is produced to estimate a feasible set of input parameters and an OFL. The run and corresponding set of input parameters are not retained if the biomass trajectory goes below zero. In instances where the input parameter prior distributions are unknown, Dick and MacCall (2011) proposed a set of default values for two life history types (rockfish and flatfish). Although DB-SRA has been evaluated to some extent and is currently being used for management of data-poor species on the U.S. west coast, further evaluation is warranted. Like other fisheries assessment models, DB-SRA makes several assumptions that may have large influence on outputs and have largely gone untested. First, in essence DB-SRA assumes that only mature fish are caught in the fishery; this is rarely true on the U.S. West Coast and elsewhere, particularly for species with substantial recreational catch. Second, most stock assessment methods, including DB-SRA, are applied to large regions (e.g., U.S. west coast), assuming the population dynamics and fishing behavior remain consistent across the entire area. Market demands and habitat, among other factors, can lead to heterogeneity in population dynamics and fishing behavior. For instance, immature fish are often caught in recreational fisheries, but commercial fisheries tend to target larger fish, causing fishing impact to change across regions. I developed a two-region operating model that simulated data to generate input parameter expected values and a catch time series for each region, then conducted a factorial experiment to investigate the effect of four factors on DB-SRA (version 4) results: (1) different positions of the selectivity curve (the relative vulnerability to fishing of each age class) relative to the maturity curve; (2) spatial scale (separate by region versus combined); (3) exploitation history; and (4) life history type (rockfish and flatfish). The position of the selectivity curve influences the accuracy of the OFL estimates from DB-SRA, whereas the exploitation history has little effect. The OFL estimates are overestimated when the selectivity curve is to the right of the maturity curve and underestimated when the selectivity curve is to the left of the maturity curve. DB-SRA produces higher OFL estimates when two regions are used instead of one large region. Dividing the catch data into multiple regions resulted in higher OFL estimates than one combined region when the same input parameters and catch time series were used. An updated production function, for mimicking population dynamics, was implemented in DB-SRA (version 4), creating separate time lags for mortality and production (recruitment and growth). Instead of setting the time lags for mortality and production equal to the age at 50% maturity (version 3), the time lag for mortality has been changed to one year (version 4). Although the version 4 DB-SRA model has been used for fishery management, it has not been formally evaluated against version 3 to understand the impacts of this change on model results. To investigate the two versions, I looked at different positions of the selectivity curve relative to the maturity curve, different exploitation histories, and varying spatial scale for two life history types. The OFL estimates from version 3 of DB-SRA were larger than the OFL estimates from version 4, which is also evident in the biomass trajectories. The biomass trajectories from version 3 are always greater than the respective biomass trajectories from version 4. Although the OFL estimates from version 4 are not always less biased than those from version 3, the estimates from version 4 are always more precautionary and significantly reduce the chances for overestimating the OFL. The identification of factors that influence DB-SRA OFL estimates could demonstrate how DB-SRA can be adjusted to produce less biased OFL estimates in more situations. The change made in the production function between versions 3 and 4 of DB-SRA makes OFL estimates more precautionary; but does not always reduce the bias in the median OFL estimate. The results from this study could provide information to fisheries managers so that DB-SRA could be potentially improved and is applied in appropriate situations.
Download or read book Stock Assessment for Fishery Management written by Daniel D. Hoggarth and published by Food & Agriculture Org.. This book was released on 2006 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: This publication contains guidelines for fish stock assessment and fishery management using the software tools and other outputs developed by the UK Department for International Development's Fisheries Management Science Programme (FMSP) from 1992 to 2004. It includes a CD-ROM with the installation files for each of the four FMSP software tools: LFDA (Length Frequency Data Analysis), CEDA (Catch Effort Data Analysis), YIELD and ParFish (Participatory Fisheries Stock Assessment).
Download or read book Improving Fish Stock Assessments written by Committee on Fish Stock Assessment Methods and published by National Academies Press. This book was released on 1998-03-13 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean harvests have plateaued worldwide and many important commercial stocks have been depleted. This has caused great concern among scientists, fishery managers, the fishing community, and the public. This book evaluates the major models used for estimating the size and structure of marine fish populations (stock assessments) and changes in populations over time. It demonstrates how problems that may occur in fisheries data--for example underreporting or changes in the likelihood that fish can be caught with a given type of gear--can seriously degrade the quality of stock assessments. The volume makes recommendations for means to improve stock assessments and their use in fishery management.
Download or read book Data limited Research in Stock Assessment to Increase the Understanding of Fisheries Resources and Inform and Improve Management Efforts written by Giuseppe Scarcella and published by Frontiers Media SA. This book was released on 2023-04-10 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Guide to Fisheries Stock Assessment written by Andrew B. Cooper and published by . This book was released on 2006 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stock Assessment written by Vincent F. Gallucci and published by CRC Press. This book was released on 1995-10-25 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stock Assessment: Quantitative Methods and Applications for Small Scale Fisheries is a book about stock assessment as it is practiced. It focuses on applications for small scale or artisanal fisheries in developing countries, however it is not limited in applicability to tropical waters and should also be considered a resource for students of temperate fishery management problems. It incorporates a careful sample design, various mathematical models as a basis for predicting consequences for stock exploitation, and discusses the impact of exploitation on non-targeted species. This was a unique concept involving a collaborative effort between U.S. and host country scientists to address issues of regional and global concern through innovative research. Unlike other books on stock assessment that show mathematical models, this is the only book of its kind that discusses how an assessment is carried out. It looks at the field as a whole and includes sampling, age determination and acoustics. The book represents the culmination of a nine-year program financed by the United States Agency for International Development to provide new or improved methods of stock assessment for artisanal fisheries.
Download or read book Developing a Stock Assessment for New Zealand Bluenose written by Matthew R. Dunn and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stock Assessment written by Vincent F. Gallucci and published by CRC Press. This book was released on 2023-05-31 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stock Assessment: Quantitative Methods and Applications for Small Scale Fisheries is a book about stock assessment as it is practiced. It focuses on applications for small scale or artisanal fisheries in developing countries, however it is not limited in applicability to tropical waters and should also be considered a resource for students of temperate fishery management problems. It incorporates a careful sample design, various mathematical models as a basis for predicting consequences for stock exploitation, and discusses the impact of exploitation on non-targeted species. This was a unique concept involving a collaborative effort between U.S. and host country scientists to address issues of regional and global concern through innovative research. Unlike other books on stock assessment that show mathematical models, this is the only book of its kind that discusses how an assessment is carried out. It looks at the field as a whole and includes sampling, age determination and acoustics. The book represents the culmination of a nine-year program financed by the United States Agency for International Development to provide new or improved methods of stock assessment for artisanal fisheries.
Download or read book Review of Northeast Fishery Stock Assessments written by National Research Council and published by National Academies Press. This book was released on 1998-04-17 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: The collapse of cod, flounder, and haddock fish stocks in the Northeast United States has caused widespread concern among managers and fishers in the United States and Canada. The diminishing stocks have forced managers to take strict regulatory measures. Numerous questions have been raised about the adequacy of stock assessment science used to evaluate the status of these stocks and the appropriateness of the management measures taken. Based on these concerns, Congress mandated that a scientific review of the methodology and data used to evaluate these stocks be conducted. In this volume, the committee concludes that although there are improvements to be made in data collection, modeling uncertainty, and communicating between fishers, managers, and scientists, the scientific methods used in the Northeast stock assessments are sound. Recommendations are made on how the stock assessment process can be improved.
Download or read book Using Information for Data rich Species to Inform Assessments of Data poor Species Through Bayesian Stock Assessment Methods written by André E. Punt and published by . This book was released on 2005 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development and Application of a Spatial Stock Assessment Model for P ua Haliotis Iris written by Philipp Neubauer and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Accounting for Variability and Biases in Data limited Fisheries Stock Assessment written by Merrill B. Rudd and published by . This book was released on 2017 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many regions of the world have very few stocks assessed, often due to limited data quality or quantity or lack of trained scientists to apply and interpret stock assessments. These same areas with fewer assessments perform worse across fishery management attributes, including research capacity, management, enforcement, and socioeconomics. Some studies have used the limited data available to approximate the status of these “unassessed” stocks and find them to be declining compared to assessed stocks. Global assessments of “unassessed” stocks are informed by many attributes of the stock, one of which is the trend in reported catch to the U.N. Food and Agriculture Organization. These assessments assume that the catch data are accurate, at least in trend if not in magnitude. However, quantifying catch is a major challenge due to commonly misreported sectors such as discards, small-scale, recreational, and illegal, unreported, unregulated fisheries. One approach is to improve catch data by improving monitoring programs or conducting catch reconstructions. Another approach is to collect alternative data types to conduct stock assessments. Stocks that are not assessed because they have the lowest information or research capacity appear more likely to be unsustainable, and further research and management action is required to improve the status of the data- and research-capacity-limited fisheries. This dissertation addresses issues of data quality in the monitoring process and data limitation in the assessment process. Chapter 1 addresses an issue of data quality in asking, “does unreported catch lead to overfishing?” We used simulation analysis to demonstrate that if catch is misreported at a constant rate, surplus production models can still estimate unbiased stock status and would avoid overfishing with effective management. If catch misreporting is increasing over time, stock assessments would recommend harvest limits that would lead to under-exploitation, while decreasing reporting rates lead to over-exploitation. This question is relevant to fisheries around the world dealing with uncertainties in catch reporting in their stock assessment, as well as current debates over the use of catch reconstructions. In Chapter 2 stock assessments are examined for fisheries that only have length composition data and biological information, since it is often easier to collect length measurements than to quantify total catch. Length measurements from samples of the catch, referred to as length composition data, can be contrasted with expected length composition in an unfished state to reveal information about fishing mortality, recruitment, and selectivity. Most data-poor length-based stock assessment methods assume the population is in equilibrium, i.e. that fishing mortality and recruitment have not changed within one generation of the species. In this chapter we present a Length-based Integrated Mixed Effects (LIME) model that relaxes this equilibrium assumption and directly estimates variable fishing mortality and recruitment using the same data inputs as other length-based methods. Using simulation testing we demonstrated LIME performs best for life history types with a maximum age of less than 20 years, and is unbiased across a range of recruitment and fishing mortality patterns, provided individual growth parameters are known. LIME also has the capability of including multiple years of length data, abundance indices, and catch time series when available. LIME is a flexible new tool for stock assessments of fish usually caught as bycatch and other small-scale fisheries. Chapter 3 applies LIME and the equilibrium-based Length-Based Spawning Potential Ratio (LB-SPR) methods to assess a medium-lived Costa Rican spotted rose snapper, Lutjanus guttatus, and short-lived Kenyan rabbitfish, Siganus sutor. LIME estimated the Costa Rican snapper fishery to be overfished in the most recent year of data after a period of full exploitation, whereas LB-SPR estimated more variability in stock status throughout the time series but the fishery was above the target reference point in the most recent year of data. LIME estimated the rabbitfish fishery to have undergone a period of overexploitation in the late 1990s and early 2000s, but fishing mortality has continually decreased over time resulted in a recovered stock in the most recent year of data. Alternatively, LB-SPR estimated the stock slightly less than the SPR target. Chapter 3 presented the first empirical LIME assessment and comparison with a commonly-used alternative method, and presented guidelines for future LIME applications.
Download or read book Research in Fisheries written by University of Washington. College of Fisheries and published by . This book was released on 1991 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Adressing the Reliability of Data poor Stock Assessment Methods to Provide Advice on the Status of Small scale Fisheries written by John Gabriel Ramírez Téllez and published by . This book was released on 2020 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Small-scale fishers are often identified as key players in the recovery of overexploited fish and invertebrate stocks supplying food for rural people and contributing to achieving healthy marine ecosystems. Stocks harvested by small-scale fisheries tend to be largely unassessed, but methods based on the data-limited toolbox exist that help provide information on exploitation status for fished stocks that do not have historical time series of catches, as usually occur in small-scale fisheries. Many of the data-limited methods follow length-based assessment approaches, which assume steady state, use at least length structure derived from fishery and knowledge on the life history parameters of the fished species. Accordingly, this thesis aimed at addressing the reliability of data-poor stock assessment methods in providing advice on the status of small-scale fisheries lacking knowledge of catch history. The data-rich bottom trawl fishery for European hake (Merluccius merluccius) in GSA 06 (Northwest Mediterranean Sea) was assumed as data-limited. This case study allowed me to test the performance of the pseudo-cohort Virtual Population Analysis (VPA) when input data are considered well known and unbiased. The same fishery but held in GSA 01 (Southwest Mediterranean Sea) was used as data-limited case study to introduce the uncertainty derived from parameterizing the length-based spawning potential ratio (LB-SPR) model with two contrasting growth hypotheses. Acknowledging challenges faced by stock assessment of small-scale fisheries around the world, I considered high input-data bias and large outputs uncertainty. The effect of biases in fishery data and uncertainty in life-history parameters on the outputs of the pseudo-cohort VPA model was explored by assessing the small-scale Wayuu fisheries for lane snapper (Lutjanus synagris) and white grunt (Haemulon plumierii) in the northern Colombian Caribbean Sea. An extreme, but common, case of uncertainty in small-scale fisheries was explored through assessing the beach fishery of the Peruvian grunt (Anisotremus scapularis) in the central coast of Peru on the Pacific Ocean, holding poor information on life-history parameters and catches. My findings indicate that the pseudo-cohort VPA may offer useful information regarding the exploitation trend but the absolute values of the indicators do not accurately express the fishing mortality and stock size among years for the European hake. The SPR estimates for this species is not specially linked to the growth hypothesis, and estimates of the ratio of fishing mortality to natural mortality (F/M) and the SPR value depend on the sample size and representation of the stock structure. The contribution of the information derived from the participatory monitoring of small-scale fisheries in Colombia, instead of using only official fishery data, largely demonstrated an improving picture of the exploitation of the lane snapper and white grunt. The uncertainty related to estimates of the von Bertalanffy growth parameters and natural mortality of the Peruvian grunt could be addressed but an accurate definition of SPR was not straightforwardly achieved. This thesis highlights that the data-limited methods assuming a steady state might contribute to defining the status of the small-scale fisheries. However, the stock status is importantly affected by bias in the input data, the available knowledge on the assessed fisheries and how fishery fit the model assumptions." -- TDX.
Download or read book Review of New Zealand s Scallop Fishery Stock Assessment Data and Methods written by Stephen A. Smith and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Assessment Approaches to Support Bycatch Management for Marine Mammals written by Tessa Francis and published by Frontiers Media SA. This book was released on 2022-06-21 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt:
