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No Thumbnail AvailableBook (series)Technical studyIntroduction to tropical fish stock assessment - Part 2: Excercises 1999
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A selection of methods on fish stock assessment is described in detail, with examples of calculations. Special emphasis is placed on methods applicable to tropical fisheries, i.e. those based on the analysis of length-frequencies. After a short introduction to statistics, it covers the estimation of growth parameters and mortality rates, virtual population methods (including length and age based methods), gear selectivity, the yield per recruit model of Beverton and Holt, the estimation of maxim um sustainable yield using surplus production models, multispecies and multifleet problems, the assessment of migratory stocks, a discussion on the stock/recruitment relationship and the execution of demersal trawl surveys. The link between this manual and the length frequency stock assessment (LFSA) package of microcomputer programs is explained. The manual is completed with an extensive list of references (including material for further reading), a list of symbols used, a subject index and a n umber of exercises with solutions. Part 2 gives a number of exercises together with solutions. The exercises are directly related to the various chapters and sections of the manual. -
No Thumbnail AvailableBook (series)Technical studySome simple methods for the assessment of tropical fish stocks 1983This selection of methods is based on lecture notes used at a FAO/DANIDA training course held in Mombasa, Kenya, in May-June 1980. The methods presented are: regression and correlation, estimation of growth parameters from length-frequency data, estimation of mortalities (total, natural, fishing mortality) and analysis of catch and effort data. Only methods that are inherently simple and applicable in the tropics are discussed in detail while more advanced concepts su ch as the distinction between different forms of overfishing, stock-recruitment relationships, multispecies interactions are introduced in the form of an essay. A brief annotated bibliography of tropical fish stock assessment is included.
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Book (series)Technical studyVirtual Population Analysis A Practical Manual for Stock Assessment
A Practical Manual for Stock Assessment
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No results found.Virtual Population Analysis (VPA) is a widely used model for the analysis of fished populations. While there are very many VPA techniques, they vary in the way they use data and fit the model rather than in the form of the model itself. This manual describes the common VPA model and the assumptions on which it is based, together with descriptions of associated diagnostic procedures and common reference points. More importantly, the manual describes the numerical techniques which can be used to f it the model based on weighted least-squares, which is the basis for the ADAPT approach. The techniques are described so that they are readily implemented in a spreadsheet. General methods and specific examples are given to enable the readers to develop an approach suitable for their own data and fisheries.
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LetterLetter from the Acting Secretary, Department of State to D. Lubin, Hotel Raleigh, Washington 1907
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No results found.Asks for the cooperation of the Department of Agriculture and the Department of Commerce and Labor in the formulation of the IIA's plans of work. -
Book (series)Technical studyA third assessment of global marine fisheries discards 2019
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No results found.This third update of FAO’s global discard estimate adopted the ‘fishery-by-fishery’ approach employed in the second discards assessment published in 2005. The update included publicly available discard data in the last 20 years to establish a baseline of a time series of global marine fisheries discards. This is essential for monitoring the status and trends of discard management, which is the first step of the ecosystem approach to fisheries management cycle. In addition, the study developed a new fisheries data table incorporating landings data from the FAO Global Capture Production dataset (FishStat J) from 2010 to 2014, which allocated the landings to over 2 000 fisheries worldwide. The current study estimated that the annual discards from global marine capture fisheries between 2010 and 2014 was 9.1 million tonnes (95% CI: 6.7 – 16.1 million tonnes). About 46 percent (4.2 million tonnes) of total annual discards were from bottom trawls that included otter trawls, shrimp trawls, pair bottom trawls, twin otter trawls and beam trawls. The study included a synthesis of estimates of bycatch and discards of endangered, threatened and protected (ETP) species. Substantial advances have been made in quantifying fisheries interactions with such species so as to make informed decisions on their protection. However, many challenges remain, especially for small-scale fisheries. The development of standardized data collection techniques, risk-based sampling and sharing of data across agencies and regions will help to identify management priorities and allow implementation and enforcement of mitigation measures. A review of previous research showed that discard practices were often related to a wide range of factors, so it is difficult to assess the effectiveness of fishery management actions on the amount and practice of discards. Many regulations are inconsistently enforced, and their implementation is often less strict than intended. Piecemeal approaches in many bycatch and discards management measures can result in unintended cross-taxa conflicts, where regulations designed to reduce bycatch and/or discards of one species or species group may increase bycatch and/or discards of another. Examination of approaches to accounting for and mitigating against pre-catch, post-capture and ghost fishing mortalities demonstrates that an understanding of the relative importance of factors affecting indirect fishing mortality is necessary for estimating total fishing-induced mortality and for designing and implementing mitigation measures.