Stock Assessment for Fishery Management: A Framework Guide to the stock assessment tools of the Fisheries Management Science Programme.

Abstract

This paper provides 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) in the years 1992 to 2004. Part 1 describes some key elements of the precautionary approach to fisheries management. A stock assessment process is also outlined that can provide the information needed for such precautionary management. The management process summarized in Chapter 2 is based on recent FAO guidance, including the Code of Conduct for Responsible Fisheries. It emphasizes the need for setting goals and operational objectives; for defining these explicitly as reference points for a range of fishery indicators; for adopting decision control rules that include precautionary thresholds allowing for uncertainties and risk tolerances, and that drive fishery management using a set of measures that are pre-agreed with stakeholders. Chapter 2 also stresses the need to integrate use rights and co-management arrangements into the management framework, where appropriate, as key elements for success.

Chapter 3 presents the process of stock assessment, underlining the need for quantitative assessment of uncertainties and risks and the provision of advice based on the various goals of the fishery and considering both short- and long-term impacts of management strategies. Methods are given to estimate the current status of the fishery either as the stock size, the fishing mortality rate or other ecological or goal-based indicators. Methods are also described for estimating maximum sustainable yield (MSY) and other yield-based reference points, as well as some aimed at protecting the spawning capacity of the stock and avoiding recruitment overfishing. For sustainable exploitation, it is recommended that yield-based reference points are used as targets while spawning capacity reference points are used as limits and given the higher precedence. Precautionary thresholds should be set to prevent the limits being exceeded.

Chapter 4 provides information on the FMSP stock assessment tools and guidelines, including four FMSP software packages - LFDA, CEDA, Yield and ParFish - by which intermediate parameters, indicators and reference points may be estimated. The inputs and outputs and the relative advantages and potential uses of the tools are described. The four chapters in Part 2 further describe these four software tools, providing guidelines on their use and the fitting of models. Full technical details and tutorials are available in the software help files provided on the accompanying CD-ROM.

Part 3 then summarizes the guidelines produced by a number of other FMSP projects relating to stock assessment and management approaches that were introduced in Chapter 4. Chapter 10 uses simulation models to compare the performance of lengthbased and age-based approaches for two tropical fish species. The analysis demonstrates the benefits of using age based approaches where possible, but it is noted that results may differ for other species and their particular life history strategies. Chapter 11 develops simple relationships for the estimation of potential yield and maximum sustainable fishing mortality based on the Beverton and Holt \"life-history invariants\". These relationships allow sustainable yields and fishing capacity to be estimated from sparse data, which may either be already available, or can be relatively easily obtained. Chapter 12 derives guidelines for the management of multispecies demersal bank and deep reef slope fisheries exploited principally with hooks and lines. Chapter 13 presents a Bayesian stock assessment applied to the Namibian orange roughy fishery. This case study illustrates the benefits and some of the difficulties found in applying the Bayesian approach and draws out some lessons learnt. Chapter 14 describes

Citation

FAO Fisheries Technical Paper No. 487, FAO, Rome, Italy, ISBN 92-5-105503-3, 261 pp.

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