Improving Fish Stock Assessments (1998) / Chapter Skim
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Executive Summary
Executive Summary
Pages 1-6
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Techniques of stock assessment range from informal estimates to more sophisticated modeling approaches used to combine data of various types. Assessment models predict rates of change in biomass and productivity based on information about yield from fisheries and the rates at which fish enter the harvestable population (recruitment)
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Committee on Fish Stock Assessment Methods was formed in early 1996 to review existing stock assessment methods and to consider alternative approaches for the future. The committee's statement of task was two-fold: Conduct a scientific review of stock assessment methods and models for marine fisheries management.
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Diminishing the quality of fishery-independent data by failing to modernize NOAA fishery research vessels or by changing sampling methods and gear without proper calibration could reduce the usefulness of existing and future data sets. The simulation study demonstrated that assessments are sensitive to underlying structural features of fish stocks and fishery practices, such as natural mortality, age selectivity, catch reporting, and variations in these or other quantities.
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Despite the uncertainty in stock assessments, fishery scientists may be able to identify robust management measures that can at least prevent overfishing, even if they cannot optimize performance. Conservative management procedures include management tools specific to the species managed, such as minimum biomass levels, size limits, gear restrictions, and area closures (for sedentary species)
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Scientists that conduct stock assessments and organizations that depend on assessments should models; · incorporate Bayesian methods and other techniques to include realistic uncertainty in stock assessment · develop better assessment models for recreational fisheries and methods to evaluate the impacts of the quality of recreational data on stock assessments; · account for effects of directional changes in environmental variables (e.g., those that would accompany climate change) in new models; and · develop new means to estimate changes in average catchability, selectivity, and mortality over time, rather than assuming that these parameters remain constant.
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Education and Training Reduction in the supply of stock assessment scientists would endanger the conduct of fishery assessments by the federal government, interstate commissions, and international management organizations and would hinder progress in the development and implementation of new stock assessment methods. NMFS and other bodies that conduct and depend on fish stock assessments should cooperate to ensure a steady supply of well-trained stock assessment scientists by using mechanisms such as personnel exchanges among universities, government laboratories, and industry and by funding stock assessment research activities.
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