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Sensitivity analysis of terminal year versus three year moving average estimation of survey biomass using an empirical model and a state-space model
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2017
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Description:A simulation study was performed to compare the performance of the previously used empirical assessment model to a state space model for estimating survey biomass using either the terminal year estimate or a three year moving average. An age-structured model of Georges Bank yellowtail flounder was used to evaluate the two models under three future scenarios: no change in biomass, increasing biomass, and decreasing biomass. Each scenario was driven by one of two drivers: recruitment, or fishing. In all scenarios and for both models, the terminal year estimate was found to be more accurate than the three-year average. In addition, the state space model provided more accurate biomass estimates than the empirical model in four out of the five scenarios. The confidence interval for the state space model was generally accurate, but was biased towards underestimating the true confidence interval when biomass was trending up, and overestimating it when biomass was trending down. Similarly, the state space model exhibited a positive retrospective pattern in the declining biomass scenarios, and a negative retrospective pattern in the increasing biomass scenarios. Overall, the largest gains in accuracy were achieved by using the terminal year estimate rather than a three year smooth, and smaller gains were achieved by using the state space model rather than the empirical model.
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Rights Information:Public Domain
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Compliance:Submitted
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