Using experiments and expert judgment to model catchability of Pacific rockfishes in trawl surveys, with application to bocaccio (Sebastes paucispinis) off British Columbia

McAllister, Murdock K. and Stanley, Richard D. and Starr, Paul (2010) Using experiments and expert judgment to model catchability of Pacific rockfishes in trawl surveys, with application to bocaccio (Sebastes paucispinis) off British Columbia. Fishery Bulletin, 108(3), pp. 282-304.

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Official URL: http://fishbull.noaa.gov/1083/mcallister.pdf

Abstract

The time series of abundance indices for many groundfish populations, as determined from trawl surveys, are often imprecise and short, causing stock assessment estimates of abundance to be imprecise. To improve precision, prior probability distributions (priors) have been developed for parameters in stock assessment models by using meta-analysis, expert judgment on catchability, and empirically based modeling. This article presents a synthetic approach for formulating priors for rockfish trawl survey catchability (qgross). A multivariate prior for qgross for different surveys is formulated by using 1) a correction factor for bias in estimating fish density between trawlable and untrawlable areas, 2) expert judgment on trawl net catchability, 3) observations from trawl survey experiments, and 4) data on the fraction of population biomass in each of the areas surveyed. The method is illustrated by using bocaccio (Sebastes paucipinis) in British Columbia. Results indicate that expert judgment can be updated markedly by observing the catch-rate ratio from different trawl gears in the same areas. The marginal priors for qgross are consistent with empirical estimates obtained by fitting a stock assessment model to the survey data under a noninformative prior for qgross. Despite high prior uncertainty (prior coefficients of variation ≥0.8) and high prior correlation between qgross, the prior for qgross still enhances the precision of key stock assessment quantities.

Item Type: Article
Title: Using experiments and expert judgment to model catchability of Pacific rockfishes in trawl surveys, with application to bocaccio (Sebastes paucispinis) off British Columbia
Personal Creator/Author:
CreatorsEmail
McAllister, Murdock K.
Stanley, Richard D.
Starr, Paul
Refereed: Yes
Journal or Publication Title: Fishery Bulletin
Volume: 108
Number: 3
Page Range: pp. 282-304
Date: 2010
ISSN: 0090-0656
Issuing Agency: United States National Marine Fisheries Service
Subjects: Biology
Ecology
Fisheries
Item ID: 8746
Depositing User: Patti M. Marraro
Date Deposited: 11 Jun 2012 18:28
Last Modified: 11 Jun 2012 18:28
URI: http://aquaticcommons.org/id/eprint/8746

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