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ICES Journal of Marine Science: Journal du Conseil Advance Access originally published online on January 12, 2008
ICES Journal of Marine Science: Journal du Conseil 2008 65(2):255-266; doi:10.1093/icesjms/fsm179
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© 2008 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Standardizing catch rates: is logbook information by itself enough?

J. Bishop1,, W. N. Venables2, C. M. Dichmont3 and D. J. Sterling4

1 20 Tooth Street, Nobby, Queensland 4360, Australia
2 CSIRO Mathematics and Information Science, PO Box 120, Cleveland, Queensland 4163, Australia
3 CSIRO Marine and Atmospheric Research, PO Box 120, Cleveland, Queensland 4163, Australia
4 Trawl Gear Services, 27 Cobble Street, The Gap, Queensland 4061, Australia

Correspondence to J. Bishop: tel: +61 746 963289; fax: +61 746 963289; e-mail: janetbishop{at}bigpond.com

Bishop, J., Venables, W. N., Dichmont, C. M., and Sterling, D. J. 2008. Standardizing catch rates: is logbook information by itself enough? – ICES Journal of Marine Science, 65: 255–266.

The goal of the work was to maximize the accuracy of standardized catch per unit effort as an index of relative abundance. Linear regression models were fitted to daily logbook data from a multispecies penaeid trawl fishery in which within-vessel changes in efficiency are common. Two model-fitting strategies were compared. The predictive strategy focused on maximizing the explained variance, and the estimation strategy on finding realistic coefficients for important components of changing catchability. Realistic values could not always be obtained, because the regression factors were not orthogonal, and data on the presence of technology were sometimes unreliable or systematically incomplete. It was not possible to separate fishing power from abundance by analysing logbook data alone; it was necessary to incorporate external information within the standardization model. Therefore, the resultant estimation models incorporated external information and expert knowledge by offsets. There was no single best estimation model. Instead, a series of models provided an envelope of possible changes in relative fishing power and prawn abundance since 1970. Compared with the prediction models, the estimation models revealed different trends in relative fishing power and relative abundance.

Keywords: catchability, confounding, cpue, expert knowledge, Penaeus, Prawn Trawl Performance Model, shrimp, standardized effort

Received 24 February 2007; accepted 2 November 2007; advance access publication 12 January 2008.


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