Journal Article

A simulation study of the implications of age-reading errors for stock assessment and management advice

Stuart A. Reeves

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 60, issue 2, pages 314-328
Published in print January 2003 | ISSN: 1054-3139
Published online January 2003 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/S1054-3139(03)00011-0
A simulation study of the implications of age-reading errors for stock assessment and management advice

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Catch-at-age data are a crucial input to many stock assessments, so errors in age determination could have an adverse effect on the quality of the stock assessment and the scientific advice based on that assessment. The results of simulation studies presented in this study are intended to quantify the effects of age-reading errors on the perception of stock trends and short-term management advice. The study is based on Eastern Baltic cod, in which problems with consistent interpretation of otolith structures result in the catch-at-age data being particularly problematic. The results indicate a clear distinction between the performance of the assessment, and the performance of catch forecasts and advice based on that assessment. The ageing error affected the absolute level of estimates of fishing mortality and spawning stock biomass from stock assessments, although overall trends are similar, and general conclusions about the state of the stock are likely to be broadly correct. Greater problems arose in catch forecasts and advice, for which ageing error led to discrepancies between the required and the effective fishing mortality, and a general tendency for ageing error to lead to advice on Total Allowable Catch that would be too optimistic and, therefore, less effective for stock conservation.

Keywords: age-reading errors; Baltic cod; fishery management advice; simulation; stock assessment

Journal Article.  9930 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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