Journal Article

Using survey data independently from commercial data in stock assessment: an example using haddock in ICES Division VIa

D.J. Beare, C.L. Needle, F. Burns and D.G. Reid

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 62, issue 5, pages 996-1005
Published in print January 2005 | ISSN: 1054-3139
Published online January 2005 | e-ISSN: 1095-9289 | DOI: https://dx.doi.org/10.1016/j.icesjms.2005.03.003
Using survey data independently from commercial data in stock assessment: an example using haddock in ICES Division VIa

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Currently standard fish stock biomass estimates are based most directly on commercial catch-at-age data. The main contribution made by research-vessel trawl survey data to the stock assessment process is to “tune” trends in the commercial data and provide estimates of incoming year-class strength. In this process much of the information contained with the survey data (e.g. spatial detail) is lost because the data are first aggregated into numbers-at-age indices for given areas. Another problem is that increasingly restrictive total allowable catches (TACs) imposed on the fishing industry have led to what is suspected to be widespread misreporting, i.e. the scientists do not know how many fish have been landed. This leads to negative biases in the catch data, low stock abundance estimates by scientists, even lower TACs, followed by even more misreporting. One potential way to escape this downward spiral is to explore scientific trawl survey data in more detail since trawl surveys are more straightforward to regulate. Traditionally, there has been resistance to this idea since, in comparison to commercial catch-at-age data, trawl survey data are very sparse in space and time. In this study, the potential for using trawl survey data independently in stock assessments is explored for the case of ICES Area VIa haddock, using two different tools. Findings suggest that it is possible to get qualitatively useful information from trawl survey data alone as well as quantitative, spatially resolved, estimates of fish abundance by making simple swept-area assumptions. In addition, interesting differences between survey and commercial data are highlighted by the study. The mean age of fish reported by the commercial fleet, for example, is higher than that reflected by the survey data, while fishing mortality estimates tend to be higher when estimated from survey data alone.

Keywords: fisheries stock assessment; research-vessel survey data; spatio-temporal assessment; survey-based assessment; time-series analysis

Journal Article.  4197 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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