Journal Article

Using size-based indicators to evaluate the ecosystem effects of fishing

Yunne-Jai Shin, Marie-Joëlle Rochet, Simon Jennings, John G. Field and Henrik Gislason

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 62, issue 3, pages 384-396
Published in print January 2005 | ISSN: 1054-3139
Published online January 2005 | e-ISSN: 1095-9289 | DOI:
Using size-based indicators to evaluate the ecosystem effects of fishing

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  • Environmental Science
  • Marine and Estuarine Biology


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The usefulness and relevance of size-based indicators (SBIs) to an ecosystem approach to fisheries (EAF) are assessed through a review of empirical and modelling studies. SBIs are tabulated along with their definitions, data requirements, potential biases, availability of time-series, and expected directions of change in response to fishing pressure. They include mean length in a population, mean length in a community, mean maximum length in a community, and the slope and intercept of size spectra. Most SBIs can be derived from fairly standard survey data on length frequencies, without the need for elaborate models. Possible fishing- and environment-induced effects are analysed to distinguish between the two causes, and hypothetical cases of reference directions of change are tabulated. We conclude that no single SBI can serve as an effective overall indicator of heavy fishing pressure. Rather, suites of SBI should be selected, and reference directions may be more useful than reference points. Further modelling and worldwide comparative studies are needed to provide better understanding of SBIs and the factors affecting them. The slow response to fishing pressure reflects the complexity of community interactions and ecosystem responses, and prohibits their application in the context of short-term (annual) tactical fisheries management. However, movement towards longer-term (5–10 years) strategic management in EAF should facilitate their use.

Keywords: ecosystem approach to fisheries; size-based indicators; size spectrum

Journal Article.  8340 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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