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

Type Article
Date 2005-05
Language English
Author(s) Shin Yunne-Jai1, Rochet Marie-Joelle2, Jennings Simon3, Field John4, Gislason Henrik5
Affiliation(s) 1 : IRD, CHRMT Thetis, F-34203 Sete, France.
2 : IFREMER, Lab MAERHA, F-44311 Nantes, France.
3 : CEFAS, Lowestoft Lab, Lowestoft NR33 0HT, Suffolk, England.
4 : Univ Cape Town, Dept Zool, ZA-7701 Rondebosch, South Africa.
5 : Danish Inst Fisheries Res, DK-2920 Charlottenlund, Denmark.
Source ICES Journal of Marine Science (1054-3139) (Elsevier), 2005-05 , Vol. 62 , N. 3 , P. 384-396
DOI 10.1016/j.icesjms.2005.01.004
WOS© Times Cited 343
Keyword(s) Size spectrum, Size based indicators, Ecosystem approach to fisheries
Abstract 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.
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