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Body size-dependent responses of a marine fish assemblage to climate change and fishing over a century-long scale

Authors

  • MARTIN J. GENNER,

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
    2. School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
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  • DAVID W. SIMS,

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
    2. Marine Biology and Ecology Research Centre, School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK
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  • ALAN J. SOUTHWARD,

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
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    • Deceased 27 October 2007.

  • GEORGINA C. BUDD,

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
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  • PATRICIA MASTERSON,

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
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  • MATTHEW MCHUGH,

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
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  • PETER RENDLE,

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
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  • EMILY J. SOUTHALL,

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
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  • VICTORIA J. WEARMOUTH,

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
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  • STEPHEN J. HAWKINS

    1. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
    2. College of Natural Sciences, Memorial Building, Bangor University, Gwynedd LL57 2UW, UK
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M. J. Genner, School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK, tel. +44 117 928 9827, fax +44 117 331 7985, e-mail: m.genner@bristol.ac.uk

Abstract

Commercial fishing and climate change have influenced the composition of marine fish assemblages worldwide, but we require a better understanding of their relative influence on long-term changes in species abundance and body-size distributions. In this study, we investigated long-term (1911–2007) variability within a demersal fish assemblage in the western English Channel. The region has been subject to commercial fisheries throughout most of the past century, and has undergone interannual changes in sea temperature of over 2.0 °C. We focussed on a core 30 species that comprised 99% of total individuals sampled in the assemblage. Analyses showed that temporal trends in the abundance of smaller multispecies size classes followed thermal regime changes, but that there were persistent declines in abundance of larger size classes. Consistent with these results, larger-growing individual species had the greatest declines in body size, and the most constant declines in abundance, while abundance changes of smaller-growing species were more closely linked to preceding sea temperatures. Together these analyses are suggestive of dichotomous size-dependent responses of species to long-term climate change and commercial fishing over a century scale. Small species had rapid responses to the prevailing thermal environment, suggesting their life history traits predisposed populations to respond quickly to changing climates. Larger species declined in abundance and size, reflecting expectations from sustained size-selective overharvesting. These results demonstrate the importance of considering species traits when developing indicators of human and climatic impacts on marine fauna.

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