Fishing top predators indirectly affects condition and reproduction in a reef-fish community

Authors

  • S. M. Walsh,

    Corresponding author
    1. The Nature Conservancy, 4245 North Fairfax Dr, Suite 100, Arlington, VA 22203-1606, U.S.A.
    2. Environmental Change Initiative, Brown University, Box 1951, Providence, RI 02912, U.S.A.
      Tel.: +1 703 841 2069; email: swalsh@tnc.org
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  • S. L. Hamilton,

    1. Marine Science Institute, University of California, Santa Barbara, CA 91306-6150, U.S.A.
    2. Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, U.S.A.
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  • B. I. Ruttenberg,

    1. Marine Science Institute, University of California, Santa Barbara, CA 91306-6150, U.S.A.
    2. National Marine Fisheries Service, Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami, FL 33149, U.S.A.
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  • M. K. Donovan,

    1. Department of Zoology, University of Hawaii, 2538 McCarthy Mall, Edmondson 165, Honolulu, HI 96822, U.S.A.
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  • S. A. Sandin

    1. Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92083-0202, U.S.A.
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Tel.: +1 703 841 2069; email: swalsh@tnc.org

Abstract

To examine the indirect effects of fishing on energy allocation in non-target prey species, condition and reproductive potential were measured for five representative species (two-spot red snapper Lutjanus bohar, arc-eye hawkfish Paracirrhites arcatus, blackbar devil Plectroglyphidodon dickii, bicolour chromis Chromis margaritifer and whitecheek surgeonfish Acanthurus nigricans) from three reef-fish communities with different levels of fishing and predator abundance in the northern Line Islands, central Pacific Ocean. Predator abundance differed by five to seven-fold among islands, and despite no clear differences in prey abundance, differences in prey condition and reproductive potential among islands were found. Body condition (mean body mass adjusted for length) was consistently lower at sites with higher predator abundance for three of the four prey species. Mean liver mass (adjusted for total body mass), an indicator of energy reserves, was also lower at sites with higher predator abundance for three of the prey species and the predator. Trends in reproductive potential were less clear. Mean gonad mass (adjusted for total body mass) was high where predator abundance was high for only one of the three species in which it was measured. Evidence of consistently low prey body condition and energy reserves in a diverse suite of species at reefs with high predator abundance suggests that fishing may indirectly affect non-target prey-fish populations through changes in predation and predation risk.

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