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Size structural change in lightly exploited coral reef fish communities: Evidence for weak indirect effects

Lookup NU author(s): Dr Nicholas Dulvy, Professor Nick Polunin, Dr Aileen Mill, Nicholas Graham

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Abstract

Exploitation influences community structure directly through preferential removal of larger-bodied fishes and indirectly because larger-bodied fishes may exert top-down control upon other community members. We consider the direct and indirect effects of subsistence exploitation upon the size structure of coral reef fish communities along an island-scale spatial gradient of fishing intensity. We explored the effect of fishing intensity and sample date (three dates over a year) at six islands and the overall effect of fishing intensity averaged over sample dates at 13 islands. Fishing intensity consistently explained more of the variation in the size metrics than sample date. In response to exploitation, the mean weight of individuals declined by 52%, the weighted average maximum size (Lmax) declined by 25%, and slopes of community size spectra steepened. The larger size classes (>26 cm) declined in relative numbers by 63% and relative biomass by 61% in response to exploitation. However, the numbers and biomass of the three smallest size classes (<25 cm) increased by 31% and 9%, respectively, in response to exploitation. This increased abundance is consistent with a weak compensatory response presumably from a reduction in predation upon smaller size classes as an indirect effect of exploiting larger size classes.


Publication metadata

Author(s): Dulvy NK, Polunin NVC, Mill AC, Graham NAJ

Publication type: Article

Publication status: Published

Journal: Canadian Journal of Fisheries and Aquatic Sciences

Year: 2004

Volume: 61

Issue: 3

Pages: 466-475

Print publication date: 01/03/2004

ISSN (print): 0706-652X

ISSN (electronic): 1205-7533

Publisher: NRC Research Press

URL: http://dx.doi.org/10.1139/f03-169

DOI: 10.1139/f03-169


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