Coral Reefs

, Volume 31, Issue 2, pp 547–559

Indirect consequences of fishing: reduction of coralline algae suppresses juvenile coral abundance

  • J. K. O’Leary
  • D. C. Potts
  • J. C. Braga
  • T. R. McClanahan
Report

DOI: 10.1007/s00338-012-0872-5

Cite this article as:
O’Leary, J.K., Potts, D.C., Braga, J.C. et al. Coral Reefs (2012) 31: 547. doi:10.1007/s00338-012-0872-5

Abstract

Removing predatory fishes has effects that cascade through ecosystems via interactions between species and functional groups. In Kenyan reef lagoons, fishing-induced trophic cascades produce sea urchin-dominated grazing communities that greatly reduce the overall cover of crustose coralline algae (CCA). Certain species of CCA enhance coral recruitment by chemically inducing coral settlement. If sea urchin grazing reduces cover of settlement-inducing CCA, coral recruitment and hence juvenile coral abundance may also decline on fished reefs. To determine whether fishing-induced changes in CCA influence coral recruitment and abundance, we compared (1) CCA taxonomic compositions and (2) taxon-specific associations between CCA and juvenile corals under three fisheries management systems: closed, gear-restricted, and open-access. On fished reefs (gear-restricted and open-access), abundances of two species of settlement-inducing CCA, Hydrolithon reinboldii and H. onkodes, were half those on closed reefs. On both closed and fished reefs, juveniles of four common coral families (Poritidae, Pocilloporidae, Agariciidae, and Faviidae) were more abundant on Hydrolithon than on any other settlement substrate. Coral densities were positively correlated with Hydrolithon spp. cover and were significantly lower on fished than on closed reefs, suggesting that fishing indirectly reduces coral recruitment or juvenile success over large spatial scales via reduction in settlement-inducing CCA. Therefore, managing reefs for higher cover of settlement-inducing CCA may enhance coral recruitment or juvenile survival and help to maintain the ecological and structural stability of reefs.

Keywords

Trophic cascades Crustose coralline algae Coral settlement Early life history Hydrolithon Sea urchins 

Supplementary material

338_2012_872_MOESM1_ESM.tif (635 kb)
Appendix Figure 1: Observed (open bars) versus expected (solid bars) numbers of juvenile corals associated with suitable settlement substrate categories (CCA, bare, and turf-dominated) on each of nine reef from three management systems. χ2 results are shown where expected sample sizes were >5. (TIFF 635 kb)
338_2012_872_MOESM2_ESM.tif (759 kb)
Appendix Figure 2: Observed (open bars) versus expected (solid bars) numbers of juvenile corals associated with the five identifiable CCA taxa on each of nine reefs sites under three management systems. χ2 results are shown where expected sample sizes were >5. (TIFF 759 kb)

Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • J. K. O’Leary
    • 1
  • D. C. Potts
    • 1
  • J. C. Braga
    • 2
  • T. R. McClanahan
    • 3
  1. 1.Department of Ecology and Evolutionary BiologyUniversity of CaliforniaSanta CruzUSA
  2. 2.Departamento de Estratigrafía y PaleontologíaUniversidad de GranadaGranadaSpain
  3. 3.Marine ProgramsWildlife Conservation SocietyBronxUSA

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