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RESEARCH ARTICLE

The ecological importance of intact top-predator populations: a synthesis of 15 years of research in a seagrass ecosystem

Michael. R. Heithaus A D , A. J. Wirsing B and L. M. Dill C
+ Author Affiliations
- Author Affiliations

A Department of Biological Sciences, School of Environment, Arts and Sciences, Florida International University, 3000 NE 151 Street, North Miami, FL 33181, USA.

B School of Environmental and Forest Sciences, Box 352100, University of Washington, Seattle, WA 98195, USA.

C Evolutionary and Behavioural Ecology Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.

D Corresponding author. Email: heithaus@fiu.edu

Marine and Freshwater Research 63(11) 1039-1050 https://doi.org/10.1071/MF12024
Submitted: 27 January 2012  Accepted: 21 June 2012   Published: 26 November 2012

Abstract

The worldwide decline of large-bodied marine taxa has made it difficult to draw conclusions about the relative importance of top-down control, and the mechanisms through which it might operate, in coastal marine ecosystems. Since 1997, the Shark Bay Ecosystem Research Project has used the relatively pristine seagrass community of Shark Bay, Australia, to investigate the potential for tiger sharks, the apex predator in the ecosystem, to have an impact on their large-bodied prey through non-consumptive (‘risk’) effects. Here, we synthesise nearly 15 years of data to demonstrate that tiger sharks have widespread risk effects on both large-bodied herbivores and mesopredators in Shark Bay and explore the possibility that these impacts may cascade to lower trophic levels. Although much work remains to be done, our studies suggest that losses of top predators in subtropical estuaries may have greater consequences than generally appreciated and that efforts to conserve and restore their populations should be a priority. Furthermore, future management strategies and studies must explicitly consider the potential for predators to influence behaviour of even large-bodied marine taxa.

Additional keywords : behaviourally mediated indirect species interactions (BMII), community dynamics, dugong, Indo‐Pacific bottlenose dolphin, non-consumptive effects, risk effects, tiger shark.


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