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A test of trophic cascade theory: fish and benthic assemblages across a predator density gradient on coral reefs

Citation

Casey, JM and Baird, AH and Brandl, SJ and Hoogenboom, MO and Rizzari, JR and Frisch, AJ and Mirbach, CE and Connolly, SR, A test of trophic cascade theory: fish and benthic assemblages across a predator density gradient on coral reefs, Oecologia, 183, (1) pp. 161-175. ISSN 0029-8549 (2017) [Refereed Article]

Copyright Statement

Copyright 2016 Springer-Verlag Berlin Heidelberg

DOI: doi:10.1007/s00442-016-3753-8

Abstract

Removal of predators is often hypothesized to alter community structure through trophic cascades. However, despite recent advances in our understanding of trophic cascades, evidence is often circumstantial on coral reefs because fishing pressure frequently co-varies with other anthropogenic effects, such as fishing for herbivorous fishes and changes in water quality due to pollution. Australia’s outer Great Barrier Reef (GBR) has experienced fishing-induced declines of apex predators and mesopredators, but pollution and targeting of herbivorous fishes are minimal. Here, we quantify fish and benthic assemblages across a fishing-induced predator density gradient on the outer GBR, including apex predators and mesopredators to herbivores and benthic assemblages, to test for evidence of trophic cascades and alternative hypotheses to trophic cascade theory. Using structural equation models, we found no cascading effects from apex predators to lower trophic levels: a loss of apex predators did not lead to higher levels of mesopredators, and this did not suppress mobile herbivores and drive algal proliferation. Likewise, we found no effects of mesopredators on lower trophic levels: a decline of mesopredators was not associated with higher abundances of algae-farming damselfishes and algae-dominated reefs. These findings indicate that top-down forces on coral reefs are weak, at least on the outer GBR. We conclude that predator-mediated trophic cascades are probably the exception rather than the rule in complex ecosystems such as the outer GBR.

Item Details

Item Type:Refereed Article
Keywords:community ecology, fishing, herbivory, marine protected areas, top-down effects
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Behavioural Ecology
Objective Division:Environment
Objective Group:Flora, Fauna and Biodiversity
Objective Field:Forest and Woodlands Flora, Fauna and Biodiversity
Author:Rizzari, JR (Dr Justin Rizzari)
ID Code:120319
Year Published:2017
Web of Science® Times Cited:4
Deposited By:Fisheries and Aquaculture
Deposited On:2017-08-22
Last Modified:2017-09-07
Downloads:0

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