Publication Abstract

Coral reef catastrophes, starfish outbreaks and reduced ecosystem resilience result from predator removal

N.K. Dulvy, R.P. Freckleton and N.V.C. Polunin

Drastic changes in community composition leading to phase shifts and alternate ecosystem states have long been of interest to ecologists. Phase shifts may be key to understanding the effects of exploitation on species-diverse ecosystems. We show that coral reef phase shifts may result from subsistence levels of exploitation. Ecosystem state was measured along an island-scale gradient of fishing pressure in Fiji. The density of a keystone coral-feeding starfish (Acanthaster planci) increased along the fishing gradient resulting in large-scale mortality of reef-building corals and subsequent phase shifts. Predatory fish density declined in response to exploitation suggesting the starfish, checked by a predator-controlled Allee effect at the most lightly fished islands, is released from predatory control even by subsistence levels of exploitation. A simple predator-prey model shows how exploitation can reduce coral-reef ecosystem resilience.

Reference:

N.K. Dulvy, R.P. Freckleton and N.V.C. Polunin (2004) Coral reef catastrophes, starfish outbreaks and reduced ecosystem resilience result from predator removal. Ecology Letters, 7: 410-416