Foragers versus farmers: contrasting effects of two behavioural groups of herbivores on coral reefs

Ceccarelli, Daniela M., Jones, Geoffrey P., and McCook, Laurence J. (2005) Foragers versus farmers: contrasting effects of two behavioural groups of herbivores on coral reefs. Oecologia, 145 (3). pp. 445-453.

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Herbivorous fishes have been attributed a central role in structuring benthic communities on coral reefs. However, the relative importance of different behavioural groups of herbivores may differ and their interactions may be complex. This study focuses on an experiment that discriminates between two groups of herbivorous fish: (1) “Foragers” (relatively mobile, schooling grazers, including parrotfishes and surgeonfishes) and (2) “Farmers” (highly site-attached, territorial species, primarily damselfishes). Preliminary observations at Kimbe Bay (Papua New Guinea) showed that both groups were common, and that farmers defended areas from foragers and maintained algal communities that were distinct from the surrounding undefended substratum. An orthogonal combination of a farmer removal treatment and a forager exclusion treatment was applied to isolate their separate effects on algae and corals, and to determine whether farmer territory composition results from forager exclusion or algal cultivation. The experiment showed that foragers had quantitatively greater and qualitatively different effects on sessile benthic community structure than farmers. Where foragers were excluded, there were substantial increases in the cover and biomass of macro-algae and a decline in some corals, regardless of the presence of farmers. Where farmers were removed there was a moderate decline in the cover of some food algal species, regardless of whether foragers had access. No effect of the exclusion of foragers by farmers could be detected. Our results support prevailing views that foragers have a major impact on coral reefs and farmers cultivate selected algae, but challenge the hypothesis that damselfish influence habitat structure by moderating forager disturbance.

Item ID: 6983
Item Type: Article (Research - C1)
ISSN: 1432-1939
Keywords: benthic algae; territorial damselfish; herbivorous fish; cage experiment
Date Deposited: 16 Feb 2010 03:22
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 80%
05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050102 Ecosystem Function @ 20%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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