The Rabbitfish <i>Siganus virgatus</i> as Key Macroalgae Browser in Coral Reefs of the Gulf of Thailand
2021
Malika Müller | Constanze F. K. Staab | Laura D. Puk | Eike M. Schoenig | Sebastian C. A. Ferse | Christian Wild
Coral reef resilience is greatly influenced by herbivory. There is a need to identify key fish species fulfilling this critical function in biogeographically distinct regions. This experimental in situ study investigated fish herbivory in coral reefs of the lower Gulf of Thailand characterized by a considerably low herbivorous fish biomass and diversity, but high live coral and low macroalgal cover. This provided an intriguing situation for macroalgal browsing research. Visual census techniques assessed the abundance of local herbivorous fish species, and filmed single-choice assays using the macroalga <i>Turbinaria</i> evaluated mass-standardized bites (ms-bites) and biomass removal. Multiple-choice assays offering four locally abundant macroalgae identified specific biomass removal and ms-bites to uncover selection and avoidance patterns of observed fish species. The rabbitfish <i>Siganus</i><i>virgatus</i> constituted only 39% of herbivore biomass but accounted for 90% of ms-bites. In multiple-choice assays, fishes took most (61%) bites on <i>Sargassum</i>, followed by <i>Padina</i> (28%) and <i>Turbinaria</i> (11%), while <i>Lobophora</i> was avoided. <i>S. virgatus</i> exhibited the most generalized browsing pattern of all species observed. Coinciding with recent studies, our findings suggest that <i>S. virgatus</i> plays a key functional role in reefs characterized by low diversity of herbivores and low functional redundancy.
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