Fish predation on sea urchins on the Great Barrier Reef

Young, M.A.L., and Bellwood, D.R. (2012) Fish predation on sea urchins on the Great Barrier Reef. Coral Reefs, 31 (3). pp. 731-738.

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Abstract

Predators are important for regulating adult sea urchin densities. Here, we employ remote underwater video cameras to record diurnal predation on tethered sea urchins at Lizard Island on the Great Barrier Reef (GBR). We identified four fish predators of adult sea urchins (Balistoides viridescens, Balistapus undulatus, Lethrinus atkinsoni and Choerodon schoenleinii). Predator activity appeared to be site-specific. Balistoides viridescens and B. undulatus (f: Balistidae) were the two most important predators of Echinometra mathaei with the former handling E. mathaei significantly faster (mean 0.7 min) than B. undulatus (5.2 min). Balistoides viridescens also successfully preyed on 70 % of detections, while C. schoenleinii, B. undulatus and L. atkinsoni preyed on just 33, 17 and <1 %, respectively. Additionally, B. viridescens were behaviourally dominant among predator species and were observed as aggressors in 30 encounters with B. undulatus and 8 encounters with L. atkinsoni. In only one encounter was B. viridescens the recipient of any aggression (from B. undulatus). In terms of relative vulnerability, of the three sea urchin species examined, E. mathaei were more vulnerable to predation than Diadema setosum or Echinothrix calamaris, with mean handling times of 1.2, 4.8 and 10.3 min, respectively. Balistoides viridescens and B. undulatus both appear to be able to play an important role as predators of sea urchins on the relatively intact coral reefs of Lizard Island. However, B. viridescens emerge as the most efficient predator in terms of handling speed and the proportion of detections preyed upon. They were also the behaviourally dominant predator. This preliminary study of the predators of sea urchins on the GBR highlights the potential significance of relatively scarce but functionally important species.

Item ID: 24641
Item Type: Article (Refereed Research - C1)
Keywords: sea urchin, predation, coral reefs, triggerfish, tethering, Echinometra mathaei
ISSN: 1432-0975
Date Deposited: 22 Jan 2013 02:52
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 50%
05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050102 Ecosystem Function @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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