The role of Thalassoma lunare as a predator of juvenile fish on a sub-tropical coral reef
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The process of predation causes significant mortality in coral reef fishes immediately following settlement. However, much of what we know of predator identity is based on a small number of detailed studies. This study aims to identify the key predator of early juvenile coral reef fishes on Ningaloo Reef, North-Western Australia. Video cameras were used to observe patch reefs stocked with newly settled reef fish in the back-reef area between 12:00 and 20:30 h. The cameras were fitted with >610 nm light sources to allow observation in low light conditions. All strikes (attempted and successful) on newly settled fish were recorded, along with the time spent in the vicinity of experimental patch reefs with or without juvenile fish. A total of 69 strikes were observed over the 199 h of recorded video footage, with the majority of strikes occurring mid-afternoon between 13:00 and 15:30 h. Only one strike was observed during the twilight period, an hour either side of sunset (~18:45 h), and no strikes were observed after this period. The moonwrasse, Thalassoma lunare, was responsible for the majority of strikes (75.4 %), with the sandperch (Parapercis clatharatha—10.1 %), spanish flag (Lutjanus carponotatus—5.8 %) and ring wrasse (Hologymnosus annulatus—2.9 %) the next highest contributors. T. lunare also spent significantly more time in the vicinity of reefs stocked with newly settled fish, than those without, during daylight hours. The results of the study are in contrast to the common perception that predation on newly settled fish is focused largely around crepuscular periods and suggests that diurnally active species, in particular T. lunare, are important predators of juvenile fish on the Ningaloo back-reef. The study also implies that generalist species can fulfil key functional roles and that the nature of these roles is not always apparent.
KeywordsPredation Recruitment Coral reef fish Ningaloo Thalassoma lunare
We wish to thank the Department of Environment and Conservation Exmouth district staff for their logistical support and field assistance. We also wish to thank Martial Depczynski, Paul Tinkler, Damian Thomson, Ryan Downie and Kylie Cook for their field assistance. This study was conducted through funding supplied by the Department of Environment and Conservation, AIMS, Western Australian Marine Science Institution Node 3, the CSIRO and the Australian National Network in Marine Science internship program.
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