Diel patterns of abundance of presettlement reef fishes and pelagic larvae on a coral reef |
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Authors: | M J Kingsford |
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Institution: | (1) School of Biological Sciences A08, University of Sydney, NSW 2006, Australia e-mail: mikek@bio.usyd.edu.au, AU |
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Abstract: | Most presettlement reef fish settled at night at One Tree Island, Great Barrier Reef. Fish were sampled day and night using
channel nets located on the reef crest, and a plankton-mesh purse-seine net in the lagoon (1992–1994). Catches of fish at
night were generally tens to hundreds of times greater than those taken during the day. Preflexion fish, as well as postflexion
and pelagic juveniles, were taken in greater numbers at night. Preflexion forms were a combination of those that had hatched
from demersal eggs and later stages that had been transported over the reef crest. Highest numbers of postflexion and pelagic
juvenile forms of Apogonidae, Blenniidae, Gobiesocidae, Gobiidae, Labridae, Lutjanidae, Mugiloididae, Mullidae, Pomacentridae,
Scaridae, Serranidae and Tripterygiidae were found at night. Observations, while SCUBA diving, and purse-seine samples in
the lagoon indicated that the only resident larvae were of the genera Spratelloides and Hypoatherina; most of the fishes caught in nets, therefore, were immigrants. Patch reefs, sampled for new settlers early in the morning
and late in the day, indicated that the majority of apogonids (Apogon doederleini, >95%) settled at night. Although greater numbers of pomacentrids were found in morning counts (e.g. Pomacentrus wardi), if data were converted to an hourly rate, many pomacentrids showed a similar hourly rate of settlement day and night. Depth-stratified
sampling in waters near One Tree Island (to 20 m) indicated that some taxa rise to the surface at night. This behaviour, perhaps
combined with avoidance of diurnal predators may explain on-reef movement of potential settlers soon after dark. Studies on
settlement cues, therefore, need to focus on night-related phenomena.
Received: 3 March 2000 / Accepted: 20 June 2000 |
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