MEPS 252:207-222 (2003)  -  doi:10.3354/meps252207

Fine-scale temporal and spatial patterns of larval supply to a fringing reef in Western Australia

J. L. McIlwain1,2,*

2Australian Institute of Marine Science, PO Box 83, Fremantle 6959, Western Australia, Australia
2Present address: Department of Marine Science & Fisheries, Sultan Qaboos University, PO Box 34, Al-Khod 123, Sultanate of Oman

ABSTRACT: The abundance and diversity of larval fish entering the lagoon of Ningaloo Reef, Western Australia, was monitored every day over a 4 to 5 mo period for each of 2 consecutive summers. This was done by deploying reef crest nets in the surf zone to capture the larvae making the transition from the pelagic environment to the lagoon. In the first summer, 2 nets 500 m apart were deployed for 94 nights. In the second summer, these same nets were redeployed in the same location along with an additional pair located 5 km to the south. These 4 nets were deployed for 101 nights. A total of 89598 presettlement fish from 65 families/groups was caught over both years with most fish coming from the Gobiidae, Blennidae, Labridae, Apogonidae and Lutjanidae families. Fewer larvae were caught in the second summer compared to the first. For both summers, the majority of the catch arrived during November and December, with abundance declining gradually as the season progressed. To examine periodicity in arrival, time series analysis was performed on 25 of the most abundant families/taxa. Larvae from different families and with entirely different morphologies arrived on a semi-lunar basis, such as the leptocephali, labrids and scorpaenids, whilst others arrived during cycles of less than 30 d (soles), approximately 28 d (leptocephali), greater than 30 d (Omobranchini blennies) and stochastically (some gobies, apogonids and labrids). Cross-correlation techniques were used to compare differences in abundance at 2 spatial scales: 5 km and 500 m. I found multi-specific patches of larvae at least 5 km wide crossing the reef crest into the lagoon habitat. The timing of these patches was often chaotic and rarely lasted longer than 24 h. I found that reef crest nets were an appropriate sampling tool for Ningaloo Reef, catching a rich assemblage of presettlement fish rarely seen on Australian coral reefs. I compare larval replenishment patterns at Ningaloo with other studies from the Caribbean, Central Pacific, Bahamas and eastern Australia, and discuss the importance of continuing to monitor larval assemblages at new locations preferably using modified, fixed plankton nets.

KEY WORDS: Larval supply · Coral reef fish · Recruitment · Ningaloo · Settlement · Lunar periodicity · Crest nets

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