Monthly variability of self-recruitment for a coral reef damselfish
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Understanding the dynamics of marine populations is critical to managing marine systems effectively and requires information on patterns of population dispersal and connectivity that are still poorly known. We used transgenerational marking to study larval dispersal of the humbug damselfish, Dascyllus aruanus, in the patchy reef seascape of the southwest Lagoon of New Caledonia (SWL), southwest tropical pacific. The adult population of a patch reef located in the central part of the SWL was injected repeatedly with an enriched 137Ba solution to ensure mass production of marked larvae over two successive reproductive seasons. Multiple cohorts of newly settled larvae were sampled, and their otolith core was analyzed by laser ablation inductively coupled plasma mass spectrometry to assess the seasonal and interannual variability of self-recruitment at the central reef. Connectivity between this reef and ten neighboring reefs was also estimated. Analysis of >1200 settlers indicated that self-recruitment varied significantly between months (ranging from 0 to 68 %) and years (21 % in 2011 and 0 % in 2012). However, variable self-recruitment did not always correspond to variable numbers of self-recruits. Therefore, whereas self-recruitment is undoubtedly a good indication of the degree of population openness, it may not indicate local population persistence. Finally, being the first self-recruitment study to include such a large number of settlers, our study reveals that the threshold used to determine marked individuals significantly affects perceived self-recruitment and connectivity rates and, therefore, must be carefully chosen.
KeywordsDascyllus aruanus Transgenerational marking Otolith Self-recruitment Larval dispersal Connectivity
We thank G. Mou-Tham, J. Tiavouane, D. Grulois, the staff of the scuba diving service, and boat drivers of IRD for assistance with field work, J. Baly, E. Dabas, M. Labonne, G. Lecroizier, J. M. Munaron, and M. Vannereau for assistance with otolith preparation, L. Jamet for assistance with preparation of enriched Barium isotope solution, and F. Foti and the RIEL team of Charles Darwin University for assistance with LA-ICP-MS. We thank D. Starrs and an anonymous reviewer for helpful comments that improved the manuscript. Funding was provided by the COMPO project (Connectivity Of Marine POpulations, www.compo.ird.fr) through a grant from the French National Research Agency (ANR) # 2010 JCJC 1701 01. Ethics and sampling approvals were provided by the Direction du Service de l’Environnement de la Province Sud de Nouvelle-Calédonie, arrêté # 3117-2011/ARR/DENV. This is contribution number 3453 of the Virginia Institute of Marine Science, College of William and Mary.
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