Vertical distribution and ontogenetic "migration" in coral reef fish larvae

Irisson, Jean-Olivier, Claire B. Paris, C├ędric Guigand, Serge Planes

Limnol. Oceanogr., 55(2), 2010, 909-919 | DOI: 10.4319/lo.2010.55.2.0909

ABSTRACT: Vertical distribution patterns were studied in the community of coral reef fish larvae around Tetiaroa (French Polynesia) using vertically stratified net tows within the first 100 m of the water column. These patterns were examined statistically using an approach based on the center of mass of larval patches. Regression trees first highlighted large differences between taxa, followed by an ontogenetic effect within each taxon. Many families displayed a vertical spread during ontogeny that accounted in part for a downward shift in the distribution of centers of mass. The spread suggests that, throughout ontogeny, individuals move within a wider range of depths rather than migrate downward synchronously. Both the spread and the shift were consistent at the community level despite the taxonomic differences. No difference in mean depth or spread was discernible between day and night, except for Serranidae, which were shallower at night. Environmental factors (such as thermocline depth or current shear) usually explained little variance, except for Lethrinidae and Blennidae, which were consistently deeper when the halocline was deeper. Although the overall effect of the observed ontogenetic spread in such a mildly stratified environment is likely to be small, it might still favor exceptional cases of retention, which can be important given the very low recruitment rate of coral reef fishes.

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