Variability in the trophic role of coral reef fish larvae in the oceanic plankton

The transport of larval coral reef fishes to juvenile habitat inherently requires that they survive the planktonic journey; however, the processes governing survival-particularly those related to feeding-are not well known. Monthly sampling across the Straits of Florida allowed for analyses of the diets and diet variability of several co-occurring taxa of coral reef fish larvae from the families Serranidae, Lutjanidae, Mullidae, Pomacentridae, Labridae, Scaridae and Acanthuridae. The proportions of larvae with food present in the gut were high (0.94 to 1.0) for all taxa except scarids (0.04), and diets were generally narrow and predator-specific. Serranus spp. (Serranidae) diets changed little with growth and were composed almost entirely of calanoid copepods, while the labrids Thalassoma bifasciatum and Xyrichtys spp. consumed harpacticoid and cyclopoid (Farranula and Oncaea) copepods almost exclusively throughout ontogeny. Lutjanine and acanthurid larvae relied increasingly upon appendicularians with growth, and mullids exhibited an ontogenetic shift from nauplii to calanoid copepodites and appendicularians, Cluster analysis examining diet similarity among taxa yielded clear groupings: small acanthurids, labrids, appendicularian-feeders, and a fourth group consisting of subgroups of larvae with calanoid and mixed diets, Within larval taxa, canonical correspondence analysis indicated how diet varied with several environmental and larva-specific variables. The trophic niche breadth of 4 taxa decreased significantly with growth, while other taxa exhibited no significant change. These results highlight distinct differences between high- and low-latitude regions, most notably the taxon-specific trophic roles and the apparent niche partitioning of larval fishes within the diverse planktonic food webs of lower latitudes.