Small-scale spatial and temporal variability of larval fish assemblages at an isolated oceanic island

This study investigated the small-scale spatial distribution and temporal variability of larval fish assemblages at Saint Paul's Rocks along the Mid-Atlantic Ridge. Larvae were collected during 8 expeditions in 2003, 2004 and 2005 from surface horizontal plankton samples at different distances around the archipelago and inside a cove located between the main islets. Identification resulted in 80 taxa distributed across 29 families; 72 taxa represented individual species. Myctophidae was the most diverse family, followed by Gonostomatidae. The larvae of reef fish, such as the endemic damselfish Stegastes sanctipauli and the blenny Entomacrodus vomerinus, were most abundant. Pelagic fish larvae were also common in the samples, but at low abundances. Reef fish larvae were also the most abundant and frequent in the cove, while at distances up to 500 m and >500 m from the islets, larvae of pelagic species such as the lanternfishes Ceratoscopelus warmingii and Lampadena luminosa, and the flyingfish Oxyporhamphus micropterus were more representative. Cluster analysis superimposed on a non-metric multidimensional scaling indicated 4 significantly different groups (SIMPROF, p < 0.05) within the samples. Indicator species analysis revealed 4 fish larvae assemblages in the surface layer: a reef assemblage, a neritic assemblage, a nighttime oceanic assemblage and a daytime oceanic assemblage. Our findings illustrate the distribution of fish larvae that inhabit the surface waters around Saint Paul's Rocks and provide information about the temporal variability in larval abundance of some reef and pelagic species.