In situ swimming speeds of the late pelagic larvae of some Indo-Pacific coral-reef fishes

Swimming speeds of the late-stage, pelagic larvae of coral-reef fishes were measured in situ near Lizard Island on Australia's Great Barrier Reef, and Rangiroa Atoll, Tuamotu Islands, French Polynesia during 1995-96. Larvae were captured with light traps End crest nets, and released individually in open water. They were then followed by SCUBA divers, normally for 10 min, and their speed was measured with a modified plankton-net flow meter and a stop watch. Swimming speeds of 260 larvae of 50 species in 15 families of mostly perciform reef fishes are presented. Most measurements were for pomacentrids (8 genera, 16 species, 127 individuals), apogonids (1 genus, similar to 5 species, 18 individuals), chaetodontids (3 genera, 8 species, 49 individuals), lethrinids (1 genus, similar to 4 species, 11 individuals), nemipterids (1 genus, 2 species, 10 individuals), serranids (2 genera, 2 species, 14 individuals) and acanthurids (2 genera, similar to 4 species, 13 individuals). Numbers of individuals per species ranged from 1 to 25. Speeds were remarkably high for such small fishes (0.7 to 5.5 cm). Average speed was 20.6 cm s(-1) (range 2 to 65), or 13.7 body lengths s(-1) (range 2 to 34). SE for species with n > 4 ranged from 0.8 to 5.3 cm s(-1) (4.1 to 25.0% of mean speed), but speed of the fastest individual of each species averaged 144% of mean speed. A taxonomic component was evident, with apogonids the slowest (2 to 13 cm s(-1)), followed by nemipterids (10 cm s(-1)). Speed of pomacentrids and chaetodontids varied widely among species (7 to 35 cm s(-1)), whereas acanthurids, lethrinids and serranids were fast (19 to 55 cm s(-1)). Except for apogonids and nemipterids, nearly all species had mean swimming speeds greater than average ambient current speeds in the Lizard island area. Mean speed was positively correlated with size (slope 8.2, r(2) = 0.43) when all taxa were included, but was not correlated with size for the Pomacentridae and Chaetodontidae when each were considered alone. The speeds reported here combined with data on swimming endurance recently reported by Stobutzki & Bellwood (1997; Mar Ecol Prog Ser 149:35-41) reveal remarkable swimming abilities for late-stage pelagic larvae of coral-reef fishes which could either greatly enhance dispersal or eliminate it.