ASFB Home > The effects of spatial and temporal factors on the abundance of seven key finfish species along south-western Australia.

Orientation by Reef-Fish Larvae in the Pelagic Environment

Jeff Leis and Brooke M Carson-Ewart

Australian Museum, SYDNEY, AUSTRALIA

THEME: ASFB

During the day, we studied in situ orientation by reef-fish larvae 100-1000m (10-40m depth) from the nearest coral reefs at Lizard Island, Great Barrier Reef: 7 species off the leeward side and 4 of those 7 species off the windward side. All species swam faster than average ambient currents, except one species at one location. Depending on location, time, and species, 80-100% of individual larvae swam directionally. Two species of butterflyfishes (Chaetodon plebeius and C. aureofasciatus) swam away from the island, indicating that they could detect the presence of the island's reefs, although the cues used are unclear. Swimming of four species of pomacentrid damselfishes (Chromis atripectoralis, Chrysiptera rollandi, Neopomacentrus cyanomos and Pomacentrus lepidogenys) ranged from highly directional to non-directional. Only in N. cyanomos did swimming direction differ between windward and leeward areas. Three species (C. atripectoralis, N. cyanomos and P. lepidogenys) were observed in morning and late afternoon on the lee side, and all swam in a more westerly direction in the late afternoon. In the afternoon C. atripectoralis larvae were highly directional in sunny conditions, but non-directional and more variable in cloudy conditions. All this implies pomacentrid larvae utilized a solar compass. One lutjanid (Caesio cuning) was non-directional overall, but its swimming direction differed with distance from the reef. Current direction had no influence on swimming direction. Larvae of different species of reef fishes use different means of orientation while in open, pelagic waters.