Vertical and horizontal distribution of fish larvae near coral reefs at Lizard Island,Great Barrier Reef

Consistent patterns of horizontal distribution of fish larvae from plankton tows were found in shallow waters around Lizard Island, Great Barrier Reef during 1979 and 1980. Few types of larvae were most abundant in Lizard Lagoon, and none of these were old larvae. Forty percent of the 57 types of larvae studied differed in abundance between windward and downwind sides of the island. More types of old larvae were found in greatest abundance off the windward side of the island than the downwind side. Most types of larvae preferred deeper water (>3 m) during the day and moved upward at night, although a few types preferred upper (<3 m) or middle portions of the water column. These latter were more likely to descend at night or to maintain their day-time distribution than to move upward. Windward larvae [those more abundant off the windward (SE) side of the island] were more shallow-living than were downwind larvae, and were more likely to maintain their day-time distribution at night. The current patterns around Lizard Island were favourable for retention of larvae in both Lizard Lagoon and off the windward side of the island, if combined with certain vertical distributions of the larvae. However, while there was evidence for retention on the windward side of the island, there was no evidence for retention in Lizard Lagoon. Currents on the downwind side of the island were not favourable for retention of larvae and there was little evidence that larvae were retained there. Retention may be an accidental result of interaction between currents and larval behaviour, or the result of a strategy of retention by the larvae. These could not be distinguished in the present study.