MEPS 145:17-31 (1996)  -  doi:10.3354/meps145017

Meso-scale distribution patterns of larval and pelagic juvenile fishes in the central Great Barrier Reef lagoon

Thorrold SR, Williams DMcB

Larval and pelagic juvenile fish were collected along 2 transects within the central Great Barrier Reef lagoon, Australia, using plankton nets and light traps in October, November and December 1989. Multivariate analyses were used to examine spatio-temporal variability in the distributions of the fish collected with both techniques. Plankton nets revealed a relatively stable cross-lagoon pattern, with (1) a distinctive nearshore component characterized by gobiids, callionymids, leiognathids and teraponids; (2) a cross-lagoon group including nemipterids, carangids, platycephalids and scorpaenids; and (3) an outer-lagoon assemblage dominated by clupeids, lutjanids, pomacentrids, and scombrids. Significant temporal coherence in the abundance patterns of a number of families with cross-lagoon and offshore affinities was also detected. This coherence could have been generated by either a synchronous spawning event, or by hydrographic phenomena acting over synoptic scales of at least 50 km in both alongshore and cross-shelf directions. Light trap catches were much more ephemeral than those from the plankton nets, and were dominated by collections at a single station in October. Numbers of principal taxa at this station were variable on each of the 3 sampling occasions during the month. The most numerous taxa, Pomacentrus spp., were captured in high numbers on all of the 3 nights. Lethrinus spp. and Chromis sp. were abundant on the second night, but low numbers were taken on the first and third nights. Mullids were captured in progressively higher numbers through the sampling period. Comparison of plankton net and light trap data suggested that multi-specific patches of reef fish larvae were characteristic only of late-larval and pelagic juvenile stages. Patch generation may, therefore, be due to active aggregation rather than passive accumulation of larvae. Although the ultimate fate of late-stage larvae within this multi-specific patch was unknown, the data are consistent with the hypothesis that major settlement events occur when occasional dense patches of larvae collide with reef habitats.

Fish larvae · Pelagic juveniles · Plankton nets · Light traps · Spatio-temporal distributions

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