Diel changes in vertical distributions of larval fishes in unstratified coastal waters off southeastern Australia

Abstract

Larval fishes were sampled at four depth strata during the day and night at two locations in unstratified (winter) inner continental shelf waters off Sydney, Australia, in May and June 1993. Assemblages at both locations and in both sampling periods were strongly depth stratified during the day; however, this structure weakened at night with most taxa being found throughout the entire water column. Two daytime patterns of larval fish vertical distribution (surface and deep dwellers) were evident, and taxon-specific daytime vertical distributions were strong and not dependent on thermal stratification of the water column. Most larvae caught were preflexion and there was little evidence of ontogenetic differences in vertical distributions. For most taxa, the patterns of diel change in vertical distribution were similar at both locations and in both sampling periods.