Larval Fish Assemblages in South-east Australian Coastal Waters: Seasonal and Spatial Structure

Abstract

Seasonal, vertical and horizontal differences in the larval fish assemblages occurring in temperate inner continental shelf waters off Sydney, south-eastern Australia, between December 1989 and February 1993 are assessed and related to the regional oceanography. Carangids, clupeids and bothids numerically dominated the diverse larval fish fauna, which comprised 173 identifiable taxa from 119 families. Assemblages were depth stratified between the surface and mid-water depths of 20–30m during the day in all seasons, with greater numbers of taxa and individuals generally occurring in the mid-water strata. Multivariate analyses showed that there were differences in assemblages sampled at sites 0·5–5km from shore, but there were no consistent cross-shelf (<5km) differences in abundances of larvae, probably because of the dynamic nature of currents in the study region. Recurrent and distinct autumn (April–June), winter (July–August) and spring/summer (September–March) larval fish groups were evident in surface and mid-waters, but these groups were not restricted to any particular oceanographic condition. Membership of the seasonal groups was dynamic as many taxa occurred across more than one season, and some year round. The recurrent nature of the larval groups most likely reflected the temporal coherence of spawning of adults, larval behaviour and interactions with dominant currents.