Intra- and inter-estuary differences in assemblages of fishes associated with shallow seagrass and bare sand

Abstract

Differences in the assemblages of fishes associated with the seagrass Zostera capricorni and bare sand were assessed across eight estuaries spanning 300 km of the coast of northern New South Wales, Australia. Assemblages consistently differed between habitats in all estuaries, as species affinities within each habitat were relatively consistent. A greater diversity and abundance of fishes generally occurred over seagrass than over sand. Great variation in the abundances of individual species was evident but there were no consistent geographic (inter-estuary) effects. The abundances of most species varied as much between locations (0.5-2.0 km apart) within each estuary as among estuaries (15-300 km apart). Juveniles of economically important species occurred over seagrass (e.g. Rhabdosargus sarba, Acanthopagrus australis, Girella tricuspidata) and sand (e.g. Sillago ciliata). Before the true value of different nursery habitats to fisheries resources can be identified, the contribution of the juvenile fishes residing in the different nursery habitats to future (exploited) populations needs to be quantified.