MEPS prepress abstract  -  DOI:

Seagrass meadows shape fish assemblages across estuarine seascapes

Ben L. Gilby*, Andrew D. Olds, Rod M. Connolly, Paul S. Maxwell, Christopher J. Henderson, Thomas A. Schlacher


ABSTRACT: Estuarine seascapes are a mosaic of habitat types that are connected to varying degrees by the movement of organisms. In these seascapes, both the attributes of the habitats themselves as well as the spatial context in which they are embedded can shape faunal assemblages. Here we explicitly test how habitat and connectivity interact to shape fish assemblages across estuaries. Our model system comprised six distinct estuarine habitats (log snags, mangroves, rocky outcrops, seagrass, sand/mud, and urban structures), which represent the full diversity of estuarine habitats and seascape contexts in our study systems. Fish were sampled with cameras at 318 sites in 13 subtropical estuaries in eastern Australia. Habitat type was the principal predictor of fish assemblage composition, an effect that was shaped by spatial connections to other habitats, particularly seagrass beds. Seagrass structured fish assemblages not only by providing a complex habitat that contained more species and individuals than all other habitats, but also by having a ‘footprint’ beyond the edge of meadows. Fish were more diverse and abundant in non-seagrass sites that were closer to seagrass meadows. Two other seascape attributes, proximity of sites to the sea, and to mangroves, also influenced the composition of fish assemblages, albeit less consistently than distance to seagrass. Conservation and fisheries management programs that seek to enhance or restore fish populations in subtropical estuaries should prioritize seagrass conservation initiatives, which encompass critical ecological linkages with other habitats in estuarine seascapes.