Temperate zone coastal seascapes: seascape patterning and adjacent seagrass habitat shape the distribution of rocky reef fish assemblages

Context Whilst the composition and arrangement of habitats within landscape mosaics are known to be important determinants of biodiversity patterns, the influence of seascape patterning and connectivity on temperate reef fish assemblages remains largely unknown. Objectives We examined how habitat patterns at multiple spatial scales (100-1000 m) explained the abundance and diversity of temperate reef fish in a reef-seagrass dominated seascape. Methods Fish assemblages were surveyed using remote underwater videos deployed on 22 reefs in Jervis Bay, NSW, Australia. Using full-subset GAMMs, we investigated if habitat area, edge, structural connectivity and a metric for habitat diversity (Shannon's diversity index) of reef and seagrass can predict variations in a temperate reef fish assemblage. Results A key finding of the study was that temperate reefs close (< 55 m) to large (> 6.25 ha) seagrass meadows contained greater abundance and diversity of fish. A consistent negative correlation was also found between reef area (> 0.01 ha) and the fish assemblage. The influence of seascape metrics on the abundance of fishes varied with functional traits (trophic groups, mobility and habitat associations). Fish-seascape relationships occurred at a range of spatial scales with no single scale being solely important for structuring the fish assemblage. Conclusions We demonstrate that it is important not to view reef habitats in isolation, rather consider a reefs context to adjacent seagrass when predicting the distribution of temperate reef fish. This finding improves current understanding of the multi-scale factors structuring temperate reef fish assemblages and highlights the importance of reef-seagrass connectivty for the management of temperate marine ecosystems.