Importance of soft canopy structure for labrid fish communities in estuarine mesohabitats

Abstract

Hard structural complexity is widely recognised as important for assessing fish habitat quality, but our understanding of the importance of soft habitat microstructure for temperate marine fishes is less developed. We used best-subsets modelling of underwater surveys in sponge, soft coral, and macroalgae mesohabitats within a temperate estuary to assess what measures of soft habitat structure best predicted differences in wrasse (family: Labridae) fish community composition. We found that significant differences in the labrid fish community among and within mesohabitat types were best explained by a combination of percent canopy cover and soft canopy height, with increased canopy height being correlated with increased fish abundance and species richness. Sponge and macroalgae mesohabitats emerged as particularly important, but vulnerable habitats for a diversity of fishes unique to these mesohabitat types. Ultimately, mesohabitats with high percent canopy cover and height appear to be particularly valuable for supporting estuarine fish communities. Due to this importance, and the potential for decadal-scale recovery times within sponge canopies, we suggest patches with high-quality canopy structure warrant special protection from local threats, such as anchor and fishing damage.