Wave exposure, swimming performance, and the structure of tropical and temperate reef fish assemblages

We examined the relationship between swimming performance, wave exposure, and the distribution patterns of labrids on temperate rocky reefs, in comparison with previous functional analyses of a tropical assemblage. Visual censuses of the distribution and abundance of labrids across two major gradients of wave exposure (depth and aspect to prevailing winds) were made at two offshore islands near Port Stephens, New South Wales, Australia. Distinct shifts in species composition and abundance were evident between high and low wave exposure habitats on temperate rocky reefs, particularly between deep and shallow habitats on exposed reef fronts. The swimming performances of temperate labrids were assessed through examination of pectoral fin shape (aspect ratio) and in situ swimming speeds. A diversity of pectoral fin morphologies was exhibited within this temperate assemblage, ranging from rounded to tapered fins (aspect ratios of 0.52 and 1.43, respectively). Fin shape was strongly correlated (Pearsonrsquos correlation 0.884, P