Distribution and abundance of labrids in northeastern New Zealand: the relationship between depth,exposure and pectoral fin aspect ratio

Physical factors influencing the distribution and abundance of seven common labrid fishes were examined over four rocky reef locations in northeastern New Zealand. Depth and exposure for each species (both within and among sexes) were related to pectoral fin aspect ratio. Each of the four locations (two mainland and two island) displayed distinct labrid assemblages, which were consistent over time, likely due to the influence of the East Auckland Current. There was a consistent depth-related trend for most species, regardless of location. Several species also showed a sex related depth difference. There was also a trend for some species to be associated with certain levels of wave exposure. For most species, the relationship between pectoral fin aspect ratio and the above physical variables was not as strongly evident in this temperate assemblage as has been previously found in tropical reef fish systems. Although some species did follow the predicted shifts in fin aspect ratio with depth and/or exposure, the observed trends were unrelated to fin aspect ratio for many other species. These findings suggest that wave exposure may not be as important for labrids on northeastern New Zealand reefs as it may be in tropical coral reefs systems. The lower fin aspect ratios for New Zealand labrids, compared to tropical labrids, suggest that New Zealand labrids represent a subset of the total pectoral fin diversity in the Labridae. Consequently, the potential for distinct trends in fin aspect ratio and physical variables to be evident may be reduced.