Abundance patterns of subtidal benthic invertebrates and fishes at the Kermadec Islands

Abstract

Vertical distributions of benthic fauna and fish are described for a number of sites at the subtropical Kermadec Islands (30°S, 178°W). Six sites throughout the entire group were quantitatively sampled, samples consisted of timed counts (for benthic and pelagic fish) or quadrat counts (for mobile benthic invertebrates) at various water depths. Ten species of mobile benthic invertebrates were identified in quadrats. The endemic limpet Patella kermadecensis was confined to shallow water at all sites. The echinoid Heliocidaris tuberculata was also abundant in depths less than 9 m, while Centrostephanus rodgersii was most abundant at greater depths. Twelve species of fish were identified in pelagic counts. There was some depth stratification in the abundances of pelagic fish: Labracoglossa nitida, Bathystethus cultratus, and Kyphosus bigibbus were all more abundant in counts shallower than 10 m, while Chromis dispilus was more abundant at greater depths. Thirty-four species of fish were identified in benthic counts. Most showed no consistent depth-related trends, but Aplodactylus etheridgii and Stegastes fasciolatus were more abundant in shallow water, while Chrysiptera rapanui was most abundant in the deep stratum. Our data support previously described patterns of vertical distribution of the marine fauna at the Kermadec Islands, and suggest that the abundances of herbivores are insufficient to account for the lack of macroalgae. Further, we suggest that more detailed studies in subtropical regions may provide a better understanding of the fundamental differences between temperate and tropical reefs.