Abstract

The natural mechanisms of permanent settlement of marine invertebrates inhabiting rocky intertidal zones (e.g., settlement orientation) are not well known. In this study, we measured the percent covers and densities of two different barnacle species, small-sized Chthamalus challengeri and medium-sized Fistulobalanus albicostatus in a highintertidal zone. Additionally, we analyzed the length/width ratios and orientations of the shells. The four parameters were compared between the two barnacle species. F. albicostatus (mean=49.4 %) showed a similar percent cover as C. challengeri (mean=51.6%) (P=0.915). However, the former species (mean=0.6 inds./cm2) showed a significantly lower density than the latter species (mean=2.8 inds./cm2) (P<0.05). The length and width ratio of F. albicostatus (mean=1.09) was significantly smaller than that of C. challengeri (mean=1.20) (P<0.001). Finally, the settlement orientations of the two species were approximately 0°. The mean settlement angles of F. albicostatus (mean=–2.34°) are smaller than that of C. challengeri (mean=–9.30°), although the difference was not statistically significant (P=0.287). These measurements suggest that the two species, particularly F. abicostatus, tend to avoid strong wave forces with nearvertical settlement angles. In the future, it will be necessary to consider the ideal structure of barnacles against strong wave impacts as a potential target for biomimicry.