Ranking of settlement cues by barnacle larvae: Influence of surface contour

Plastic models of adult and juvenile barnacles were used to test the consistency of response of settling barnacle larvae to surface contour cues. Three sets of three casts from the same mould were placed in the intertidal zone and exposed to settlement by Chthamalus fragilis and Semibalanus balanoides larvae. Larvae tended to settle in identical locations on replicate casts from the same mould. As many as 30% of the larvae settled in the same microsites on replicate surfaces. The proportion of attractive sites is about 7% of the total area available for settlement. Flume experiments indicate that attractive sites tend to be in areas with low shear, as estimated by sand deposition.