At both exposed shores, six well drained 2=2 m plots, at least 10 m apart, were
selected at mid-tide level (Port St. Mary, 2.7–4.0 m above LAT; Derbyhaven, 2.65–3.9
m above LAT). Areas with a high density of barnacles andror fucoids were avoided. At
both sheltered shores, six patches of limpets of between 0.2 and 1.25 m2 in area were
selected beneath the dense Ascophyllum canopy at mid-tide level Žinner Langness
3.0–4.2 m above LAT; outer Langness 2.8–4 m above LAT.. The density and length
frequency of limpets at all selected plots and patches were determined. Density was
higher in the sheltered shore patches, and thus, the limpet population in each patch could
be manipulated to closely resemble the density and length frequency of the exposed
shore limpet population.