Percentage cover of Pacific oysters (Crassostrea gigas) and densities of Parvulastra parvivipara sea stars underneath haphazardly selected boulders at two intertidal boulder-field sites (Cape Vivonne and Point Brown) on Western Eyre peninsula, South Australia. Percentage cover and boulder areas were measured by importing photographs (including a ruler for scale) of the underside of boulders into SketchUp v8 and using the programme to make the calculations.