Shell volume (L m−2), prey density (ind. m−2), and index of ‘predator-free space’ (Sp/Pr) for each experiment by treatment type (n = 5).

Expt 1 used a fixed number of predator and prey individuals across treatments of variable levels of structural complexity. Expt 2 used the same structural treatments as the first experiment, but scaled the density of prey across treatments. Expt 3 used the same prey density treatments as the second experiment, but altered the amount of ‘predator-free space’ (by increasing interstitial space) in each structural treatment. Control treatments had no structure.