Temporal variation of abundance (ind m⁻², mean ± 1 SD) of macroinvertebrates collected in the control (white), one-crayfish (grey) and two-crayfish (black) enclosures. Only graphs for taxa displaying significant effects are depicted: (a) hydracarina, (b) leuctridae, (c) limnephilidae and (d) chironomidae. Crayfish density treatments that significantly differed from each other are denoted with different lowercase letters over the bars (a, b, c), and combinations of these letters (ab, abc) indicate a lack of effects in relation to individual groups.