Fig 2 -

Mean (+1SE) densities (left) and shell lengths (right) in 1970 and 2017, for (A, B) Cymbula granatina, (C, D) Scutellastra argenvillei and (E, F) S. granularis. No historical length-data were available for S. argenvillei and it was absent from Wireless Point. Shell length data for were available for only one site (Wireless Island). Asterisks between years and different letters above error bars indicate significant differences (P < 0.05).</p

Results of two-way nested ANOVAs of the densities of <i>C</i>. <i>granatina</i>, <i>S</i>. <i>argenvillei</i> and <i>S</i>. <i>granularis</i> with factors protection level and site (nested in protection level).

Results of two-way nested ANOVAs of the densities of C. granatina, S. argenvillei and S. granularis with factors protection level and site (nested in protection level).</p

Multivariate generalized linear model analysis of the community composition to test for differences between years and among intertidal zones, and their interaction.

Multivariate generalized linear model analysis of the community composition to test for differences between years and among intertidal zones, and their interaction.</p

Fig 4 -

Mean (+1SE) densities (A, C) and sizes (B, D) of Scutellastra granularis in different intertidal zones at Wireless Island before the arrival of Mytilus galloprovincialis in 1970 (A, B) and after it has invaded in 2017 (C, D). Lower-case letters show Tukey HSD results with different letters indicating significant differences (P < 0.05).</p

Two-way ANOVAs of the densities of <i>C</i>. <i>granatina</i> and <i>S</i>. <i>granularis</i> comparing temporal differences with factors site and time, and their interaction.

Two-way ANOVAs of the densities of C. granatina and S. granularis comparing temporal differences with factors site and time, and their interaction.</p

Map of the Table Mountain MPA showing the study sites (red circles).

Wireless Island, Wireless Point and Kommetjie are in a ‘controlled’ zone where harvesting is permissible, and Scarborough North and South in a ‘restricted’ no-take zone.</p

Fig 6 -

Multidimensional scaling (MDS) of species abundance in the four zones: (A) low shore, (B) mid shore, (C) high shore and (D) top shore, reflecting differences in community composition among harvested (Kommetjie, Wireless Point) and no-take areas (Scarborough North, Scarborough South). Abundances of diagnostic species are presented in multi-dimensional space as well as vectors based on correlations.</p

S1 Fig -

Sampling design for (A) temporal comparison at Wireless Island and Wireless Point (Before-After component, 1970 vs. 2017) and (B) spatial comparisons of four sites (Control-Impact component of sites in 2017). MHWS = mean high water springs and MLWS = mean low water springs. Squares indicate quadrats. (TIF)</p

Results of two-way nested ANOVAs of the sizes (shell lengths) of <i>C</i>. <i>granatina</i>, <i>S</i>. <i>argenvillei</i> and <i>S</i>. <i>granularis</i> with factors protection level and site nested in protection level.

Results of two-way nested ANOVAs of the sizes (shell lengths) of C. granatina, S. argenvillei and S. granularis with factors protection level and site nested in protection level.</p

Univariate tests for differences in abundance over time and among intertidal zones.

P-values are adjusted for multiple testing using a step-down resampling algorithm (Wang et al. 2012). Goodness-of-fit of the models is indicated by the residual deviance (Dev), with lower values indicating better fit. Changes in the abundance over time are shown as increases (+), decreases (-) or no change (0). Blank cells = absence or scarcity that prevented analysis. (DOCX)</p