Perumytilus purpuratus mean survival in competition with P. praeputialis. Inverted filled triangles, mussel survival, overgrown by tunicate, at the M-LIF (treatment 1). Open circles, mussel survival, no overgrown by tunicate, at the M-LIF (treatment 2). Filled circles, mussel survival at the M-UIF (treatment 3, control). Error bars are confidence limits at 95%. The right Y axis (filled square) shows the proportion (mean ± 1 SE) of mussels overgrown by P. praeputialis in treatment 1.