In Atlantic Canada, rockweed plants vary regionally resulting in distinct canopy structures. In this study, we used large-scale field surveys and multivariate statistics to demonstrate that the observed differences in canopy structure are further linked to distinct communities of associated species. Importantly, measures of plant and canopy structure (e.g. length, circumference, density) were much better predictors of associated community structure than rockweed biomass, which is often used for single-species monitoring. Thus, information about canopy structure and associated species composition should be incorporated into region-specific ecosystem-based management of the rockweed harvest.