Marine protected areas are linked to higher predation rates by fish in shallow urbanised reefs, but only in no-take reserves

Abstract

Marine protected areas (MPAs) in which fishing is limited are a widespread management strategy to protect marine ecosystems. While many studies show clear effects of MPAs on fish biomass, much less is known about how protection influences the strength of ecological processes such as herbivory and predation. We characterised fish assemblages and used feeding assays to contrast rates of herbivory and predation by fish in MPAs (no-take and those with partial protection) and in fished sites in Sydney, Australia’s largest city. In no-take MPAs, large fish were more abundant, species richness was greater, and the biomass of predatory, herbivorous and all fish combined was higher. In contrast, sites with partial protection were indistinguishable from fished sites. Predation was higher in no-take MPAs than in partially protected MPAs, while herbivory was less influenced by protection status. These results show that protection from fishing within urbanised reefs can facilitate energy flow to higher trophic levels via increases in predation.