Marine reserve networks conserve biodiversity by stabilizing communities and maintaining food web structure

Abstract

Theory predicts that networks of fully protected marine reserves conserve biodiversity by stabilizing communities and maintaining food web structure in the face of inadequately constrained fishery exploitation. To test these ideas we examine trends in species incidence, community and trophic structure of temperate reef fishes over an eight year period within the Fiordland no‐take marine reserve network, at management zones subject to commercial fishing and at those closed to commercial exploitation but open to recreational fishers. We use information from extensive stratified subtidal surveys of the reef fish community and abundance of macroalgae, as well as oceanographic data collected in 2002, 2006 and 2010. Our analyses indicate a regional decline in species richness of exploited reef fish in areas open to fishing between 2002 and 2010. Following implementation of spatial management (2006–2010), richness of ‘exploited' species increased within marine reserves, but remained unchanged in areas open to fishing. Further, analysis of differences in community structure in this time period (2006–2010) indicate that both ‘exploited' and ‘non‐target' groups were more stable within marine reserves than were those within fished areas. Consequentially average trophic level of the community remained stable within marine reserves but declined sharply in areas open to fishing, indicating both declines in large omnivorous species and increases in forage fish within exploited regions. These analyses offer an important test of the direct and indirect effects of marine reserve networks on the dynamics of reef fish communities at the landscape scale. We demonstrate the potential for multiple no‐take reserves spread over a heterogeneous marine landscape to maintain biodiversity by stabilizing community structure and preserving intact food webs on a regional scale.