Marine reserves: size and age do matter

TLDR

Marine reserves are widely used to prevent overfishing and conserve biodiversity, yet their optimal design remains uncertain and empirical evidence has not consistently linked reserve size to effectiveness. Analysis of 58 datasets from 19 European marine reserves shows that larger no‑take zones raise commercial fish density inside the reserve, buffer zone size has the opposite effect, and the benefits of protection grow with reserve age, underscoring the importance of reserve size and age in coastal spatial planning.

Abstract

Abstract Marine reserves are widely used throughout the world to prevent overfishing and conserve biodiversity, but uncertainties remain about their optimal design. The effects of marine reserves are heterogeneous. Despite theoretical findings, empirical studies have previously found no effect of size on the effectiveness of marine reserves in protecting commercial fish stocks. Using 58 datasets from 19 European marine reserves, we show that reserve size and age do matter: Increasing the size of the no‐take zone increases the density of commercial fishes within the reserve compared with outside; whereas the size of the buffer zone has the opposite effect. Moreover, positive effects of marine reserve on commercial fish species and species richness are linked to the time elapsed since the establishment of the protection scheme. The reserve size‐dependency of the response to protection has strong implications for the spatial management of coastal areas because marine reserves are used for spatial zoning.