Evidence of rebound effect in New Zealand MPAs: Unintended consequences of spatial management measures

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Marine ecosystems worldwide are under threat from overfishing, and marine protected areas (MPAs) have been shown to be an effective management tool that result in greater biodiversity, spawning stock, fish size and overall biomass within their boundaries. However, little is known about the impact of commercial fishing immediately outside MPAs. Using commercial fishing data compiled by New Zealand’s Ministry for Primary Industries, we used regression discontinuity methods to investigate how bottom trawling activity changed before and after the implementation of several types of offshore MPAs within New Zealand’s exclusive economic zone.

Despite reductions of fishable area in all five MPA systems we studied, total biomass extraction tended to discontinuously increase following the designation of a site to be an MPA. Examining trends in catch per unit effort, total trawl area and the number of fishing events, there was little evidence that these immediate increases in catch were associated with spillover or recruitment effects from within the MPA boundaries. Rather, these observed jumps appear to be due to changes in commercial fishing behaviours.