Large Recovery of Fish Biomass in a No-Take Marine Reserve

Octavio Aburto-Oropeza,Enric Sala,Grantly R Galland,Exequiel Ezcurra,Ismael Mascareñas-Osorio,Brad Erisman,Howard Browman

doi:10.1371/journal.pone.0023601

Abstract

No-take marine reserves are effective management tools used to restore fish biomass and community structure in areas depleted by overfishing. Cabo Pulmo National Park (CPNP) was created in 1995 and is the only well enforced no-take area in the Gulf of California, Mexico, mostly because of widespread support from the local community. In 1999, four years after the establishment of the reserve, there were no significant differences in fish biomass between CPNP (0.75 t ha−1 on average) and other marine protected areas or open access areas in the Gulf of California. By 2009, total fish biomass at CPNP had increased to 4.24 t ha−1 (absolute biomass increase of 3.49 t ha−1, or 463%), and the biomass of top predators and carnivores increased by 11 and 4 times, respectively. However, fish biomass did not change significantly in other marine protected areas or open access areas over the same time period. The absolute increase in fish biomass at CPNP within a decade is the largest measured in a marine reserve worldwide, and it is likely due to a combination of social (strong community leadership, social cohesion, effective enforcement) and ecological factors. The recovery of fish biomass inside CPNP has resulted in significant economic benefits, indicating that community-managed marine reserves are a viable solution to unsustainable coastal development and fisheries collapse in the Gulf of California and elsewhere.

Highlights

Overfishing has impacted marine biodiversity and ecosystems both directly and indirectly throughout history [1,2]
Evidence supporting the positive effects of no-take reserves include a greater abundance and biomass of fish inside marine reserves than in fished areas [see meta-analysis in 4]; an exponential increase of predatory fish biomass [e.g., 5,6]; and shifts in species composition and trophic cascades that result in the restoration of natural marine communities within protected areas [7,8,9,10]
Change in fish biomass for each trophic group was higher at Cabo Pulmo National Park (CPNP) than at other core zones or in open access areas

Summary

Introduction

Overfishing has impacted marine biodiversity and ecosystems both directly (through removal of significant biomass) and indirectly (by changing ecological linkages) throughout history [1,2]. Evidence supporting the positive effects of no-take reserves include a greater abundance and biomass of fish inside marine reserves than in fished areas [see meta-analysis in 4]; an exponential increase of predatory fish biomass [e.g., 5,6]; and shifts in species composition and trophic cascades that result in the restoration of natural marine communities within protected areas [7,8,9,10] While these ecological changes operate on decadal times scales through a series of transient states [5,11,12], initial detections of both direct effects of area closures on target species and indirect effects on other taxa through cascading trophic interactions can be observed much sooner (5 and 13 years, respectively) [13,14]. The long-term success of marine reserves is a social issue that requires strong local leadership, social cohesion, involvement and effective self-enforcement within the community, and inter-generational coordination [20,21]

Methods

Results

Conclusion