New study shows spillover benefits from large marine protected areas

Increases in catch rates for fish such as tuna have been demonstrated near recently created Large-Scale Marine Protected Areas, including Revillagigedo, a group of islands in Mexico. This shows that Large-Scale Marine Protected Areas are large enough to protect highly migratory species such as tuna, especially bigeye tuna. Those are the findings of two research scientists, including an economics professor at the University of Hawaiʻi at Mānoa, who analyzed publicly available data with funding from the National Science Foundation. The findings were published in “Science” on Thursday.

“In 2004, there was only one Large-Scale MPA in the world, the Galápagos Marine Reserve in Ecuador. Today there are more than 20, including Papahānaumokuākea in the Northwest Hawaiian Islands. Most of these protected areas are in waters where tuna fisheries operate,” said lead author John Lynham, a professor in the Department of Economics at UH Mānoa’s College of Social Sciences. “This means that we can now test, for the first time, the impact of these marine protected areas, especially on tuna species like ʻahi and skipjack, which support a global industry worth over $40 billion.”

Understanding the interactions between Large-Scale Marine Protected Areas, tuna stocks and tuna fisheries is timely given international goals to protect 30% of the world’s ocean area by 2030 and the United Nations’ Biodiversity Beyond National Jurisdiction Agreement, an international treaty aimed at protecting biodiversity on the high seas.

Lynham and report co-author Juan Carlos Villaseñor-Derbez, a professor at the University of Miami’s Rosenstiel School of Marine, Atmospheric, and Earth Science, reviewed data from nine Large-Scale Marine Protected Areas across the Pacific and Indian oceans.

“We found that the spillover benefits, measured as the change in catch rates, are strongest just outside the boundaries of these MPAs and get stronger over time,” said Villaseñor-Derbez. “The effects were strongest for the MPAs that were heavily fished prior to protection and are now well-enforced.”

The research team claims to have found multiple examples from around the world of spillover benefits, resulting in an increase in catch rates outside of marine protected areas. On average, this spillover benefit resulted in a 12% to 18% increase in catch-per-unit-of-fishing-effort in the waters near protected areas.

Results across tuna species are relatively consistent, said the authors, with all species showing some evidence of positive spillover ranging from 2% to 11%, with the strongest benefits for bigeye tuna.

The research also finds that nations engaging in conservation reap the majority of the economic benefits. For example, close to 100% of the spillover benefits from the Revillagigedo protected area in Mexican waters flow to Mexican fishing vessels.

“While protected areas in Hawaiʻi were not the main focus of this paper, our research also reveals that the Papahānaumokuākea Marine National Monument, the world’s largest no-fishing zone, has caused a 10% increase in bigeye tuna (ʻahi) catch rates near the monument, in line with a recent finding of a 13% increase by researchers from the University of Washington and the Western Pacific Regional Fisheries Management Council,” said Lynham.

“A unique aspect of this research is that we built a global database on tuna catch using only publicly available data,” said Villaseñor-Derbez. “Anyone in the world can download the same dataset we used and replicate our analysis. That hasn’t been possible with previous studies on large-scale MPA impacts.”