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Scientists see clearly that marine protected areas protect fish, and fishers, alike.


Scientists see clearly that marine protected areas protect fish, and fishers, alike.

Mexico’s industrial fishers claimed that banning them from a marine reserve would decrease their catch by 20%. A multinational team of researchers tested that assumption.
June 16, 2023

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Researchers have provided the first evidence that the largest fully protected marine reserve in North America doesn’t exact a cost on fisheries. By looking at Revillagigedo National Park, the world’s 13th-biggest MPA, they showed that industrial fish catch in the region was unaffected by the reserve’s closure in 2017. Not only that, but closing the area to fisheries didn’t drive vessels to deplete stocks elsewhere.

The key takeaway? “Conservation is not a threat to fisheries,” says Fabio Favoretto, a numerical ecologist at University of California San Diego, and co-author on the study. “Conversely, working together to improve marine conservation is fundamental. Fishing benefits from MPAs.”

The multinational study was launched partly in response to opposition from Mexico’s industrial fishing fleets, who claimed that banning fishers from the 147,000 square kilometer marine reserve, which lies just off the coast of Baja California, would drive down their catch by 20%. The team of multinational researchers on the new Science Advances study were able to test this assumption by comparing fishing activity before and after the MPA was set up. 

To do this they relied on open-access satellite data beamed out by the vessel monitoring systems of 2,000 individual fishing boats. That was combined with machine learning techniques to track and map fishing patterns across the region, covering the period between 2008 to 2022—which incorporated the five years after the MPA was set up. Then they paired this information with government data on the catch landings from industrial fleets to get a read on how these might be affected by the off-limits reserve.


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The first big reveal was that the MPA had been effective in keeping fishers out: a small minority of vessels broke the law and continued fishing in the closed zone, which was visible in the satellite tracking data. But fishing activity declined by 82% on average after the MPA was closed off, suggesting that conservation laws can be effective and are respected at sea.

As for catch, the researchers found that after the reserve had been established, there was no statistically significant change in the amount of fish that vessels, who had historically fished in the area, managed to scoop up. The same was also true for vessels that had never fished in the MPA: its closure made no difference to the quantities of catch they landed at the dock. 

One fear associated with marine closures is that they may simply displace fishing activity to other regions—and yet, this study proves that even that wasn’t the case. In fact, the vessels that used to fish in the MPA reduced their fishing area by 53% on average after the MPA was set up. Rather than scoping out new territories to fish, this suggests their fishing activities became more geographically constrained—yet didn’t affect the amount they were able to catch. 

A possible explanation for how more catch could be possible from a smaller area is that protected areas may increase fish availability at the legally fishable reserve edge—something known as the ‘spillover effect’. Whether that’s what is hapenning here is tricky to say, Favoretto says. “We haven’t tested that directly because data are not fit for that purpose.”

He holds out hope for the conservation impact of the closure, however. “We have evidence from other studies, as well as unpublished data we hope to publish soon, that the marine communities in Revillagigedo are thriving, compared to other areas which have been overfished.” 

Despite these encouraging findings, the authors do caution that exclusive conservation zones may not be a silver bullet and won’t necessarily be the best fit for every marine scenario—for instance in places where artisanal fishers need access to the fish that are their livelihoods. Unlike industrial fleets, their small size makes them more dependent on specific fishing zones. 

Either way, this research is one compelling piece of evidence proving the benefits of conserving the ocean, just 3% of which is fully-protected, according to the study. As the research shows, its benefits can extend to fishers—and perhaps in more ways than one. 

“I hope that the…critical importance of transparent data is underlined even more by our results, which work both ways,” Favoretto says. “Before our study many were (informally) accusing the fishing industry [of] operating illegally in the Revillagigedo area, which we now know is not true.”

Favoretto et. al. “The largest fully protected marine area in North America does not harm industrial fishing.” Science Advances. 2023.

Image: iStock/piola666

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