In a swath of open ocean surrounding four volcanic islands off the west coast of Mexico, sharks and manta rays swim free. Humpback whales birth and raise their young. More than 300 species of fish, of which 36 are not found anywhere else in the wild, are sheltered from fishing. 

Known as the “Galápagos of Mexico,” the 57,000-square mile Revillagigedo National Park national park is the largest concentration of megafauna in the world—and North America’s largest marine protected area. 

Now, five years after the park was created, a new study has found that it has been good for wildlife—and Mexico’s fishing industry: the ban on fishing inside the reserve has not affected commercial fishing vessels’ ability to find and catch fish. The findings illustrate that a key ocean ecosystem can be successfully protected without economic sacrifice.

In other words, “we can have our fish and eat them too,” says ecologist Enric Sala, National Geographic Explorer in Residence and co-author of the study, published today in Science Advances. 

Tracking 2,000 fishing boats

Sala’s Pristine Seas initiative helped establish the reserve in late 2017. The reserve was opposed by those in the country’s commercial fishing industry, who argued that the marine protected area would significantly hamper their ability to catch fish. Sala says that the fishing industry opposition was unfounded in the first place: Mexico’s commercial fishing vessels only spent seven percent of their time fishing in the reserve’s waters before they were protected. Five years after the ban went into effect, Sala worked with a team of U.S. and Mexican researchers to see if anything had changed.

The team looked at two types of data: where boats were fishing, and what those boats caught, both before and after Revillagigedo was fully protected. The catch data, collected from the National Fisheries Institute of Mexico, revealed that for boats that historically fished within the reserve, and for boats that didn’t, catch volume didn’t change in the four years after the reserve was protected. 

The team also wanted to know if boats were actually fishing outside the reserve, and, if so, how their routes changed after the ban. Using satellite data pulled from the boats’ location trackers, the team used AI technology to detect where boats were fishing based on the speed and movements of the vessels (small or zig-zagging movements can indicate that a vessel is in the middle of fishing for tuna, for example). 

Data showed that fishing inside the reserve decreased by 82 percent after its waters were fully protected in 2017. It also showed that the overall area that vessels fished in decreased by 55 percent on average—protecting Revillagigedo didn’t result in vessels venturing further to catch fish.

The findings “add to a growing body of literature showing that fishing opportunities and ocean conservation need not be mutually exclusive—and can be mutually beneficial,” says Matthew Savoca, a postdoctoral research fellow at Hopkins Marine Station at Stanford University, who was not involved in the study.

Fishing wasn’t affected—why it matters

The argument that establishing marine protected areas has negative economic impacts on the fishing industry is a common—and effective—roadblock to establishing reserves. Currently, less than three percent of the global ocean is fully protected, a number that falls far short of the goal of the global community initiative to protect 30 percent of the ocean by 2030.

There is an “understandable fear” by governments that protecting swaths of ocean will harm fishing production, says Sala. But there is evidence that marine protected areas can actually boost the health of surrounding fisheries by offering refuge to large female fish—frequently targeted for catch—who produce the most eggs. 

“Big females are found only in no-take areas, so the number of babies they produce is so much greater than in areas where they are not protected,” says Sala. These offspring then help to replenish fisheries around the reserves, he adds.

Sala is hopeful that, moving forward, the same innovative AI technology can be used with satellite data to track fishing activity in and around other marine protected areas. 

“Before, people could claim many things about fishing,” he says, because there was such limited visibility into what vessels were doing. Now, “modern tools allow us to check claims by both the fishing industry and conservationists. It allows us to be more rigorous.”