The worlds largest protected marine area has been an unexpected boon for migratory tuna, long the bellwether species for overfishing, according to new research published Thursday.

Researchers at the University of Hawaii analyzed data from fishing zones near the Papahnaumokukea Marine National Monument, a massive protected area near the state that has banned commercial activity for more than 15 years. While the marine protected area, or MPA, was mainly designated to protect local species that dont move around much, like coral and lobsters, the data suggests the zone has also helped tuna rebound, effectively serving as a fish nursery.

Catch rates of fast-growing yellowfin tuna increased 54% in waters near the protected zone after it was expanded dramatically in 2016. Catches of bigeye tuna, which grow more slowly, have rebounded 12% in that same period.

Its the first time research has shown a large, well-placed no-fishing zone can help migratory species like tuna which can travel hundreds or thousands of miles rebound and have a spillover effect in fisheries nearby. The report was published in the journal Science this week.

The research was funded by the National Oceanic and Atmospheric Administration and the National Science Foundation.