Establishing protected areas in the sea helps not only the animal species that live there, but also those in the surrounding area, including migratory species such as tuna. This is what US researchers report after investigations in the world’s largest marine reserve around Hawaii in the journal Science. Both the environment and the fisheries benefited from the positive effects: populations weakened by fishing can recover undisturbed in the protected areas and thus ensure higher catch rates in nearby regions.
Some countries around the world, such as the USA, have committed to protecting 30 percent of their marine areas by 2030. In order to achieve this goal, new protected areas must be established, among other things. In such zones, activities such as fishing or mining are strictly controlled or prohibited.
However, what is beneficial for sea creatures could mean a loss for the fishing industry. After all, she loses such important fishing grounds. However, fish stocks can apparently increase within protected zones to such an extent that this compensates for the loss of fishing grounds. In order to test such an effect, the team led by Sarah Medoff from the University of Hawaii in Honolulu examined the Papahānaumokuākea marine reserve in northwestern Hawaii.
What began in 1909 as a small sanctuary for nesting seabird colonies became nearly 100 years later, in 2006, the largest marine sanctuary within US waters. In 2016, the protection zone around the northwestern islands was expanded again. At over 1.5 million square kilometers – almost four times the size of California – Papahānaumokuākea Marine National Monument is the largest contiguous protected area in the world.
In order to determine the consequences for fisheries, the researchers examined how the fishing quotas changed after the extension of the protected area and whether this effect was greater near the protected area than further away. To do this, they evaluated data on fish species caught, fishing locations, ship characteristics and the fishing gear used since 2010.
In fact, they tended to find higher catches, particularly for yellowfin tuna (Thunnus albacares) and bigeye tuna (Thunnus obesus). Their analysis thus suggests that populations of migratory species can also recover in marine protection zones. “For the first time, we can show that a no-fishing zone provides a sanctuary for migratory fish species while also having a positive spillover effect on fisheries,” said co-author John Lynham in a University of Hawaii press release.
According to the report, the catch rate increased by 54 percent for yellowfin tuna and 12 percent for bigeye tuna after the expansion of the protected area in the nearby waters. For all fish species combined, catch rates in the regions around Papahānaumokuākea increased by 8 percent.
According to the researchers, these positive consequences for fisheries are probably due to the enormous size of the no-fishing zone in combination with the return behavior of some tuna species. “Over the past 30 years, we’ve learned that tuna don’t stray as far from home as we once thought,” said co-author Jennifer Raynor of the University of Wisconsin at Madison. “The Hawaiian Islands are a nursery for yellowfin tuna. It has also been found that many of these fish species remain in the region and do not migrate.”
Medoff and her colleagues’ findings underscore the value of large-scale marine protected areas, says Kekuewa Kikiloi of the University of Hawaii, who was not involved in the study. The protections that were fought for by the Hawaiian natives and other interest groups for Papahānaumokuākea would benefit everyone: nature, the Hawaiian people and also the fisheries.
