Study: The ‘ripple effect’ of marine protected areas benefits fish and fisheries | New

Scientists have shown for the first time that protecting highly valuable but endangered tuna in huge marine reserves pays off in the recovery of so many migrating fish that catch rates for some species have increased by 54 % near a Hawaiian reservation where fishing had been prohibited.

This is due to what is known as the “ripple effect”, when protected tuna populations grow so healthily that they expand beyond a marine protected area. These reserves must, however, be carefully designed and adapted to the biology of the protected species, according to the researchers.

Scientists have already proven that marine protected areas that prohibit fishing benefit populations of corals, lobsters and other critters that travel little and are more easily studied. But whether those reserves helped tuna, which can migrate thousands of miles from their spawning grounds, was an open question.

The findings of the peer-reviewed study published Thursday in the journal Science have important implications, as rising ocean temperatures due to climate change are expected to alter tuna migration and complicate fish protection efforts. It comes amid a push to make large swaths of the ocean off-limits to industrial fishing, even as some Pacific island nations shrink or abandon huge marine sanctuaries they established to protect tuna after the decline in fishing income.

“Tuna is a $40 billion global industry and a single tuna can be worth a lot of money, said Jennifer Raynor, co-author of the paper and assistant professor of natural resource economics at the University of Wisconsin-Madison. “Nations have significant up-front costs when establishing a marine protected area and need to know that they will gain benefits later to compensate for lost fishing revenue.”

In 2019, a single 613-pound bluefin tuna sold for $3.1 million in Tokyo, a record price equivalent to around $5,000 a pound. Tuna, however, are also critical to ocean health as the top predator that regulates marine ecosystems. Some species are over 10 feet long, weigh 2,000 pounds, and cross the ocean at over 40 miles per hour.

Raynor and his colleagues set out to study the impact on tuna of the world’s largest fully protected marine reserve, the 583,000 square mile Papahānaumokuākea Marine National Monument in the Northwestern Islands. from Hawaii. President George W. Bush established the reserve in 2006 and President Barack Obama quadrupled its size in 2016.

The researchers analyzed catch data collected by the National Oceanic and Atmospheric Administration (NOAA) between 2010 and 2019. The information was collected by observers stationed on commercial tuna boats operating within 345 miles of the monument. As observers are on board only 20% of the vessels, the scientists also looked at tuna catch data recorded in the captains’ logbooks.

“We are extremely fortunate in this case that NOAA is collecting very high quality data on what is being captured and where exactly it is being captured,” said John Lynham, study co-author and professor of economics at the University. University of Hawaii. .

The researchers determined that overall yellowfin tuna catch rates – defined as the number of tuna caught per 1,000 hooks deployed – increased by 54% within 345 miles of the Papahānaumokuākea Marine National Monument. Bigeye tuna catch rates jumped 12% and catch rates for all species jumped 8%.

“I think the wider implication is that if we can make protected areas big enough, they can protect migratory species,” Raynor said. “I think that’s something that was doubted for a long time.”

There is a catch, however. The shape of a marine reserve should be designed to maximize the protection of species based on their life cycle and migratory patterns. “You don’t necessarily want to just draw a big circle around an area,” Lynham said.

The Hawaii National Monument was not created to specifically preserve tuna, but to protect endangered monk seals and other marine life, as well as cultural sites. Raynor said its rectangular shape could be a “lucky accident” because its 1,350-mile length runs east to west, which is the direction tuna prefer to travel.

Lynham called climate change a wild card when designing large marine protected areas. “The consensus view right now is that most tuna species will move away from the equator and head towards the poles,” he said. “In the case of Papahānaumokuākea, this means tuna will likely move in and out of the current protected area boundaries.”

The Pacific island nation of Palau banned tuna fishing in 80% of its exclusive economic zone in January 2020 when it established the 183,428 square mile (475,077 km2) Palau National Marine Sanctuary. However, a decline in commercial fishing revenue from foreign fleets prompted the government to begin a planning process to redesign and reduce the size of the sanctuary.

King Sam, director of the Palau National Marine Sanctuary, said the lack of data on tuna and other species in Palau’s waters has proven to be a challenge for the management of the marine reserve.

“Any lessons we can learn from studies in Hawaii and other places that have established large-scale marine protected areas would really help inform how we do it,” he said.

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