Ocean Protection Around Hawaiian Islands Boosts Far-Flung ‘Ahi Populations

Native Hawaiians cherish the thin strand of atolls stretching 1,000 miles northwest from the archipelago’s largest islands—Hawai’i, Oahu and Maui—toward Midway Atoll as central to their creation beliefs and representative of the Hawaiian concept of kinship between humans and the natural world. 

Research published Thursday in the journal Science shows that protections of the area first initiated by kūpuna—esteemed Hawaiian elders—have benefited migrating fish and people who depend on them far from the islands.

The remote area includes just a few tiny bits of coral-ringed land with endemic plants and birds, islets that seem to float above a vast aquamarine seascape of submerged reefs, volcanoes and canyons that shelter abundant populations of corals, fish, turtles and seals. Parts of it have been protected since the early 1900s, when President Theodore Roosevelt outlawed bird hunting on some of the islets. 

In 2006, President George W. Bush designated a national marine monument, and in 2016, President Barack Obama expanded it to 580,000 square miles, an area nearly the size of Alaska. Today, Papahānaumokuākea Marine National Monument is one of the largest single protected areas on the planet.

The research in Science shows that fishing restrictions in the vast monument are helping to restore populations of ‘ahi (tuna) and other large fish that use the area as a marine nursery. While the benefits of no-fishing zones for sedentary marine life like corals or lobsters are well documented, conservation scientists weren’t sure that any protected area is large enough to help species like ‘ahi that migrate far from the protected areas.

The study found that, since the monument was enlarged in 2016, fishers are catching more ‘ahi hundreds of miles away from its boundary. The catch rate in waters near the protected zone increased 54 percent for yellowfin tuna, 12 percent for bigeye tuna and 8 percent for all fish species, showing that fish populations are increasing in and around the protected zone. The researchers focused on those two species of ‘ahi because of their cultural importance to Native Hawaiians, their roles as apex predators that shape ecosystems and for their global importance as a fishery valued at $40 billion per year that employs millions of people.

Ancient Fishing Practices and Sacred Rituals Underpin Conservation

Native Hawaiians have been fishing for tuna in the area since the Polynesians arrived on the Hawaiian Islands, said co-author Jennifer Raynor, a professor in the department of forest and wildlife ecology at the University of Wisconsin-Madison. 

“Culturally, this is one reason why tunas are so important to the native Hawaiians,” she said. “There’s this really long significance, both for diet and other cultural practices.” The new research suggests that some tuna don’t travel as far from home as once thought. The marine sanctuary is a nursery for juvenile yellowfin, and it turns out that many of the fish stay in the region. 

Tracking what they called the “spillover benefits” to regions farther from the protected area wasn’t easy, she said.

“We think there are two special ingredients why this monument seems to have been beneficial for these large species,” she said. “One is its size. This is the largest no-fishing zone on the planet. It’s almost four times the size of California. So this provides way more protection than the smaller protections that we’ve seen in the past.”

The monument’s placement and shape also contribute to the spillover benefits, she said. 

“It was put in a place where yellowfin tuna have larval nurseries,” she said. “It wasn’t why they placed it there, but it turned out that it was a really good choice.”

Those same geographical features may buffer the species that depend on the protected area from global warming impacts as well, she added. The monument covers much of the tunas’ comfort zone, “with latitudinal coverage over their preferred temperatures,” which means the fish can move from warming waters to more hospitable areas without leaving the no-fishing zone, she said.

Co-author Sarah Medoff, a fisheries economist at the University of Hawaiʻi at Mānoa,

said she started studying the commercial tuna fishery for big eye tuna, because of their huge value in Hawaii. 

“They’re arguably the most profitable fishery that we have,” she said.

Originally, Medoff said, the researchers were just looking to show the spillover benefit the migrating fish provided to areas outside the protected zone.

“We took about 10 or 20 different species, ran them through our models, and when we estimated this positive effect for yellowfin and bigeye tuna, we were all really shocked,” she said. “But then we said, ‘Wait a second. Let’s make sure we’re accounting for everything.’”

To make sure that the increased catch was not due to something other than the influence of the no-fishing zones, like changes in general overall ocean conditions, they used models that separate the effects of natural changes from the effect of the expanded marine monument. 

“We constructed a series of tests to disprove these results, to try to figure out if we could find any other explanation that would potentially be driving these results other than the expansion of the marine protected area,” she said. “Every single time we ran an analysis, it just furthered our confidence in our results.”

A New Co-management Model Evolves

Papahānaumokuākea sets a good example for co-management of important biocultural resources, with local long-term knowledge as part of the foundation, said Kekuewa Kikiloi, an associate professor at the Hawai’inuiākea School of Hawaiian Knowledge that was recently established at the University of Hawaiʻi at Mānoa campus. 

Kikiloi, who was not an author of the new study,  said the research is important in the context of global policy discussions about the need to protect and restore large areas of both ocean and land ecosystems to prevent biodiversity collapse and to bolster their ability to remove carbon dioxide from the atmosphere. Such large-scale collaborative management will be needed at the international level to meet global goals for preserving nature. The marine monument has already felt the impacts of climate change, for example with coral bleaching and damage along even some of the most remote reefs, according to a 2020 report.

“This idea of large scale marine protected areas is relatively new,” he said. “That has lended a kind of urgency of learning that has spread throughout the Pacific,” leading to the formation of an alliance of marine protected areas. “These different nations communicate a lot, collaborate a lot and share data and best practices. It’s pretty amazing to see the level of mutual support and how much this genre of marine conservation is growing so quickly.”

As global warming makes massive ocean die-offs a grim reality, the new study and other research suggest that Papahānaumokuākea could be one of the most important marine protected areas “because of its position in the upper part of the Northern Hemisphere,” he said. Scientists have noted that the waters in the protected area are much colder than in marine preserves farther south, potentially making it “like a Noah’s Ark” for ocean species threatened by warming.

“I do think that these large marine protected areas are going to provide a sense of stability in the ocean in a time when there’s so much change, with global warming in particular,” he said.

At Papahānaumokuākea, the collaborative approach evolved over decades and was formalized in 2006 when the Office of Hawaiian Affairs was made a co-trustee, along with the Department of Commerce, the Department of the Interior and the State of Hawai’i. 

“It is highlighted as sort of a model, at least for this region,” Kikiloi  said. “It’s a little bit of a more unique situation because it’s so remote.” The fact that the monument didn’t abut people’s backyards, as it might have in the main Hawaiian Islands, left few stakeholders to argue over its management, he said.

“But in the beginning, like in many other places, there was confrontation between Indigenous people and colonizers,” he said. “It was sort of a top-down thing, where the agencies would tell us what they were going to do. But over time, a lot of trust was built. We’ve gone on adventures and trips up into this pristine wilderness together. We’ve learned to survive and live together on boats and in camps. I think all of those experiences started to bring us together in a way that built goodwill between the Indigenous peoples and the management agencies.”

Every new level of protection inserted more language into the management policies that recognized the importance of Indigenous culture, collaborative work and meaningful consultation, Kikiloi said.

“It really solidified in 2016, when we pushed for the expansion of the monument and President Obama elevated the Office of Hawaiian Affairs to the level of co-manager, he said.”

Trust Helps Build Conservation Successes

Kikiloi has worked on developing the Native Hawaiian component of the management plan for the monument, which is now being considered as a model for overall management. And the collaborative efforts have been “called out by President Biden as an example of traditional ecological knowledge being really truly incorporated … with representation on a community advisory council and designated seats for Native Hawaiians and elders,” Kikiloi said.  

“We just keep sort of integrating and blurring the lines,” he said. “We’re all working together and it’s really a great situation, built on trust, built on relationships, which is kind of a cornerstone of the culture of Hawaii.”

Research showed that Native elders had historic connections to the protected area associated with subsistence fishing and spiritual practices, but during the last few decades, concerns grew about depletions of the area by industrial fishing operations, adding urgency to the push for protections.

“Really, it’s the only abundant area left in Hawaii,” he said. “Around the main Hawaiian Islands, I would say the fisheries are on the verge of collapse, If not already collapsed.”

Big ‘ahi have likely been an important local food source ever since people came to the islands because there weren’t really many land mammals to hunt for food, he said. 

“Most of the meat, most of the protein was coming from the ocean and in particular, pelagic species that were seen as major league trophy hunting in a way,” he said. “And it was associated with magic. It required a party of people, some to row the canoe, others to tow the trolling line and reel in the fish.”

`Ahi are strong and exceptionally fast swimmers that can weigh several hundred pounds, “so to land one of those fish was a major accomplishment, and it fed entire villages,” he said.

In the distant reefs of what is now the marine monument, fishers didn’t catch more than they needed, he said. “There was more of an emphasis on the sacred and the rituals, so that it effectively functioned like a marine protected area.”

Good Neighbors, Good Conservation Policy

Co-author Medoff said that ‘ahi was part of the cuisine at every function and family gathering as she grew up in the islands. 

“Whether it’s a Halloween party, or a graduation, a wedding, funeral potlucks or barbecues at the beach, it is the focal point of the dinner table,” she said. “It wasn’t a question of who is bringing the poke or the sashimi, it was more like, how many different ones do we have on the table? That’s what everybody kind of gravitates to first whenever they start eating.”

The research project “got me really thinking about what this species means to me personally,” she said. “It’s a lot more special to receive a cut of tuna from my neighbor who just caught it the day before or earlier that day, rather than buying it from the store. It brings people together and creates community. And that, I think, is really important to the culture of Hawaii, because we really pride ourselves on focusing around family and friends, and being good neighbors to each other.”

She said the findings of the study provide a way of thinking about the global ocean conservation efforts needed to meet policy goals and international conservation agreement targets.

“We do share the same resource and use the ocean multilaterally,” she said. “And so I think the only way that we’re really going to start achieving broader conservation goals is to start working with each other a little bit more.”