Could an ancient Hawaiian marine technology help depleted ocean ecosystems recover?

It’s early morning and Dr. Kapono Ciotti is addressing a group of about 30 children who are gathered on the grassy bank of a pond. Behind them, jagged volcanic peaks rear skyward, while on the other side the Pacific Ocean stretches to the horizon, separated from the pond by a shallow sea wall. This is Waikalua Loko Iʻa, an ancient aquaculture facility on Oʻahu, Hawaiʻi’s most populous island. “We humans are the younger siblings of ʻāina, of nature,” Ciotti tells the kids. “So, when we work today in the pond and on the wall, I want you to think about the fact that we have a reciprocal responsibility. What we do for ʻāina, ʻāina does back for us.”

If there is one word that captures the spirit of the Hawaiian Islands it is elemental. The confluence of massive Pacific swells and colossal volcanic peaks, some still spewing fire, make for an exhilarating experience. And yet, here in the fertile hinterland between ridge and reef, Hawaiians have a millennia-old history of cultivating both terrestrial and aquatic ecosystems, employing sustainable technologies as part of a traditional system of land division known as ahupuaʻa that extends all the way from upland to sea.

Fundamental to this system are rich repositories of seafood and other marine resources that actually feed the ocean instead of depleting it. They are called loko iʻa —literally ‘fishponds’—and they are making a comeback.

Dr. Kapono Ciotti is the CEO of Pacific American Foundation, a local non-profit and partner of Hawaiʻi Blue Schools Hui—a regional group of the Blue Schools Global Network, coordinated by UNESCO—which integrates ocean education into school curricula.

The Hawaiʻi Blue Schools Hui aims to strengthen students’ ocean literacy through place-based action projects that celebrate Hawaiʻi’s unique biodiversity and rich cultural legacy. This learning path was made possible by SEA BEYOND, the project by Prada Group conducted in partnership with the Intergovernmental Oceanographic Commission (IOC) of UNESCO.

“The kuapā [fishpond wall] is porous, so it allows seawater in and the mākāhā [sluice gate] is a technology that Hawaiians were able to create that allows small herbivorous fish to enter the pond while keeping the predators out,” says Ciotti, gesturing across the enclosed body of water. “This is one of what used to be 50 ancient Hawaiian fishponds here in Kāneʻohe Bay, that fed our people for generations.”

Loko iʻa work by mixing freshwater with seawater to create a brackish, nutrient-rich broth that supports high concentrations of seaweed, limu, that is an ideal food source for herbivorous fish. The fish can grow large in the safety of the loko iʻa, but because juveniles are able to move freely between the pond and the open ocean, they still provide a food source for marine predators.

“It creates a balance between the local and nearshore environment. So, we can really help sustain and even bring back health to the ocean environment,” says Ciotti.

By comparison, commercial aquaculture, with its rapid growth cycles and preference for high-value protein-craving carnivores, like tuna and salmon, extracts enormous amounts of biomass from the ocean. An estimated 20 million tons of small fish species like sardines, herring, and anchoveta (20% of all wild-caught fish) were extracted in 2025 to be used as fishmeal in high-value aquaculture production. Then there is the added issue of pollution, where everything from antibiotics to pesticides to fish feces are flushed into surrounding waters.

Loko iʻa, however, provided a primary food source that was genuinely sustainable, actively filtering water so that it benefited the overall ecosystem. Streams would pass through wetland agroecology picking up nutrients, which fed plankton in the ponds, before flowing into the ocean. “Back in the day, Hawaiʻi had somewhere between half a million and a million people, and all of the protein that we needed, the vast majority, was farmed in these ponds,” says Ciotti.

When Europeans first made contact with the Hawaiian archipelago in 1778, there were close to 500 functioning ponds producing an estimated 2 million pounds of fish each year. By 1994, only six were still operating. The good news is that today there is a major effort underway to restore Hawaiʻi’s loko iʻa. Communities are rebuilding sea walls using traditional dry stack methods, replacing invasive mangroves with native species and reintroducing herbivorous fish to the ponds. Says Ciotti, “Because there are so few left, it is super important that we get kids out onto ʻāina, onto the land, learning with hands-on education.”

But can legislators and the aquaculture industry at large learn from the loko iʻa model? The evidence is promising. In January 2026, the State of Hawaiʻi implemented the Restorative Aquaculture Development Program, which officially prioritizes loko iʻa and other native systems over commercial operations. Elsewhere, a number of regenerative start-ups like GreenWave in the United States, and the Seaweed in Ecosystem Enhancing Aquaculture for Growth and Sustainability (SEAGROW) initiative in the EU are looking to scale so-called polyculture farming systems founded on the same nature-positive principles as Hawaiʻi’s loko iʻa.

“We’re really proud to be a partner with Blue Schools and to be able to bring kids out onto site so we can inspire them through hands-on learning,” says Ciotti, as the kids remove invasive seaweed from the pond, squealing happily as they squish around in the mud. “We find if we get kids to work in the loko iʻa, they become even better ocean stewards.”

The activities of the Hawaiʻi Blue Schools Hui are showcased in the second documentary of the 2026 series, created by National Geographic CreativeWorks, Prada’s storytelling partner, starring actor Letitia Wright and Titouan Bernicot, National Geographic Explorer and SEA BEYONDer Goodwill Ambassador of the project, and founder of Coral Gardeners—the non-profit organization dedicated to restoring coral reefs.