When the trucks pulled up to the 55-acre pond, Walter Ritte, a 70-something, whisper-quiet firebrand, climbed out, along with a group of fishpond restoration activists. They unloaded 10 insulated boxes containing bags of squirming fingerlings, known as pua, and walked through a tunnel cut into the mangroves along the top of the wall, a parade of children and dogs trotting in their wake. Two men hopped into the pond, water rising to mid-thigh. They placed the bags in the water to acclimate the pua, monitored them for a time, then released the fish. The 3,500 or so fingerlings huddled together in the shallows, their gray bodies blending against the light brown muck of the bottom. Then they changed course, rolling in a sparkling silver wave.

This moment was nearly 30 years in the making for Ritte (rhymes with “pretty”), a Hawaiian sovereignty activist who’s been a key figure in Native Hawaiians’ efforts to regain access to the hundreds of vast fishponds crafted centuries earlier by their ancestors. Starting around 1200 AD, ancient Hawaiians created a system unique in the world: hybrid, cultivated-wild aquaculture using ponds to trap, raise, and harvest ocean fish. In 1830, the Hawaiian Islands had more than 450 fishponds, and Molokai—known as ‘āina momona, or bountiful land—was the epicenter. Today, 60 half-loops of rock wall are still visible along its southern shore. The fishponds helped to feed as many as 1 million people in the days before European colonization, not far from the 1.4 million who live here now. Today, however, Hawaii imports more than 85 percent of its food, including 50 percent of its seafood.

If Ritte and his comrades succeed in restoring them, Hawaiian fishponds could alter that balance—and also serve as a model for other aquaculture projects around the world. Aquaculture—the farming of fish and other aquatic animals—produces 50 percent of fish and seafood eaten worldwide, according to the U.N. Food and Agriculture Organization, in part because wild fish stocks have been devastated by pollution and overfishing. But industrial fish farms pollute waterways with thick plumes of waste, incubate diseases that can spread to remaining wild fish stocks, and foster massive overuse of antibiotics.

Fishpond activists and scientists working with them to restore these systems believe there is a more sustainable model, inspired by the wisdom of the ancient Hawaiians. Their practices enforced limits on take to ensure that sufficient numbers of fish spawned and resupplied stocks, and used upland plantings to control water quality and nutrient flow into the ponds. “Nobody developed the integration of uplands and seawater—mariculture—like the Hawaiians,” says Barry Costa Pierce, a professor of marine sciences at the University of New England who studies historical systems around the globe and promotes ecological aquaculture.

“The ancients,” adds Ritte, “were fish-rearing geniuses.”