Located on an island in the Guadalquivir river, 10 miles (16km) inland from the Atlantic, Veta la Palma produces 1,200 tons of sea bass, bream, red mullet and shrimp each year. Yet unlike most of the world’s fish farms, it does so not by interfering with nature, but by improving upon it. “Veta la Palma raises fish sustainably and promotes the conservation of birdlife at the same time,” says Daniel Lee, best practices director for the U.S.-based Global Aquaculture Alliance. “I’ve never seen anything quite like it.”

With wild fish stocks declining precipitously around the globe, thanks to overfishing and climate change, aquaculture has emerged as perhaps the only viable way to satisfy the world’s appetite for fish fingers and maki rolls. In the next few years, consumption of farm-raised fish will surpass that caught in the wild for the first time, according to the United Nations Food and Agriculture Organization. But most fish farms — even ones heralded as “sustainable” — create as many problems as they solve, from fecal contamination to the threat that escaped cultivated fish pose to the gene pool of their wild cousins.

Veta la Palama is different. In 1982, the family that owns the Spanish food conglomerate Hisaparroz bought wetlands that had been drained for cattle-farming and reflooded them. “They used the same channels built originally to empty water into the Atlantic,” explains Medialdea. “Just reversed the flow.” Today, that neat little feat of engineering allows the tides to sweep in estuary water, which a pumping station distributes throughout the farm’s 45 ponds. Because it comes directly from the ocean, that water teems with microalgae and tiny translucent shrimp, which provide natural food for the fish that Veta la Palma raises.

By hewing as closely as possible to nature, the farm avoids many of the problems that that plague other aquaculture projects. Low density — roughly 9 lb. (4 kg) of fish to every 35 cu. ft. (1 cu m) of water — helps keep the fish free of parasites (the farm loses only 0.5% of its annual yield to them). And the abundant plant life circling each pond acts as a filter, cleansing the water of nitrogen and phosphates.