Pocantico Hills , New York ( CNN ) -- Oil-tainted seas , oxygen-deprived zones , overfishing , mercury poisoning ... these days , the search for safe and ethical seafood is enough to unnerve any pescetarian . For chefs , it does n't just mean crossing another fish off our menus . The question has become how do we keep fish on the food chain ? I found one answer last year , at a fish farm called Veta la Palma . Veta la Palma is in southwestern Spain , at the tip of the Guadalquivir River . Until the 1980s , the land was in the hands of the Argentineans . They once raised cattle in what were essentially wetlands , and they did it by draining the land . They built a series of canals and siphoned the water off the land and into the river . But they could n't make it work . Economically and ecologically , it was a disaster . In draining the land , they killed 90 percent of the bird population . And so in 1982 , a company with an environmental conscience purchased the land . What did they do ? They reversed the direction of water flow in the canals ; they literally flipped the switch . Instead of using the channels to pump water out , they pulled water in , flooding the canals and creating a 27,000-acre fish farm of sea bass , mullet , eels , shrimp and sole . In doing so , the company reversed the process of ecological destruction . The farm is incredible , with hundreds of miles of flooded canals and thick marshland , teeming with life . I stood there not so long ago with Miguel Medialdea , Veta la Palma 's head biologist . According to Medialdea , it 's such a rich environment that the fish eat what they 'd be eating in the wild . Because the system is so healthy , it 's totally self-renewing . But Veta la Palma is not just a fish farm ; it 's also a bird sanctuary . Today there are 600,000 birds on the farm from 250 species . It 's become one of the most important private estates for bird life in Europe . You might think a thriving bird population is the last thing you 'd want on a fish farm ( Veta la Palma loses 20 percent of fish eggs and baby fish to the birds ) , but for Medialdea , it 's a point of pride and a testament to the company 's success . `` We farm extensively , not intensively , '' he told me . `` It 's an ecological network . So the healthier the birds , the better the system . '' But the truest measure of their success is much simpler : flavor . Veta la Palma 's fish was the most delicious I 'd ever tasted , starting with the skin . I do n't like fish skin -- not seared or crispy . I almost never cook with it . Yet when I tasted it at Veta la Palma , it tasted not at all like fish skin . It tasted sweet and clean , like taking a bite of the ocean . I mentioned it to Medialdea , and he nodded . `` The skin acts like a sponge , '' he explained . `` It 's the last defense before entering the body , and it evolved to soak up impurities . But there are almost no impurities in our water . '' And that 's an understatement . The water flows into the canals from the Guadalquivir River , carrying all the things rivers tend to carry these days -- chemical contaminants and pesticide runoff -- and when it flows back out , it 's cleaner than when it started . The system is so healthy it purifies the water . The purification is not just for the fish , but for us as well . That river water eventually dumps into the Atlantic . Sure , it 's a drop in the bucket , but I 'll take it . The opinions expressed in this commentary are solely those of Dan Barber .
With compromised , overfished seas , Dan Barber puzzled over how to keep fish on food chain . He says he visited fish farm in Spain that restored water flow , fish populations to wetlands . The farm is ecologically balanced , with abundant fish and 250 bird species , he says . Barber : The farm 's system is healthy again -- and the fish it produces are delicious .