The largest fish in South America, called arapaima, live in stagnant flood plains of Amazonian rivers. But the 2-meter-long animals are highly vulnerable to spearfishing and gillnets, because they come up to fill their primitive lungs with air every 5 minutes or so. A new study of fishing villages in Brazil, published online in Aquatic Conservation: Marine and Freshwater Ecosystems, finds that the fish have vanished from rivers around 19% of the villages. It's nearly extirpated from another 57% of villages, LiveScience reports. The good news is that the fish are 100 times more abundant in communities that have put fishing rules, such as catch limits.