this report, prepared by journalists chris berdick and steve sapienza and narrated by our hari sreenivasan produced in partnership with the pulitzer center on crisis reporting. reporter: on cambodia's lake lake tonle sap, in one of the most productive fresh water ecosystems in the world. this fisherman starts his day much like his neighbors, with family breakfast. then the father of five paddles a nearby man grove to reach the gilnet he set the night before. he and others catch about 350,000 tons of fish from this lake every year, a vital resource in a country where 75% of the protein people eat is fish. at a nearby fish landing, workers sort the day's catch. most of the haul is minnows known as money fish which go for 25 to 50 cents a kilogram. they're used to make fermented fish paste, a staple in cambodian cooking. the importance of fish is deeply rooted in the cambodian culture. chiseled into the medieval temple are many of the same fish that are harvested from the tonle sap today. the astounding number and diversity of fish here has long attracted researchers like american biologist l