sentences:  They found that Nile perch, introduced by the British sixty years ago, have decimated native fish populations, leading to malnutrition in the lakeside communities.She helped to set up artificial fish ponds to raise carp, which had disappeared from the local diet.The United States Agency for International Development sponsored the digging of the ponds and sent villagers to Kibbutz HaMa'apil in Emek Hefer to learn spawning techniques.