 Some of these, including tilapia and ningu ("Labeo victorianus"), had already declined in the first half of the 20th century due to overfishing.To boost fishing, several species of non-native tilapia and Nile perch were introduced to the lake in the 1950s.Nevertheless, the natives continued to dominate fisheries until the 1970s where their decline meant that there was a strong shift towards the non-native Nile tilapia (now 7 percent of catches), non-native Nile perch (60 percent) and the native Lake Victoria sardine (30 percent).