Assessment of the Effect of Duckweed (Lemna minor) on Monosex Niletilapia (Oreochromisniloticus) Farming at Ambo, Ethiopia

The effectiveness of duckweed fed monosex O.niloticus farming was assessed for 120 days from July-November, 2017 based on 35 young fish stockedin geo-membrane lined ponds ofeach 3*3 m area and 1.5m depth. Five dry diets consisting of 0%, 25%, 50%, 75%, and 100% duckweed formulated at 30% crude protein were fed to young fish (25±10.6g-32±16.6g) in the form of pellets at 5% body weight twice a day each with two replications where the 0% (wheat bran and corn bran) served as control. Mortality was recorded on daily basis whileweight gain,pond water temperature, and pH were determined every fortnight. Nutritional values of the diets and carcass of fish grown on the dietswere assessed using standard laboratory procedures.Maximum percentage average growth and survivalwas demonstrated by fish grown on 50% duckweed supplemented feed followed by those fed on 25% duckweed. Growth performance and percentage survival of fish grown under different treatments as well as that between fish fed on control diet and the experimental diets were significantly different (p<0.05). Average crude protein and lipid contents of the fish grown on 25% duckweed are relatively higher as compared to those grown on the rest diets. Assessment of the crude protein of fish grown on various levels of duckweed supplemented feed indicated a weak positive correlation (r2=0.011). Thus, the results showed that a diet comprising up to 50% duckweed could be used as a complete replacement for traditional feed in the diet of O. niloticus.