SELECTIVITY OF THREE AQUATIC WEEDS AS DIET FOR NILE TILAPIA (OREOCHROMIS NILOTICUS)

A total of eighty (80) juvenile Oreochromis niloticus were used for the feeding trial, which was conducted over an eight week period. A replicated treatment of ten fish per group were fed three species of aquatic weed, namely Azolla filiculoides (water fern), Elodea sp. (pond weed), Pistia stratiotes (water lettuce) and the control (fed compounded diet) to determine the part of the weeds, which will be selectively consumed. The selectivity was assessed and based on the rate of consumption of the weeds for food and the parts of the plants utilized and the crude protein level of the fish after the experiment. The growth rate of the different treatment groups was also monitored. Azolla filiculoides was the most consumed, the entire plant was utilized followed by Elodea sp., although only the leaves were utilized and Pistia stratiotes was the least consumed and the fishes utilized only the roots. The growth response of the fish to the diets was found to be highest for fish (control) fed compounded ration followed by Azolla filiculoides and Elodea sp. while Pistia stratiotes produced negative growth trend. Proximate analysis of the fish carcass for crude protein after the experiment, show a significant (P Azolla >Elodea>pistia. This study shows that Azolla filiculoides and Elodea sp are viable feedstuff for Oreochromis niloticus, especially when used in conjunction with other feedstuff. An investigation into means of presenting it in an aesthetically acceptable manner is hereby recommended. KEY WORDS: Selectivity, Azolla filiculoides, Pistia stratiotes, Elodea sp., Oreochromis niloticus. Aquatic weeds. African Journal of Livestock Extension Vol.3 2004: 8-1