Feeding selectivity and growth of Nile tilapia (Oreochromis niloticus L.) fed on temperate-zone aquatic macrophytes
Feeding selectivity of Nile tilapia (Oreochromis niloticus L.) juveniles (9.3–20.9 g) to four aquatic macrophyte species and tilapia growth were studied in 4 consecutive experiments. Plant diet was provided to 8 tanks containing 20 fishes for 5 days. The fish were fed a carp diet between 4 experiments for 14 days. The consumption of 4 aquatic macrophyte species differed significantly [F(3,252) = 39.6; P < 10<sup>–6</sup>]. Elodea canadensis was the most preferred plant (Chesson selectivity index = 0.50 ± 0.05, n = 4). Potamogeton pectinatus and Spirodela polyrhiza were consumed with about equal preference. Myriophyllum spicatum was the least preferred species. Elodea canadensis contained relatively more phosphorus, potassium and ash than the other three species. The daily plant dry weight intake ranged between 0.79 and 2.26% of body weight. The fish grew during the first two experiments (SGR = 2.54 and 3.18%/d, respectively), but lost weight during the 3rd and 4th experiments (SGR = –1.75 and –1.71%/d, respectively).
