Supplementation of four non-conventional aquatic weeds to the basal diet of Catla catla and Cirrhinus mrigala fingerlings: Effect on growth, protein utilization and body composition of fish

Background. Our previous study has shown that four aquatic weeds viz. Asian watermoss, Salvinia cucullata; water spinach Ipomoea reptans; water chestnut, Trapa natans; and lesser duckweed, Lemna minor from north-east India are important sources of proteins, vitamins and minerals, suitable for incorporation in fish diet. The aim of the present study was to compare the efficacy of these aquatic weeds based formulated diets on growth, feed utilization and nutrient turnover from feed to fish flesh of fingerlings of two species of Indian major carps: catla, Catla catla (Hamilton, 1822), and mrigal, Cirrhinus mrigala (Bloch, 1795). Materials and methods. The fingerlings were hand-sorted and distributed in 15 glass aquaria (each having 50 l capacity) at a stocking density of 5 fishes per aquarium. Five formulated diets (containing 26%–28% of crude protein approximately) were prepared and analyzed for proximate composition. The diets were fed to catla and mrigal fingerlings in triplicate treatments at the rate 3% of body weight for 60 days and fish performance in terms of growth, feed utilization and carcass composition was evaluated. Results. The whole body composition and energy content of C. catla fingerlings before and at the end of feeding trials did not differ significantly (P > 0.05), however, the proportion of crude lipid content was high when fed with diet F2 (P < 0.05). In case of C. mrigala, crude protein, as well as lipid contents, were significantly higher in all the groups of fish at the end of experiment as compared to the initial fish. The hepatic- as well as the muscle tissues of catla and mrigal fingerlings fed the diet F2 (containing I. reptans) displayed high contents of crude protein and vitamin E (P < 0.01). Interestingly, although no difference in muscle glycogen level in C. mrigala was observed irrespective of the diet fed however, muscle and liver glycogen contents in Catla catla fingerlings fed F2 diet was significantly higher compared to glycogen contents of these tissues of initial fish or fish fed with control diet. Conclusion. Presently reported study suggests that I. reptans, being a rich source of nutrients, is suitable for incorporation in fish diet for C. catla and C. mrigala fingerlings.