Diel feeding pattern and ration of two sizes of silver barb, Puntius gonionotus Bleeker, in a nursery pond and ricefield

Abstract

The diel feeding pattern, electivity and ration of 4.5-6.9 and 11.5-13.6 cm (total length) silver barb, Puntius gonionotus Bleeker, were investigated along with water quality characteristics in a nursery pond and a ricefield in Bangladesh. Small fish had two peaks (0900-1200 h and 1500-1800 h) in feeding activity in the pond but only one in the ricefield at 1500 h. Feeding at high levels went on throughout the day and on moonlit nights for small fish, and their diet was dominated in both environments by aquatic macrophytes as well as Microcystis, Spirogyra, Oedogonium and Cladophora, rotifers, crustaceans and insects. Large fish fed at low levels, had a single feeding peak during midday in the pond but no clear feeding peak in the ricefield. Large fish consumed macrophytes as well as Microcystis, Anabaena, Spirogyra and Cladophora, and crustaceans (in the pond) or molluscs (in the ricefield). Overall electivity was negative for microalgae. Zooplankton were avoided by large fish in the ricefield. The gastric evacuation time was 1-5 h at 27.5-34.0°C. Daily rations for small and large fish were estimated to be 1.4% and 0.3% of body weight in the pond and 1.1% and 0.6% in the ricefield. Improved fish yields may be achieved by stocking small P. gonionotus where the available food resources include important amounts of zooplankton, and by allowing aquatic macrophytes and weeds to grow in the ricefield or pond after stocking, such that the growing fish can feed increasingly on these.