ABSTRACT
Diurnal variation in feeding intensity was similar to that found in natural conditions, with feeding intensity peaking at 1400 h. Dissolved oxygen (DO) levels were responsible for the variation of feeding intensity at the different times, but not for the feeding rhythms. The experiments are conducted under controlled conditions in order to study whether diurnal feeding rhythms existed under different DO levels, and to assess to what extent low DO levels affected the feeding intensity of silver carp and bighead carp. The feeding rhythm was measured at different, but constant, dissolved oxygen levels over the 24 hour period. The water used in the experimental tanks was drawn directly from the fish pond, stored in a high-level tank, and then dispensed into the experimental tanks. In the experiments the difference in DO concentration between experimental treatments was about 20 to 30%, and the corresponding differences in the length of time needed for evacuation of the food was about one hour.
