The work was conducted during the growing season of fishes (from April to Octo-ber) in 1978, in Xiamen. The total number of fish studied was 1,596. The preliminary study indicated that the silver carp (Hypophthamichthy molitrix),the big head carp (Aristichthys nobilis) and the grass carp (Ctenopharyngoden idellus)all show the diural rhythm of feeding. The peak of feeding lies at 12:00--20:00. Thegrass carp usually retreats for a certain extent at 16: 00. Seasonally these three fishes takefood vigorously in July and August comparatively greater than in other months. By the method of daily average fullness index, the daily ration (the relation of thetotal weight of food taken in a day to the weight of tbe fish) is 36.2% for grass carp,11. 4% for silver carp and 6. 6% for big head carp, and the duration of feeding withina day is about 20 hours for the grass carp, and 18 hours for silver carp and big headcarp. The rhythm of feeding seems to be influenced by the following factors: the intensityof illumination, the amount of dissolved oxygen, and the temperature of the water. Illu-mination plays a very important role, both directly and indirectly, since it affeclswater temperiture and the amount of dissolved oxygen.