Daily food consumption and feeding rhythm of silver carp ( Hypophthalmichthys molitrix) during fry to fingerling period

Abstract

Daily food consumption and feeding rhythm of silver carp ( Hypophthalmichthys molitrix) from fry to fingerling (6.6–195 mm in total length) were measured from June 1985 to August 1986 using a method of intestine filling index. Absolute food consumption (expressed as wet weight of food consumed per fish each day) was positively related with the body weight of silver carp, and relative food consumption (expressed as wet food consumed as percentage of fish body weight) decreased with increases in body length of the fish. The relative food consumption of silver carp averaging 6.6–8.6 mm in total length was 139.2±6.6%; as the fish grew, relative food consumption reduced to 30.7±3.3%. However, when total length reached 21.7–26.0 mm, relative food consumption increased to 63.2±5.0% ( P<0.05), but decreased again to 16.5±1.2% for fish 132–195 mm in total length. The variation in food consumption was due to a change in feeding habits from zoo-plankton to phytoplankton and the difference in nutritive contents of the plankton consumed by silver carp. An obvious daily feeding rhythm was observed. The fish did not feed from 22.00 h to 04.00 h, but from 09.00 h to 11.00 h and 17.00 h to 21.00 h the fish fed actively. The difference in intestinal filling indices between the feeding peak and low feeding level became less and less as the fish grew. The reason for this might be improvement in digestion.