Feeding Habits of Mixed Cyprinid Species in a Chinese Integrated Fish Culture Pond: Change in Planktivorous Density Induces Feeding Changes in Planktivorous Carps

Abstract

Gut contents of six cultured cyprinid species were sampled and their chlorophyll and chlorophyll derivatives were measured to quantify fish feeding in a Chinese integrated fish culture pond. The densities of planktivorous (silver and bighead carp) and benthic-feeding (crucian and common carp) fish fry stocked in the pond were only 12% and 43%, respectively, of those in our previous pond study (TAKAMURA et al., 1993). High ratios of chl. b/chl. a or phaeophorbide a/chl. a were good indicators of the dependence on aquatic plants of herbivory or zooplanktivory, respectively. Phaeophytin a seemed to be a good index of herbivory on decomposing aquatic plants. Grass carp and blunt snout bream fed mostly on aquatic plants. The feeding habits of silver and bighead carp were very similar. These two planktivorous fish ingested Zooplankton, phytoplankton and plant fragments derived from faeces of grass-eating carps. Silver carp were more dependent on Zooplankton and bighead carp were less dependent on plant fragments in this pond as compared with those from the pond in our previous study (TAKAMURA et al., 1993). Common carp were largely dependent on plant fragments. Crucian carp utilized both plant fragments and Zooplankton. The feeding habits of benthic carps did not differ from those in our previous pond study. Regardless of some changes in the feeding habits of planktivorous carps, both planktivorous and benthic-feeding cyprinids reared in this pond seemed to be supported by plant fragments, and were probably nourished by microorganisms attached to those plant fragments (IWATA et al., 1992). © 1994, The Japanese Society of Limnology. All rights reserved.