PHYTOPLANKTON,ESPECIALLY DIATOMS,IN THE GUT CONTENTS AND FECES OF TWO PLANTIVOROUS CYPRINIDS-SILVER CARP AND BIGHEAD CARP

In order to clarify whether the planktivorous silver carp and bighead carp can collect phytoplanktonas small as Cyclotella(<20μm)in Donghu Lake,studies on phytoplankton in their gut contents and feceswere made in 1990.The fish were cultured in both net cage in Donghu Lake and aquaria with the lakewater.Past the intestine,the average valve diameter of Cyclotella changed little.The average ratio of emptyfrustule of Cyclotella to total Cyclotella in the foregut contents of the fishes were 1.8—1.9 times higherthan that in the lake water,but changed little from foregut to feces.The aquarium experiment showedthat both carps could collect particles as small as 8-10μm, which was obviously narrower than the dis-tance between their gill rakers.Probably,secretion of mucus plays an important role in collecting suchsmall particles

PHYTOPLANKTON, ESPECIALLY DIATOMS, IN THE GUT CONTENTS AND FECES OF TWO PLANTIVOROUS CYPRINIDS-SILVER CARP AND BIGHEAD CARP