ON THE DISTRIBUTION AND HATCHING OF RESTING EGGS OF ROTIFER IN FISHPONDS

This paper embodies the results of field surveys on the abundance and distribution of the resting eggs of rotifer in fishponds and the experimental investigations on the effects of some external or internal factors on the hatching of the eggs.The number of the resting eggs in the upper 5 cm depths of the bottom mud in the fishponds is estimated at twelve thousands to five millions per square meter, of which only about 1—2% lie on the free surface. The eggs may normally be incubated under such conditions where water temperature being 10—40℃, pH value 4.5—11.5, salinity less than 8.5‰ and the O2 content above 0.3 mg/l.The relationship between the number of rotifer population and their resting eggs and the ways to increase the abundance of rotifer in fishponds are discussed.