ABSTRACT
In the southern regions of the USSR, phytophagous fish have been introduced more and more into pond culture, primarily grass carp and silver carp. In addition to these species, and in combination with them and common carp, bighead has also been included in pond culture. Bighead feeds on phytoplankton and on zooplankton; the total weight of the two constitutes 50% or more of the diet. Silver carp feeds on phytoplankton and detritus. It prefers diatoms and green algae but consumption of blue-green algae is poor, as it avoids many of these species. Grass and silver carp and bighead do not breed in ponds and the only method for obtaining eggs is pituitary injections. Male gonads, although they mature without pituitary injections, nevertheless produce a larger quantity of milt with artificial stimulation. The periods of work on artificial breeding for individual species of phytophagous fish are not the same because maturation of the sex products occurs at different periods.
