Comparison of the usefulness of the silver carp and the bighead carp as additional fish in carp ponds

On the basis of fishery results and food analyses of the silver carp, Hypophthalmichthys molitrix, and of the bighead carp, Aristichthys nobilis, it was found that the latter species is less useful for intensive rearing in ponds jointly with the common carp. Although the bighead carp, due to its rapid growth rate, gave a higher level of production than the silver carp at the same stocking densities, the drop in common carp production with bighead was so considerable that there are doubts as to the usefulness of joint rearing of the two species in ponds. Comparisons of the amount and composition of food of the silver carp and the bighead carp lead to the conclusion that food competition of the latter species with respect to the common carp is considerably greater. Although neither silver carp nor bighead carp consumed feed given to the common carp (sorghum), and detritus was the main dietary component of the two former species of fish, the proportion of invertebrates in the food of bighead carp was greater and the components more similar to the food of the common carp. The silver carp consumed smaller zooplankton species, mainly Bosmina longirostris and rotifers, which were of no significance as food for the common carp. The bighead carp consumed large Cladocera and Copepoda species, and also Tendipedidae larvae, i.e. organisms constituting the basic component of the food of common carp.