Growth Comparisons of Diploid and Triploid Grass Carp under Varying Conditions

Growth of fry and fingerling diploid and triploid grass carp (Ctenopharyngodon idella) was evaluated under a variety of experimental situations that involved high and low stocking densities and various levels of food availability. Diploid grass carp grew faster and had significantly (P < 0.05) higher condition factors in every situation where they were grown together with triploid grass carp. When diploid and triploid grass carp were grown in separate pools and fed to satiation with duckweed, there were no significant differences (P < 0.05) in growth, condition factors, food conversions, or rates of food consumption. The difference in the rate of growth between diploid and triploid grass carp can be exploited to presegregate diploid from triploid fish, thus reducing the time spent certifying ploidy with a Coulter Counter (R).