THE INFLUENCE OF TRIPLOIDY AND HEAT AND HYDROSTATIC-PRESSURE SHOCKS ON THE GROWTH AND REPRODUCTIVE DEVELOPMENT OF JUVENILE YELLOW PERCH (PERCA-FLAVESCENS)

We evaluated triploidy induction as a means to sterilize yellow perch (Perca flavescens) and reduce the diminution of growth associated with the onset of sexual maturation. Treatment of perch eggs with heat sho cks (28-30-degrees-C, for durations of 10-25 min, beginning at 2-5 min post-fertilization) or hydrostatic pressure shocks (9000 or 11 000 ps i, for durations of 8 or 12 min, beginning at 5 min post-fertilization ) resulted in triploidy induction rates of 30-70%. In one experiment, juvenile heat-shocked triploid perch grew faster than heat-shocked dip loids. In a second experiment, heat-shocked triploid perch grew slower than unshocked diploids up to 25 g, but subsequent growth of fish fro m the two groups was not different. In a third experiment, unshocked d iploids grew faster than fish subjected to either heat or pressure sho cks, and among shocked fish, triploids outgrew diploids. Histological inspections revealed that gonadal development of juvenile triploid per ch of both sexes was retarded compared to that of diploids. These find ings show that heat and pressure shocks exert a negative influence on growth that is independent of changes in ploidy, and that triploid per ch may have the potential to outgrow diploids if the negative effects of such shocks can be avoided.