EFFECTS OF STRESS ON THE REPRODUCTIVE-PERFORMANCE OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

We investigated the effects of stress over the final stages of sexual maturation on the reproductive performance of female rainbow trout, On corhynchus mykiss. Stress was administered over the period of early vi tellogenesis (1.5 mo), late vitellogenesis-final maturation (1.5 mo), or during both periods (3 mo), Each stress treatment and control was t riplicated, with eight females in each replicate (n = 24 fish per trea tment). The eggs and progeny of each female were kept separate, and ob servations were made for 4 mo after transfer to rearing tanks, Fish th at experienced stress during final maturation and those that were unde r stress during the whole experiment ovulated on average 2 wk earlier than the control group, In contrast, fish stressed during the period o f early vitellogenesis ovulated at the same time as controls, Absolute fecundity and fertilization were not significantly affected in any tr eatment group, but significant differences in relative fecundity were found. Stress applied early in vitellogenesis resulted in smaller eggs and swim-up fry, No significant differences were found in juvenile we ight 8 wk after hatching, Furthermore, we found no differences in surv ival of the progeny or resistance to the fish pathogen Vibrio anguilla rum, Thus, mild acute stresses applied to rainbow trout females may af fect certain reproductive performance parameters such as timing of ovu lation and relative fecundity; however, the progeny of such stressed f emales perform as well as controls with regard to juvenile growth and disease resistance.