Which parameters – rates of survival or growth – determine the best moment for stocking trout larvae?

Abstract The aim of this study was to determine the best moment to stock trout, Salmo trutta L., larvae into the wild. This goal was accomplished by determining weekly changes in the growth parameters of larvae that were fed in seven variants: on the day of 2/3 yolk sac resorption; from the first week after the day of 2/3 yolk sac resorption; from the second week after the day of 2/3 yolk sac resorption; from the third week after the day of 2/3 yolk sac resorption; from the fourth week after the day of 2/3 yolk sac resorption; from the fifth week after the day of 2/3 yolk sac resorption; from the sixth week after the day of 2/3 yolk sac resorption. Based on our results, we concluded the following: 1) trout larvae are ready to start eating at the time of the resorption of 2/3 of the yolk sac; 2) trout larvae can live without food for three weeks following the resorption 2/3 of the yolk sac without any notable losses; 3) the best moment to stock trout larvae into the wild is in the period from the resorption of 2/3 of the yolk sac to the third week after this resorption, so one week after full resorption. This is the optimal period to stock any waters with trout larvae.