The effects of different temperatures on growth and survival of yellow perch larvae, Perca flavescens (Michill, 1814)

Yolk- sac reasorption, survival and growth of yellow perch larvae, were compered at different temperatures. Three groups of fish were raised at constant temperature of: 12 (temerature of the incubation), 15, and 18°C. For the fourth group the temperature was slowly elevated each day by 1°C, from the hatching till the completion of yolk sac resorption (12-17°C). The rate of the yolk sac resorption was very high and significantly reflected by the growth in all treatments during the first 24 hours, when 4/5 of the yolk was depleted. At the temperature of 12°C resorption was completed 150 hours after hatching, and at 18°C, the highest temperature in the experiment, 124 hours after hatching. Statistical analysis of the rate of yolk sac resorption shows that the coefficients of the exponential regressions discribing the depletion at 12°C and 12-17°C are statistically different from the other temperatures. Distribution of total lengths of larvae during the time of yolk sac depletion approximated by exponential equations showed no significant statistical difference in growth at different temperatures (ANOVA, p > 0, 01). Optimum growth temperature, estimated by maximizing the temperature - growth rate relationship function, was 13, 9°C at 0.01044 mm/ hour maximum growth rate. No significant difference in survival was recorded between groups kept at 12, 15 and 12 - 17°C, but survival during the period of yolk - sac resorption was significantly lower for the larvae raised at 18 °C (ANOVA, p > 0, 01).