White Sucker (Catostomus commersoni) Embryo Development, and Early Growth and Survival at Different Temperatures
White suckers (Catostomus commersoni) were exposed from fertilization through hatching to seven constant temperatures from 6.2 through 24.1 °C. High percentages of apparently normal larvae hatched at temperatures from 9.0 through 17.2 °C. Maximum percent hatch occurred at 15.2 °C, while only a few normal larvae were produced at 6.2 °C, and none at 24.1 °C.Growth rates increased from near zero at 10.0 °C to a maximum at 26.9 °C. At 29.7 °C growth fell below the maximum (P < 0.05), and the incidence of spinal deformities was high. Death rates were uniformly low from 15.7 to 26.9 °C and were significantly higher at 10.0 and 29.7 °C (P < 0.05). The rate of net biomass gain for test groups was maximum at 26.9 °C. Net rates of biomass gain declined progressively with temperatures below 26.9 °C until by 10.0 °C the rate of population growth became less than the rate of weight loss through deaths within the population. The temperature producing maximum hatching success, 15 °C, was nearly 12 °C lower than that providing for maximum growth and net biomass gain.Upper thermal 1-, 2-, and 7-day TL50 values for both newly hatched and swim-up larvae, when acclimated to 9 and 10 °C, were between 28 and 29 °C. When acclimated to 15 and 21 °C, they were between 30 and 32 °C.Lower 1-day TL50 temperature values for both groups of larvae acclimated to 21 °C were near 3 °C (< 2.9), 2-day TL50 values were approximately 0.5 °C higher, and 7-day values were 4.8 °C for newly hatched larvae and 6.1 °C for swim-up larvae.