Effect of Lowering Water Temperature on Hatching Time and Survival of Lake Trout Eggs

Tests were conducted to determine the effects of low incubation water temperatures on lake trout (Salvelinus namaycush) egg mortality and hatching time. Eggs incubated at 9.8°C hatched in 58 d and required 570 temperature units (degree-days above 0°C); eggs incubated at 6.4 and 1.8°C hatched in 90 and 196 d and required 572 and 352 temperature units, respectively. Eggs incubated at 1.8°C took 138 d longer to hatch than those incubated at 9.8°C, but there were no significant differences in percent mortality among the three treatments. In a second test, hatching time of eyed eggs held in 0.9°C water was retarded 40 d compared to eggs held in 8.0°C water.