Theoretical winter incubation periods and responses of embryo demographics under normal (2.0 °C; blue) and hypothetical warm (5.0 °C; orange) winter thermal regimes. The shaded regions indicate spawning periods (left) and hatching periods (right) that may occur between 4 and 5 °C. The 2.0 °C temperature regime is water temperature data collected from Lake Superior at 10-m depth in 2018.