Due to a malfunctioning incubator, when 2 °C embryos reached constant fin flutter, incubation temperature was changed to 3.9 ± 0.3 °C until hatching. This resulted in an average incubation temperature throughout development of 3.3 ± 0.2 °C, and thus we refer to hatchlings from this group as being incubated at 3.3 °C throughout the manuscript.