Environmental and genetic effects on larval hatching time in two coregonids

Hatching time (HT) of autumn-spawning fishes depends strongly on the egg incubation temperature and especially on the warming of water in spring, which synchronizes the hatching with ice-out despite the large inter-annual variability in spring phenology. However, the relative roles of genetic and environmental effects on the HT have rarely been explored. We studied experimentally the parental effects on the HT and size of vendace (Coregonus albula (L.)) and whitefish (C. lavaretus L.) larvae under short and long winter conditions using a full-factorial breeding design. Both parents significantly affected the HT of vendace, mostly by additive genetic effects, and the difference between short and long winter treatment was also significant. In whitefish, the female x male interaction was significant, implying non-additive genetic effects. The maximum range of the HT of eggs between parent pairs within certain winter condition was 3 weeks and was clearly lower than the potential range for the temperature-adjusted HT. The size of eggs or hatched larvae did not correlate with the HT in either of the species. The variation in HT between eggs from different parents creates a basis for genetic adaptation to climate change and for local adaption of populations in their thermal environments.