Adaptive, Plastic, and Maternal Effects on Egg Size, Egg Quality, and Egg Size Variation in Great Lakes Walleye

Egg size is influenced through complex interplay of long-term adaptation to local environments and short-term plastic responses to annual variability.  Maternal effects also play a potentially important role, as larger females appear to produce larger, better-provisioned offspring than smaller females.  Superimposed on egg size variation among stocks, egg size variation within females may represent energetic or adaptive trade-offs that influence individual reproductive success.  As variation in egg characteristics can have important implications for offspring survival, fluctuations in these traits may impact population-scale recruitment dynamics.  We evaluated the importance of adaptive, plastic, and maternal influences on egg size and egg size variation across six walleye Sander vitreus populations from 2007-2014.  Egg size was temporally conserved within stocks, indicating that adaptation to local environments is a major force driving egg size determination.  Maternal influences on egg size were weaker, more variable, and potentially related to variability in climate, meaning annual environmental conditions may influence egg size variation through impacts on maternal condition.  Our results suggest that anthropogenic stressors such as climate change could impact not only short-term egg production, but also spur adaptive changes in egg size among populations, which could have unpredictable consequences for future variation in walleye recruitment.