Intra-Individual Egg Size Variation Among Populations of Walleye in the Great Lakes and Its Relationship to Maternal Characteristics

Egg size and egg size variability can have important implications for larval fish success, and may vary intraspecifically through adaptive and plastic mechanisms.  While many studies have documented the influences of maternal effects and environmental conditions on egg size variation within populations, few have investigated the impacts of these processes on egg size variation within individuals.  Some populations may express more within-individual variation than others because they experience greater environmental unpredictability.  Should intra-individual egg size variation be related to maternal traits, it could have important management implications.  We evaluated differences in intra-individual egg size variability among several populations of walleye (Sander vitreus) from 2007-2012. There was no relationship between within-female egg size variability and maternal age or total length.  Within years, within-individual egg size variation differed significantly among populations, which may reflect different environmental conditions experienced by each population.  Year to year, levels of variation in some populations were relatively consistent, while others varied significantly.  Populations with low intra-individual variability may experience relatively homogenous environments each year.  In contrast, egg size in highly variable populations may be a phenotypically plastic trait.  Alternatively, females may produce eggs of a diversity of sizes to maximize their reproductive fitness in an unpredictable environment.