Maternal influences on variation in egg sizes in temperate marine fishes

We examine the variation in egg sizes of marine teleosts and evaluate the maternal contribution to this variability. At the species level, egg sizes in 309 North Atlantic fishes range from 0.3 to 18.0 mm diameter (median = 1.1), size at hatching varies directly with egg size, and large adult size is associated with large eggs but the relationship is weak. Within populations, egg sizes are distributed normally with a median coefficient of variation of 4% (n = 56 species). Egg size varied among females in all cases for which female-level data were found. Estimates of the variance components of egg size due to females were found for three species and, as a percentage of total variance, are 71% for capelin, Mallotus villosus, 46% for winter flounder, Pleuronectes americanus, and 35% for Atlantic cod, Gadus morhua. For cod, which spawn multiple egg batches per year, an additional batches-within-females component was estimated to be 26%. Size at hatching also differs among sibgroups and is generally directly related to egg size at the individual level. We modelled fish growth by allowing individuals to grow at exponential rates from a normal distribution of initial sizes. Comparing size variation in model fish to empirical evidence suggests that variation in initial sizes, propagated by growth, could account for a large fraction of the size variation observed months after hatching in natural populations. We view size variation in young marine fishes to be largely of maternal origin and environmentally modulated, which if true has special consequences for fisheries and aquaculture.