Genetic and maternal variation in early growth in the Atlantic silverside Menidia menidia

In the early life histories of many fish species, larger individuals have lower mortality rates and, as a consequence, growth is thought to be a primary determinant of recruitment. Although much is known about environmental influences on growth in the early life history, far less is known about genetic and maternal contributions. As the relative contributions of maternal, genetic, and environmental effects determine how populations respond to selective harvest, evaluating their magnitudes is an important step in constructing evolutionarily sustainable harvest strategies. Using Atlantic silversides Menidia menidia as a model organism, we conducted a full-factorial breeding study to measure maternal and genetic contributions to size at age through the first 2 wk of life. A total of 418 full- and half-sib families were raised in a common environment, and body lengths were recorded at 1, 5, 10, and 15 d post-hatch. Maximum likelihood was used to estimate the genetic and maternal variance components. Heritability for size at age was between 0.10 and 0.25, and increased with age. At hatch, non-genetic maternal contributions were similar to 7 times greater than the genetic contributions to size, but decreased with age. These significant genetic and maternal contributions to size at age indicate substantial potential to respond to selection, with subsequent population dynamic consequences.