Embryo traits at the time of hatch are associated with environmental conditions (temperature) at the time of spawning and when eggs are incubating. Below are data showing mean body length of lake sturgeon at hatch after incubation in water temperatures associated with different river temperatures during early, middle, and late portions of the spawning season corresponding to increasing water temperatures. Sizes of offspring In the “NAT” category represent offspring from eggs obtained from the river substrate under “natural” conditions whereas the other offspring originate from eggs reared in river water but in a stream-side hatchery. Heritability (h²) of body size at hatch is ~0.24 meaning that 24% of the variance in body size is attributed to family.
Free embryos grow by family and as a function of timing of incubation
Free embryos grow rapidly during the period immediately following hatch. Free embryos feed on yolk reserves for a period of several days to weeks and nearly double in size from hatch until the time of emergence from stream substrate and dispersal. The rate of change in body size over time is similar for free embryos from each family. However, body size varies signicantly by family over this period. Free embryos from females spawning earlier in the season remain larger in size than free embroys from females spawning later in the season.
Data on larval lake sturgeon growth (A; total body length) and yolk sac area (B) from the time of hatch (week 1) and weekly through 3 consecutive weeks. Larvae were raised in 3 liter aquaria in the Black River stream-side hatchery. Offspring use yolk sac to develop body mass and sensory abilities (mouth, eyes, Sense of smell) before they are able to feed themselves.