Influence of egg size and parental genetics on the metabolic rate of Chinook and pink salmon embryos.

Freshwater environments are experiencing rapid changes in seasonal temperature and water flows that could impact threatened aquatic species. Environmental stressors experienced by mothers can influence the size and quality of fish eggs creating downstream effects on larval fitness. Cool water fish species like Pacific salmon with extended periods of embryonic development may be especially vulnerable to changing environmental conditions. To gain insight into the factors influencing embryonic physiology in fish, the relationship between parental genetics, egg size and embryo metabolism was examined in developing Chinook salmon (Oncorhyncus tshawytcha) and pink salmon (Oncorhyncus gorbuscha) embryos, as these species exhibit distinct differences in egg size and life history strategies. Egg size was found to have a relatively limited effect on embryo metabolism with parental genetics having a larger effect on the embryos of these species. Maternal genetics influenced embryonic metabolic rate more in the early stages of development than at later stages of development. These findings suggest that parental genetics or epigenetics is a key factor determining the metabolic rates of salmon embryos and that genetics should be considered when seeking to understand how environmental change will impact threatened fish species, like Pacific salmon.