Critical Stage in Developing Walleye Eggs

Abstract

Egg mortality in walleye Stizostedion vitreum during various developmental stages was monitored at an incubation temperature of 10°C. More than 80% of the mortality occurred during 50–100 h postfertilization or 21–42 temperature units (TU = number of days postfertilization × incubation temperature in oC), particularly during the transformation of germinal layers into various organs of the embryo (i.e., gastrulation–early organogenesis). Mortality declined once the body (head and trunk) of the embryo was formed. This period of high mortality might be considered as a critical stage of walleye egg development. Any environmental stress during this period might cause even higher egg mortality.