Abstract
The relationship between nutritional condition, indicated by storage lipid content, and diel vertical migration of Daphnia galeata in Lake Kizaki was investigated in July 1991. The D. galeata population was divided into two groups, i. e., upper and deep layer groups during daytime. The upper layer group consisted of juveniles and adults of poor nutritional condition, while the deep layer group consisted only of adults of better nutritional condition. Diel changes in the vertical distribution of D. galeata revealed that adults in the deep layer performed diel vertical migration, whereas juveniles and adults in the upper layer did not migrate vertically. These result implied that adult D. galeata with better nutritional condition performed vertical migration in the context of their life cycle.
