The changes of hydrological regimes due to flow regulations such as reservoir operations have significant impacts on the aquatic ecosystem, and fish population dynamics is an important indicator to quantify these impacts. It is well known that different individual has different responses and adaptabilities to the environmental changes. Even for one individual, it could experience different life stages including embryo, larva, juvenile, young, adult and aged, which would obviously causes the dissimilarities among their preference to the living conditions such as water depth, flow velocity, dissolved oxygen concentration and water temperature. Therefore, this study took the previous individual based fish model as basis and focus on the age effects. The model tracks the daily growth, mortality and movement of each individual for up to six life stages for a single generation. The developed model was applied to a compound channel of the Lijiang River where the aquatic ecosystem has been largely affected by multiple reservoirs operations in the upstream. Two species are modeled that are the Chinese Idle and Crucian. The verified model not only provides supports to optimize the reservoir operation schemes but advances the development of individual-based models.