Freshwater eel are catadromous with their juvenile growth stage occurring in estuaries, river and lakes, and with their spawning areas begin offshore in the ocean. This study investigates the relationship between temporal and spatial changes of glass eel catches at Yilan, Tamsui, Chiayi, and Pingtung, respectively. The daily catch, fishing time and fishing methods will record to determine the location characteristics of glass eel resources. The glass eel specimens will be collect monthly during the fishing seasons to identify morphological differences of the eel.