Japanese eel, Anguilla japonica, is one of the most important species of fish culture in Taiwan. Elvers for the culture are collected from estuaries during their upstream migration in winter. Due to their unpredictable supply, the elvers were frequently imported from foreign countries to meet the demand. To increase the natural production of the elvers, hormone-induced maturation eels have been released by the Taiwan Fisheries Research Institute since 1976, and the eels released have been tagged since 1987 to study their migration route, growth and other biological characteristics. This paper describes the hormone-induced maturation processes, tagging techniques, and recovery status of the eel.