The objective of this study is to investigate the characteristics of aquatic animals, especially fishes in the irrigation and drainage channnels, during paddy rice growning season and to propose the criteria on the ecologogal environment for each fishes. First, observation on the lives and populations of fishes were conducted and evaluate the environmental suitability for fishes in each channnels. Second, lives of some popular fishes in the channels were studied. Third, using the data obtained, ecological criteria for each fishes were discussed. Fourth, considering the weir, drop and concrete lining in irrigation channnels are obstacles for the aquatic animal movement, new techniques to improve the living condition for those animals were proposed.