National Research Institute of Fisheries Science (NRIFS) has carried out the long term monitoring program for radioactive pollution in marine organisms caught around Japan in order to confirm the safety of marine organisms as food source. Recently, the effective ecological half-lives have been introduced to estimate the recovery time from radioactive pollution. In this study, the effective ecological half-lives of Cs-137 for some fishes were calculated from our monitoring data. It is known that fish species have each effective ecological half-lives. However, it has been unclear what change these half-lives of Cs-137 for fishes. Fishes intake Cs-137 through food chain and directly from their surrounding seawater. Therefore, the effective ecological half-lives of Cs-137 for some fishes would be controlled by the effective environment half-lives of Cs-137 for their surrounding seawater. There is difference in the effective environment half-lives between the open ocean and the coastal seawaters. Some fishes move between the open ocean and the coastal areas, and therefore their effective ecological half-lives are influenced by the effective environment half-lives for seawaters of both areas. Consequently, the rate of the influence by seawater in each area would produce the differences in the effective ecological half-lives among fish species.