Shubuto River has preserved relatively high integrity of a fresh-aquatic ecosystem and longitudinal connectivity, while its floodplains have largely lost by past agricultural development. We investigated fish abundance at 23 small lentic habitats occurring temporary in remaining along the river during the spring and autumn seasons in 2011.

Twelve diadromous and potadromous fish species spawning in lentic or lotic habitats were found during the survey. Using structural equation modeling, abundance of each fish species was regressed on five explanatory variables, including river distance from sea, incidence of drying out, cover condition (forest floor vs. open wetland), water depth and surface water area.

Except for pond loach and chum salmon, water depth and surface water area positively significantly affected the abundance. Incidence of drying out significantly negatively affected arctic lamprey and ninespine stickleback.

These results suggest that various fishes utilize even small lentic habitats that temporally occur in remaining small floodplains, and especially depend on the deep, large and more persistent lentic habitats. Creation of such habitats should be included to be the major targets of the floodplain restoration planned for near future.