Fish species composition of temporary small lentic habitats in the floodplains of the Shubuto River System : Factors affecting species richness and suggestions for conservation and restoration

Abstract

We investigated the ichthyofauna of 18 temporary lentic water bodies along the river (floodplain sites), as well as reference sites including two isolated ponds, two oligotrophic wetland sites dominated by sphagnums, and four lentic tributaries (non-floodplain sites) in the Shubuto River System, SW Hokkaido. In total, 16 fish species belonging to eight families were recorded. Cluster analysis revealed three clusters containing both floodplain and non-floodplain sites and one cluster consisting of only floodplain sites. Three species, Lethenteron camtschaticum, Lethenteron sp. N, and Gymnogobius opperiens, were indicator species that were significantly associated with the only-floodplain cluster. Nestedness analysis showed that the fish species composition of the floodplain sites was significantly nested. Multiple regression and canonical correlation analyses demonstrated that fish diversity in floodplain sites was positively affected by water surface area and water depth and negatively affected by channel distance from the ocean. With reference to the results of the present study, we discussed the design of ecological restoration measures for the floodplains along the Shubuto River, which will contribute to the conservation of fish fauna.