In river ecosystems, in addition to seasonal fluctuations in natural environments, human-induced alterations significantly affect the persistence of local populations of aquatic organisms. Particularly in dendritic watercourses, organisms’ migration routes are mainly confined to the river channel, and structures such as dams and weirs can obstruct movement, leading to the extinction of local populations.
This presentation will introduce four topics that highlight the impacts of human modifications on aquatic organisms from multiple perspectives, including communities, populations, genetics, and isotopes:
1. The interacted effects of instream habitat alternations and flood disturbances in agricultural landscapes on inter-stream migration of caddisfly populations.
2. The effects of the connectivity between paddy canals and rivers on species diversity of floodplain fishes.
3. Evaluation of migration barriers posed by dam reservoirs and the required habitat size for the persistence of fish populations.
4. Restoration of connectivity between upstream and downstream river sections using sediment bypass tunnels and its effects on stream ecosystems.
Through these perspectives, the importance of connectivity between main rivers, tributaries, and agricultural canals will be discussed.