Abstract
Based upon the "Model projects for promotion of enhanced environments for ascent of fish" that was begun in 1991, obstacles to upriver migration of fishes from cross-river structures such as weirs have been gradually improved. Along with these changes improvements have also been made along rivers that are not among the rivers in the model project. However, there remain many issues such as entrainment countermeasures, responses to high dams, and evaluations of type of fishways that require research and technology development, because some of this technology is still under development, and the spread and use of the technology in the field is still insufficient. In addition there are other types of issues, such as the fact that means for verifying the improvement results have not been systematized. When pushing ahead with future projects, spreading the experience and knowledge gained on the model rivers, conducting further surveys and investigations, and supporting flexible responses and devices at actual field sites will be indispensable.
