Did multiple handmade fishways contribute to salmonid fish habitat recovery?

Abstract

Effects of multiple fishways made by citizens on the fish community and the redds were examined in the Komaoi River of the Abashiri River system in eastern Hokkaido. Before installing fishways, in the river section above artificial drop structures any salmonid fish nor any redd were found but Cottus nozawae and Lethenteron sp. were present. After having installed seven handmade fishways in 2012, fish of Salvelinus leucomaenis and Oncorhynchus masou masou and their redds were observed at the river section. On a quantitative investigation at the river section in 2013 O. m. masou was the only collected salmonid species. In 2017 O. m. masou and S. leucomaenis were collected. Meanwhile, the number of C. nozawae seems to be decreased after fishway installations. These results clearly show that multiple handmade fishways installed to the Komaoi River enable the upstream migration of salmonid fish to above artificial drop structures. However, due to river bank protection at the middlestream region, it might cause the delay in the population recovery of a sedentary fish.