In Japan, many fishways have been designed and constructed on facilities which impede the movement of fishes, to facilitate their migration. Although the numbers of fishes migrating across fishways have been examined to evaluate fishways, such data is insufficient to verify the functions of fishways, because the number of migrating fish required in the ecosystem is not known. In this study, the objective of a fishway was defined as “preservation of the local population of fishes”, and the molecular biological method was used to evaluate fishways. Only three natural species of fish, White spotted char (Salvelinus leucomaenis leucomaenis), Wrinklehead sculpin (Cottus nozawae) and Stone loach (Barbatula barbatula), and one terminator species, Seema (Oncorhynchus masou masou), were found in a small drainage channel in Hokkaido along which there are 14 weirs over a 6-km length of the channel. Fin samples from 250 individuals of these species were collected over two years and preserved in 95% ethyl alcohol until DNA extraction using a phenol-chloroform extraction protocol after proteolysis by Proteinase K. The amplified fragment length polymorphisms (AFLP) method was applied. To estimate the genetic differentiation between populations in each area and between different generations, the genetic diversity and population genetic structure were estimated using AFLP SURV1, 2 and STRUCTURE3. The Phylip software package4 was used to generate a minimum spanning tree. The genetic structures of each species were similar throughout the river; only white spotted char showed some differences. It is suggested that this difference is not significant for the local population of White spotted char, because the difference disappeared after flooding. Furthermore, population differences between the dredge channel and branch could be detected for Wrinklehead sculpin and White spotted char. These results show that the molecular biological method can be used to evaluate fish migration, especially across fishways. |