有明海周辺河川におけるヤマノカミの分布と生活史
1994 年 41 巻 2 号 p. 123-129
詳細
1994 年 41 巻 2 号 p. 123-129
The distribution and life history of the catadromous cottid fish, Trachidermus fasciatus were studied in rivers discharging into Ariake and Yatsushiro Sounds, west Kyushu, Japan. The fish were found to inhabit rivers located between the Yabe River of Fukuoka Prefecture and the Honmyo River of Nagasaki Prefecture. Juveniles were found in May pointing upstream just below dams which were located at the lowest point in the rivers. Until their first autumn, the fish remained in small areas below the dams. Most of the dams were located at the upper end of the tidal reaches of the rivers. We did not find T. fasciatus inhabiting areas above the lowest dam. Their present distribution, which is restricted down-stream and confined to unnaturally small areas, is thought to be caused by the construction of the dams. The fish do not appear to migrate as far upstream as previously reported. The fish mature and migrate downstream in their first autumn or winter, when they are about 150 mm in total length. No age 2 fish were found in the rivers surveyed. Juveniles smaller than 19mm in total length mainly fed on copepods, and their main food changed from aquatic insects to fish after their upstream migration.
