Abstract
Swimming experiments were conducted in the field using weather loach (Misgurnus anguillicaudatus) fry in order to study its swimming ability. The experimental equipment used was a stamina tunnel, which was installed at a local dry riverbed. During one swimming experiment, the relationship between swimming speed and time, and the relationship between velocity and swimming distance were considered. For weather loach with body lengths of between 4 cm and 5 cm, the results show that 1) a swimming-curve-formula defining the relationship between swimming speed and swimming time was obtained, 2) swimming time of the weather loach whose body length is between 4 cm and 5 cm was shorter than those whose body length is more than 5 cm in the same flow velocity conditions, 3) the critical flow velocity in which the weather loach could swim up was 43-55 cm•s-1, and 4) in the case of a small scale fishway for fishes in paddy field design for weather loach in which the flow velocity in the small scale fishway for fishes in paddy field is made to be 30 cm•s-1 or about 40 cm•s-1, many individuals seem to be able to ascend, as the necessary passage distance was respectively made to be 30 cm or less and 10 cm or less.
