Abstract
Age and growth of the cyprinid fish Hemibarbus barbus in the Chikugo River were studied by interopercle reading of 316 specimens. Interopercle radii and ring radii were measured from the focus to the anterior edge and to outer margins of the hyaline zones, respectively. The relationship between interopercle radius and standard length was shown as a straight line. The outer margins of the hyaline zones as annual rings were formed once a year in April. Growth of this fish was expressed by the von Bertalanffy's equation as Lt= 519.7 [1-exp{-0.195(t+0.158)}] for males and Lt=571.3 [1-exp{-0.167(t+0.289)}] for females (Lt: standard length in mm, t: age).
Most of 1- to 3-year-old immature fish were found in the fresh water of the tidal reaches all the year round. The spawning run of this fish mostly comprised of 4- and 5-year-old groups from the tidal reaches to the reaches about 20km upstream occurred in April. Therefore it seems that the migration of H. barbus in the Chikugo River may be classified as potamodromous migration or fluvial migration.
