Abstract
Age, growth and maturity of the bagrid fish Pseudobagrus aurantiacus from the middle reaches of the Chikugo River, Kyushu Island, Japan were studied by examination of vertebral centrum and histological observations. Marginal increments of vertebral centrum formed annual rings from March to April. The growth of this fish was expressed by von Bertalanffy's equation as Lt=340.4[1-exp{-0.131(t+0.759)}] for males and Lt=266.8[1-exp{-0.146(t+0.920)}] for females, where Lt is standard length (SL) in mm and t is age in years. Males grow faster and live longer than females.
The spawning period of this population was considered to take place from July to August (mainly July). The minimum size at maturity was 77.6mm SL for males and 90.0mm SL for females. The age at which 50% of the fish reached maturity was 1-year-old for males and 2-year-old for females. The earlier maturity of males may be related to their faster growth.
