AGE, GROWTH AND MATURITY OF THE BAGRID FISH PSEUDOBAGRUS-AURANTIACUS IN THE CHIKUGO RIVER, KYUSHU ISLAND, JAPAN

Age, growth and maturity of the bagrid fish Pseudobagrus aurantiacus f rom the middle reaches of the Chikugo River, Kyushu Island, Japan were studied by examination of vertebral centrum and histological observat ions. Marginal increments of vertebral centrum formed annual rings fro m March to April. The growth of this fish was expressed by von Bertala nffy's equation as L-t=340.4[1-exp{ -0.131(t+0.759)}] for males and L- t=266.8[1-exp{-0.146(t+0.920)}] for females, where L-t is standard len gth (SL) in mm and t is age in years. Males grow faster and live longe r than females. The spawning period of this population was considered to take place from July to August (mainly July). The minimum size at m aturity was 77.6 mm SL for males and 90.0 mm SL for females. The age a t 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 t o their faster growth.