Age, growth, reproductive season, feeding habit, and dispersion of largemouth bass Micropterus salmoides were studied using 202 specimens collected in the Hija River of Okinawa Island from 2005 to 2007. The ages determined by otolith analysis ranged from 0.42 to 3.67 year-old and the mean standard length of 1 year-old individuals was 134 mm and that of 2 year-old ones was 183 mm. They were estimated to breed mostly from January to April by monthly changes in gonadosomatic index and of water

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... erature. The examination of their stomach contents showed that most of their foods were alien species, such as Oreochromis spp. and Palaemon paucidens, but Monopterus albus, an endangered species in Ryukyu Islands was also found. It was supposed that the largemouth bass reproduced in the Kurashiki Dam Reservoir and a part of them fl owed out with occasional overfl ows from there and dispersed over the whole Hija River system.