Bull. Jpn. Soc. Fish. Oceanogr. 75(1), Page 9-18, 2011   Seasonal Variation of Primary Productivity in Shitaba Bay of Uwa Sea, Japan Azumi Yamashita1†, Kazuo Iseki2, Kenji Tarutani3 and Yoshitsugu Koizumi1 1 Center for Marine Studies, Ehime Prefectural Research Institute for Agriculture, Forestry and Fisheries, Shitaba, Uwajima, Ehime 798-0104, Japan 2 Graduate School of Biosphere Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan 3 National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Maruishi, Hatsukaichi, Hiroshima 739-0452, Japan  † yamashita-azumi@pref.ehime.jp Primary productivity in the Shitaba Bay of Uwa Sea was measured by the in situ 13C tracer method one to three times a month for three years from February 2002 to January 2005, together with the hydrographic observation and chlorophyll a and nutrients analysis. The depth-integrated primary productivity ranged from 0.11 gC m-2 day-1 to 1.83 gC m-2 day-1 during the observation, and the annual primary productivity was estimated to be about 193 gC m-2 year-1. The productivity was highest in summer (0.82 gC m-2 day-1) throughout the year, followed by that of autumn (0.68 gC m-2 day-1), spring (0.44 gC m-2 day-1), and was lowest in winter (0.18 gC m-2 day-1). There was a correlation (r=0.77, p<0.01) between the primary productivity and depth-integrated chlorophyll a (mg m-2) throughout the year, and high correlation (r=0.96, p<0.01) was found in autumn but no correlation was found in summer. The chlorophyll a specific productivity generally tend to increase with the surface irradiance, but in summer the chlorophyll a specific productivity was considerably variable, probably due to the different nutrient availability. High chlorophyll a specific productivity may be linked to the intrusion of bottom water, which may play an important role in supporting the biological productivity of Shitaba Bay. Key words: centrum, first maturation, growth, spawning period, yellowtail, Seriola quinqueradiata