Abstract:The spatial and abundance patterns of Parathemisto gaudichaudi (Amphipoda) were investigated in the Changjiang Estuary (29°00′-32°00′N, 122°00′-123°30′E) between 1959 and 2002. The species′ ecological group was classified and its optimal temperature calculated through the analysis of concurrent abundance and environmental data collected during the cruises and application of a mathematical model. Relationships between abundance variation between years and global warming were then analyzed for the Changjiang Estuary. The results revealed a distinguished seasonal change in both abundance and frequency of occurrence for Parathemisto gaudichaudi in the Estuary; both were higher in spring and winter than in summer or autumn. Average abundance in 1959 was highest in spring and lowest in autumn (18 ind/m3 and 0.03 ind/m3, respectively). Frequency of occurrence was highest (62.96%) in spring and lowest (690%) in autumn. The clumping index for Parathemisto gaudichaudi in the Changjiang Estuary was higher in spring (7.1) than in autumn (-1.0) in 1959, which indicated that the species showed clear aggregation in spring. The optimal temperature for Parathemisto gaudichaudi in the Changjiang Estuary was about 17 ℃, as calculated from the Yield Density model (P=00001). Based on its optimal temperature and seasonal abundance variation, Parathemisto gaudichaudi could be classified as a temperate water species. The spring abundance of Parathemisto gaudichaudi had clearly decreased between 1959 and 2002 and the decline may be related to global warming in the Changjiang Estuary. Parathemisto gaudichaudi could be regarded as an important indictor species for global warming in the area.