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Based on the long?term datasets for the period of 1915～2005 from various sources, effects of water temperature and water chemistry on the fish in the Thames Tideway were assessed. There was a steady rise in temperature in the upper and middle reaches before 1960s. After that the temperature dropped in the upper and middle reaches while it increased in the lower reach. These patterns were influenced by the thermal discharge from power stations. Temperature was negatively correlated with average individual fish numbers and dissolved oxygen (DO) with Spearman’s rho of -0.468 and -0.607 (p< 0.05 ) respectively. The fact that high BOD and ammonia and low dissolved oxygen coincided with no presence of fish prior to 1960s while return of fish corresponded to the marked rise in dissolved oxygen and decrease in BOD as well as ammonia indicated that pollution was the main factor influencing fish over the long period. Climate change may have affected the fish community; however it was assumed that it influenced fish more likely through changing the freshwater flow and tide regime in the tideway. It may be difficult to assess the effects of every single factor on fish in the tideway because they were more synergistic than that in other water bodies; thus, further studies on the factors influencing the improvement in ecological status will be necessary.
Based on the long? Term datasets for the period of 1915 ~ 2005 from various sources, effects of water temperature and water chemistry on the fish in the Thames Tideway were assessed. There was a steady rise in temperature in the upper and middle reached before 1960s After that the temperature dropped in the upper and middle reaches while it increased in the lower reach. These patterns were influenced by the thermal discharge from power stations. Temperature was negatively correlated with average individual fish numbers and dissolved oxygen (DO) with Spearman’s rho of -0.468 and -0.607 (p <0.05) respectively. The fact that high BOD and ammonia and low dissolved oxygen coincided with no presence of fish prior to 1960s while return of fish corresponded to the marked rise in dissolved oxygen and decrease in BOD as well as ammonia pointed that pollution was the main factor influencing fish over the long period. climate change may have affected the fish community; however it was considered t hat it influenced fish more likely through changing the freshwater flow and tide regime in the tideway. It may be difficult to assess the effects of every single factor on fish in the tideway because they were more synergistic than that in other water bodies; thus, further studies on the factors influencing the improvement in ecological status will be necessary.