From the reports on the Tamshui River Watershed ecological investigation related works by Council of Agriculture, Environmental Protection Administration, Taipei City Government Department of Economic Development, Keelung Environmental Protection Bureau, Taipei Zoo, and etc., and the findings of this project, it is shown that more than 30 species of fish may be found, which implied the achievements and success of the 「Follow-up Plan for Tamshui River Cleanup」. From the literature reviews by this projects, species and amounts of halophilous fish in Tamshui River watershed were collected and sorted. These data were analyzed and compared with water quality factors. It appeared that under the same water quality conditions, the variation trend of peripheral division freshwater fish and marine fish in the mainstream of Tamshui River, the variation trend of primary and peripheral division freshwater fish in the lower reaches of Keelung River, the variation trend of peripheral division freshwater fish in the lower reaches of Dahan River, and the variation trend of primary and second division freshwater fish in the lower reaches of Shin-Dian River could be well explained. In addition, correlation analysis (F test, 90% confidence interval) of freshwater fish species and water quality factors were conducted for Tamshui River watershed. It appeared that concentrations of SS and DO have more direct and significant influence on the variation trend of freshwater fish species, while RPI and other water quality factors have less influence. On the work for oxygen enhancement experiments, information regarding domestic and international experiences of several measures to increase the dissolved oxygen concentration in the rivers or lakes has been collected. Besides, reviews on the addition of H2O2 to enhance dissolved oxygen concentration, aquatic chemistry and degradation on H2O2, laboratory work of 96-hour dose-response relationship on the H2O2 and selected species of fish, model simulation of the H2O2 concentration in the river as well as the cost-effective evaluation on the utilization of H2O2 as the oxygen enhancer had been implemented. From the results of this work, the degradation rate of H2O2 in Tamshui River water was found to be 0.40day-1; the results of dose-response relationship experiments showed that the concentrations of LC50 of Ambassis commersoni Cuvier in deionized water and groundwater were 69.74 and 73.44 mg/L, respectively; for the LC50 experiments of hybrid of Oreochromis mossambicus, it is found that all fish survived after 96-hours tests, at the water temperature of 16 and 20℃. From these results, it is suggested that the concentration of H2O2 should be controlled under the concentration of 60mg/L for the consideration of fish survival in the rivers if the addition of H2O2 is selected as the contingent method to increase the dissolved oxygen. For the guidance of the addition of H2O2 as the contingent method to increase the dissolved oxygen, chemical dosage and the location of chemicals addition is investigated based on the calculation modified Streeter-Phelps equation. In the contingency plan, the pattern for chemical addition may be either with the continuous addition or the instant addition pattern. The model simulation results showed that location for chemicals addition is closely related the hydraulic characteristics of the river. In the case study on Keelung River simulation, it is calculated that 6.5-hour traveling distance upstream to the point source is the best location for the oxygen enhancement agent addition.

fishery survey, Oxygen enhancement, Fish dose-response test